Interagency Levee Policy Review Committee
Washington, DC




September 1, 2006
Matthew B. Miller, P.E. 
Chief, Risk Analysis Branch 
Mitigation Division 
Federal Emergency Management Agency 
Washington, DC 20472
Dear Mr. Miller:
Attached is the report of the Interagency Levee Policy Review Committee, which was prepared in 
accordance with Federal Emergency Management Agency (FEMA) Contract No. HSFEHQ-04-D-
0025, Task Order No. HSFEHQ-05-J-0008, Michael Baker Jr., Inc.
This report:
*	Examines current FEMA levee policies, as stated in 44 CFR 65.10 and FEMA guidance 
documents, and recommends, as appropriate, changes to these policies
*	Identifies public awareness and outreach challenges in the conduct of levee remapping and 
proposes approaches to be taken to deal with these challenges
*	Proposes cooperative development by FEMA and the U.S. Army Corps of Engineers of a 
Geographic Information System-based levee inventory

The report has been coordinated with Federal agencies represented on the Interagency Committee.
We are prepared, at your convenience, to brief you or your staff on the details of the report.

 			 
Gerald E. Galloway, Ph.D., P.E.			Kelly A. Bronowicz, CFM 
Consultant, Michael Baker Corp.		FEMA Mitigation Division 
Committee Chair				FEMA Project Leader




The National Levee Challenge

Levees and the FEMA Flood Map Modernization Initiative




Report of the  
Interagency Levee Policy Review Committee















September 2006




Table of Contents

Executive Summary	ES-1
1.	Levees and the FEMA Flood Map Modernization Initiative	1
1.1.	The Levee Challenge	1
1.2.	The Interagency Levee Policy Review Committee	2
1.3.	Levees and the NFIP	3
2.	The Role of Levees in the NFIP	7
2.1.	Mapping of Protected Areas	7
2.2.	Roles and Responsibilities	7
2.3.	Levee Design, Certification, and Accreditation	8
2.4.	The Early Days	8
2.5.	The Brooks Amendment and the Establishment of A99 Zones	9
2.6.	FEMA’s 1981 Interim Levee Policy and Issuance of 44 CFR 65.10	10
2.7.	National Research Council Report	10
2.8.	Establishment of Flood Control Restoration Zones (Zone AR )	12
2.9.	Midwest Flood of 1993	13
2.10.	Hurricane Katrina	14
3.	FEMA Requirements for Mapping Levees: Challenges, Opportunities, and Options	17
3.1.	Current FEMA Requirements for Mapping Levees	17
3.1.1.	Regulatory Requirements	17
3.1.2.	FEMA Guidelines and Specifications for Flood Hazard Mapping Partners	19
3.1.3.	FEMA Procedure Memoranda	20
3.2.	Challenges and Issues with Current Requirements and Policies	21
3.3.	Conclusions	24
3.4.	Recommended Changes to FEMA Levee Mapping Requirements (and Attendant 
Levee Certification)	24
3.4.1.	Regulatory Changes	25
3.4.2.	Guidelines and Specifications for Flood Hazard Mapping Partners	26
3.4.3.	FEMA Procedure Memoranda	27
4.	Levee Height and Structural Integrity - The Role of Risk Analysis Methodologies	29
4.1.	Determination of Levee Height	29
4.2.	Freeboard	29
4.3.	USACE Risk Analysis Approach – 1996	30
4.4.	Implementing Risk Analysis Concepts in 44 CFR 65.10	31
4.5.	Conclusion	31
4.6.	Recommendation	31
5.	Computation of the 1-Percent-Annual-Chance Flood – Problems and Solutions	33
5.1.	Precipitation Frequency Estimates	33
5.2.	Estimating Flow Frequency	36
5.3.	Conclusion	37
5.4.	Recommendation	37
6.	Levee Inventory Database	39
6.1.	Existing Levee Inventory Systems and Databases	39
6.1.1.	FEMA Levee Inventory System	39
6.1.2.	Current FEMA DFIRM Data	40
6.1.3.	State Databases	40
6.2.	Levee Inventory Systems and Databases under Development	40
6.2.1.	California DWR Levee Database	40
6.2.2.	U.S. Army Corps of Engineers	41
6.2.3.	FEMA GIS Database	41
6.3.	Conclusion	42
6.4.	Recommendation	42
7.	Decertification of a Levee	43
7.1.	Levee Decertification	43
7.2.	Use of Zones AR and A99	44
7.3.	Recognition of and Dealing with the Impact of Decertification	46
7.4.	Conclusions	46
7.5.	Recommendations	47
8.	Public Awareness and Outreach	49
8.1.	FEMA and Outreach	49
8.2.	Strategy Development and Implementation	50
8.2.1.	Awareness and Outreach Approach	50
8.3.	Conclusion	52
8.4.	Recommendations	52
9.	Handling of Counties Where Maps Have Become Effective	53
10.	Overarching Issues	55
10.1.	Level of Protection	55
10.2.	Dealing with Residual Risk	56
10.3.	Future Conditions	57
10.4.	System Reliability	58
10.5.	Federal, State, and Interagency Cooperation	58
10.6.	Research and Development – Geotechnical Assessment    of Levee Integrity	58
11.	Next Steps	61
11.1.	Immediate Actions	61
11.2.	Longer-term Actions	62
Appendix A.	Interagency Levee Policy Review Committee Membership	A-1
Appendix B	44 CFR §65.10	B-1
Appendix C.	Proposed Revisions to 44 CFR §65.10, Mapping of Areas Protected 
                        by Levee and Floodwall Systems	C-1
Appendix D.	Public Awareness and Outreach Approach	D-1
Appendix E	Levee Database Framework Design Recommendations	E-1
Appendix F.	FIRM Map Zone Designations	F-1
Appendix G.	List of Acronyms	G-1
Appendix H	References	H-1




Report of the
INTERAGENCY LEVEE POLICY REVIEW COMMITTEE

Executive Summary

1.  Levees, the National Flood Insurance Program, and Flood Map 
     Modernization
Levees are earth embankments constructed along rivers and coastlines to protect adjacent lands 
from flooding.  Floodwalls are concrete structures designed for urban areas where there is 
insufficient room for levees.  Both levees and floodwall are important components of the flood risk 
reduction systems of many flood-prone communities across the Nation and, over the years, have 
prevented billions of dollars in damages to property and protected millions of people from the threat 
of floods.
However, some levees and floodwalls and their appurtenant structures, when stressed beyond their 
capabilities to withstand floods, have failed with catastrophic results, as seen during Hurricane 
Katrina.  The Department of Homeland Security’s Federal Emergency Management Agency 
(FEMA) currently estimates that levees are found in approximately 22 percent of the Nation’s 3,147 
counties.  Forty-three percent of the U.S. population lives in counties with levees.  
Dealing with areas “protected” by levees has been a critical issue for the National Flood Insurance 
Program (NFIP) since it was established by the National Flood Insurance Act of 1968.  When the 
NFIP was established, thousands of individual levees existed across the United States, ranging from 
flood control projects with known levels of damage/risk reduction and well-documented engineering 
to small agricultural levees constructed by individual farmers.  If FEMA determines that a levee can 
be accredited as providing protection from the 100-year flood , those living behind the levee no 
longer must comply with NFIP requirements for regulation of floodplain activity and mandatory 
purchase of flood insurance.   The challenge has been how to determine which levees should be 
recognized as providing protection from the 100-year flood and, once accredited, how to ensure that 
those accredited levees continue to provide 100-year protection and that the residual risk is 
effectively managed.
In 2004, as it initiated work under the Flood Map Modernization initiative (Map Mod), FEMA 
determined that analysis of the role of levees in flood risk reduction would be an important part of 
the efforts of Map Mod and directed the conduct of a scoping study to analyze the challenges to 
Map Mod and the NFIP that would be encountered as the Map Mod program progressed.  The 
study group’s report, issued in spring 2005, noted that the status of the Nation’s levees was not well 
understood and the condition of many levees and floodwalls had not been assessed since their 
original inclusion in the NFIP.  
As it began work on the Map Mod initiative, FEMA determined that information developed for 
remapping of some levees revealed that those levees might no longer be in compliance with FEMA 
regulations, and that this would lead to the decertification (removal of accreditation) of these 
levees.   FEMA also determined that, in other cases, insufficient information was available on which 
to base an immediate determination of certifiability.  If a levee was decertified, the residential 
structures behind that levee would be subject to mandatory flood insurance purchase requirements 
and additional floodplain regulation.  FEMA determined that it needed to better assess the current 
status of its regulations and guidance and to examine the potential impacts of levee mapping on the 
Map Mod program. 
2.  The Interagency Levee Policy Review Committee
In September 2005, FEMA established the Interagency Levee Policy Review Committee to review 
current levee policy as articulated in Title 44 of the Code of Federal Regulations Section 65.10, 
Mapping of Areas Protected by Levees  (44 CFR 65.10).  The committee was asked to 
recommend changes to that policy, including outlining the rationale to support those changes and 
identifying any required revisions to FEMA regulatory or guidance documents and insurance rating 
practices. The committee was also charged with proposing a public awareness strategy to inform 
stakeholders of any changes in policy and the public’s role in its implementation, and with overseeing 
development of a draft Geographic Information System framework for a national inventory of levees 
that would contain or provide access to pertinent data.
The committee first met in November 2005.  Committee membership included representatives of the 
principal Federal agencies that deal with the flood damage reduction activities.  Representatives of 
appropriate State and nongovernmental organizations were asked to participate in discussions of 
topics relevant to their expertise and interests.  The committee met in person (with some members 
participating by telephone) eight times and coordinated preparation of its report through electronic 
mail and additional conference calls.  During its deliberations, the committee was briefed by Federal 
agencies and State and other organizations on activities related to levee issues.  Members of the 
committee conducted research into specific topics as needed. 
This committee report addresses the current criteria for evaluating levees under the NFIP, the 
procedures for applying these criteria to certain situations, and the impact those actions have on the 
local community, Map Mod, and the NFIP.  The report also recommends actions to be taken when it 
was found that current criteria and procedures need to be revised.
3.  Conclusions and Recommendations
Based on its review, the committee developed conclusions and recommendations concerning the 
treatment of levees in the NFIP and in execution of the Map Mod initiative and the need for 
modifications to current approaches.  These conclusions and recommendations are summarized in 
the following paragraphs
Identification of the Risk behind Levees
Levees only reduce the risk to individuals and structures behind them; they do not 
eliminate the risk.  In fact, in many cases, they can create significant and potentially 
catastrophic residual risk that may increase if conditions in the region change, if the 
levees are affected by natural events, or if the levees are not properly maintained.  Levees 
should be considered as flood risk reduction structures, not flood protection structures, and 
should be treated accordingly.  A structure that is elevated to the 100-year Base Flood Elevation 
(BFE) faces significantly less risk than an unelevated structure built behind a 100-year levee.  
To ensure that the public and public officials are aware of the risk to the areas behind levees, 
FEMA should define a new flood insurance zone (Zone XL) for areas behind levees that 
provide 100-year protection and meet other requirements for inclusion in the NFIP and, in 
coordination with other agencies, identify the level of risk to those structures behind 
those levees.  
The XL zone would include those areas behind the levee that are subject to inundation by the 
100-year flood in the without-levee condition.  The area between the 100- and 500-year floodplain 
lines would be shown as a shaded X zone.  
Levees would also be identified under a scientifically based levee risk classification system (e.g., 
high, medium, or low).  This classification system would be based on several factors, including the 
following:
*	Potential depth of flooding in the event of failure or overtopping
*	Type and density of development in protected areas behind the levee
*	Steps taken to ensure that levee failure does not occur during levee capacity exceedance 
(overtopping)
*	Warning times
*	The number and types of egress so that people who may be inundated may move out of 
harm’s way

This levee risk classification would be designated on the Flood Insurance Rate Map (FIRM) and in 
the Flood Insurance Study report. 


Improvement of Regulations Governing Levees in the NFIP
Current regulations and other guidance for recognition and mapping of levees in the NFIP 
are not adequate for making the initial determination that a levee meets minimum design, 
operation, and maintenance standards, and ensuring that it continues to meet standards.  
The regulations and guidance do not provide adequate oversight of a levee’s continued conformance 
with NFIP criteria.  Therefore, the regulations may permit inclusion and/or retention in the NFIP of 
levees that do not provide the required level of protection.
To ensure that levee systems maintain the conditions that qualified them for NFIP 
accreditation, FEMA should require as a condition of retaining FEMA recognition of 
levee status that sponsors:
*	Conduct annual inspections of the levee system
*	Submit to FEMA biennially the results of the annual inspections, levee system operation and 
maintenance records, and an assessment of the levee system during any flood events that 
occurred within the reporting period
*	Submit to FEMA every 10 years a report, prepared by a registered Professional Engineer or 
Federal agency responsible for levee design, that recertifies the engineering and geotechnical 
conditions of the levee system
*	Certify levees as systems that include not only levees and floodwalls, but also the pumps, 
interior drainage systems, closures, penetrations, and transitions that provide systems 
integrity, and ensure that operation and maintenance plans cover all elements of the system

To ensure that all components of a levee system meet required standards, FEMA should 
exclude embankments, such as roads and railroads, from inclusion in accredited levee 
systems unless those embankments meet the engineering criteria required of levees and 
are maintained and operated in accordance with the provisions of 44 CFR 65.10.
FEMA should revise 44 CFR 65.10 to incorporate the above recommendations and to 
deal with other needed changes in the administrative requirements of 44 CFR 65.10 as 
noted in the appendices to this report.
Development of a Levee Inventory 
Information about the location and condition of levees across the Nation is spotty and is 
not in a form that supports effective management and decision making.  
Various levee databases have been developed, but for the most part they are not geospatially 
referenced, are incomplete, and lack usable information concerning the condition of the levees and 
attendant supporting structures.  Current efforts by the U.S. Army Corps of Engineers (USACE) 
and FEMA to coordinate and develop a multi-agency, Federal-State approach to inventory and 
assessment promise to provide significant benefits. 
FEMA and USACE should continue their efforts to develop a joint database structure that 
will meet the needs of both agencies and other Federal and State organizations to maintain 
an inventory and assessment of flood damage reduction structures, including levees. 
While agency-specific components of such a database will be needed, the management and fiscal 
benefits that accrue from a common core and adherence to the national spatial data infrastructure 
(NSDI) will be significant.
Improving Public Understanding of Levee Risks
The public at large and public officials generally do not understand the residual risk to 
those living behind levees.  The public also does not understand that FIRMs provide information 
only about levees that have been recognized by the NFIP and not information about the existing risk 
to structures located behind those recognized levees.
Working with its Federal, State, and local partners and with levee sponsors, FEMA should 
develop and implement a public awareness and outreach strategy that will improve public 
awareness and understanding of the hazards and risks associated with levees.  This 
audience includes the Administration and Congress, other public officials, and private 
citizens.
As part of this public outreach effort, levee sponsors should be required to notify annually property 
owners in areas behind a levee about the residual risk that exists and the risk classification of the 
levee. 
Enhancing Institutional Relationships
The relationships among institutions and organizations dealing with levees are not clearly 
defined and vary by agency and region.
The Federal Government's role in flood damage reduction through USACE, the Natural Resources 
Conservation Service (NRCS), the Bureau of Reclamation, the National Oceanic and Atmospheric 
Administration (NOAA), and the U.S. Geological Survey (USGS) is generally understood.  FEMA’s 
role in floodplain management is evolving and is less understood by the public.  Similarly, the role of 
State and local organizations in carrying out floodplain-related activities is evolving. 
Success in Map Mod as well as flood damage reduction will depend on the development of close 
working relationships among representatives of the agencies involved.  
Efforts should be made to closely coordinate the activities of relevant Federal agencies in 
floodplain management and related mapping programs.
Assisting Communities following Levee Decertification
The process of conducting certification activities and, if required, restoration of 
decertified levees will place a heavy burden on local communities.  
These communities are already turning to the Federal Government for support, and the Federal 
Government should expect these requests to increase.  These requests will place heavy burdens on 
related FEMA and USACE programs that are already fiscally stretched thin.
FEMA and USACE should review existing authorities and funding available to assist 
communities in performing certification analysis and make recommendations to the Office 
of Management and Budget (OMB) if the funding and authorities are not available.  
FEMA and USACE also should develop expedited processes to assist communities in 
remediation of publicly owned levees and seek OMB and Congressional approval of these 
processes and the need for resource commitments to support them.
FEMA should consider seeking legislative action to permit use of A99 designation and 
procedures by communities that are able to self-fund levee upgrades.
Ensuring 21st Century Levee Design
Much of the baseline information that is used in determination of the height of the 100-
year flood is out of date.  The engineering community is replacing the current levee-
height determination methodology required by 44 CFR 65.10 with new approaches.  As a 
result, levee designs and flood risk determinations may not reflect current conditions; this could 
increase the flood hazard risks to those behind levees and in the floodplain.
To ensure that the base data used to support the hydraulics and hydrology (H&H) analysis are up to 
date and reflect 21st-century computation technologies, FEMA, in coordination with other 
Federal agencies that use these data and techniques, should support funding of NOAA 
efforts to upgrade precipitation frequency estimates, upgrades to the USGS gaging 
program, and the Advisory Committee on Water Information Subcommittee on Hydrology 
revision of Bulletin 17B, which guides flood recurrence interval determinations.
Recognizing the national and international movement toward use of risk analysis in dealing with 
floods and their consequences, the significant strides that have been made in developing risk 
assignment techniques, and the current use of these techniques by USACE in levee design, FEMA 
should modify 44 CFR 65.10 to phase out, over the next 10 years, use of the freeboard-
based approach and should substitute the risk analysis methodology for levee-height 
determination.  During the transition period, FEMA should permit either approach to be used in 
levee design and recertification analysis.
4.  Observations
In the course of its review, the committee encountered issues that did not specifically relate to the 
challenges faced by the Flood Map Modernization program, but in the committee’s opinion, these 
issues should be brought to the attention of FEMA and would merit action by FEMA.
a.	Strong consideration should be given to not recognizing, for NFIP purposes, levees that provide 
protection to highly urbanized areas unless they provide protection against floods greater than 
100 years (e.g., the 500-year flood).  There is a long history of recommendations and analyses 
to support protection to 500-year or greater levels.  Given the large number of existing levees, 
the transition would not be quick or easy.  Nevertheless, FEMA should take steps to 
immediately examine this issue in detail and determine if a change in the standard for 
recognition should take place.
b.	Non-Federal levees exist at the sufferance of the States and counties in which they are located.  
Federal levees, for the most part, are passed to State and local sponsors following their 
completion for operation and maintenance.  State and local agencies must play a significant role 
in dealing with levee issues as they arise.  Federal agencies should recognize the State and local 
roles and develop incentives and support mechanisms to ensure that State and local agencies 
can effectively carry out their responsibilities.
c.	Property owners behind levees continue to face the residual risk of flooding, yet they are not 
required to share in the mitigation of this risk through insuring their property against the dangers 
of the residual risk.  FEMA should address the challenge of the residual risk in the following 
ways:
?	Seeking legislative change to require property owners to purchase some level of flood 
insurance for structures behind levees (new Zone XL). 
?	Requiring communities to establish special early warning systems and to develop flood 
warning – preparedness plans for those areas that are protected by levees.
d.	The current H&H approach for calculation of the BFE ensures that structures being designed 
to comply with the BFE are out of date by the time they are constructed.  Future H&H 
conditions are not directly addressed.  FEMA, working closely with other Federal agencies, 
States and communities, should examine how best to deal with climate change, sea-level rise, 
and future development.  Such efforts will require the commitment of significant resources.  It 
also represents a conceptual shift from specifying the mapping criteria to reflect present 
conditions to establishing criteria based on possible, but not fully quantifiable, future conditions.  
e.	When communities are not able to document immediately the recertifiability of currently 
certified levees and the levees are not known to be at risk, FEMA should notify the 
communities of the need for a more detailed examination of the levees and provide a specific 
schedule for that activity.  Communities should be required to notify all residents who are living 
in areas behind the levees of the re-examination and identify for them the residual risks and the 
need for information about the levees.  This action would closely parallel ongoing FEMA efforts 
to permit completion and adoption of new countywide maps that contain levees needing further 
study.
f.	A major challenge facing those responsible for levee certification is conduct of appropriate and 
rapid geotechnical assessments of levee integrity.  These assessments are critical to providing 
assurances of levee safety.  However, such assessments, depending on the nature of the 
material and the cross section of the levee, are very costly.  The bulk of the costs are related to 
the number and depth of soil borings.  While some research is underway in Japan and the 
Netherlands on use of remote electro-magnetic sensors, no methods or technologies are 
currently available in the United States to replace soil borings, and little effort is underway in the 
Research and Development (R&D) community to deal with the challenge.  FEMA, USACE 
and USGS should support R&D efforts focused on improvement of rapid assessment of levee 
geotechnical integrity and should jointly recommend to the National Science Foundation that 
attention be given to this area of research.

5.  The Challenge Ahead
The committee recognizes that the recommendations and observations it has offered will require 
significant resource commitments at both the Federal and State levels.  In a period of intense 
pressure on budgets, such proposals certainly will not be well received.  The issue, in reality, is one 
of “pay me now or pay me later.”  The harsh truth about levees is their potential for eventual failure.  
It is incumbent on leaders at all levels of government to argue forcefully for dealing with those 
issues now, while costs are far less than they might be in the future when another Katrina-type 
event occurs.




1.	Levees and the FEMA Flood Map Modernization 
Initiative
1.1.	The Levee Challenge
Levees are earth embankments constructed along rivers and coastlines to protect adjacent lands 
from flooding, as shown in figure 1-1.  Floodwalls are concrete structures designed for urban areas 
that have insufficient room for levees, as shown in figure 1-2.  Both levees and floodwalls, together 
with the pumps and drainage equipment that complete a levee system, are important components of 
the flood risk reduction systems of many flood-prone communities across the nation.
Over the years, these systems have prevented billions of dollars in damages to property and have 
protected millions of people from the threat of floods.  However, some levees and floodwalls and 
their appurtenant structures have been stressed beyond their capabilities to withstand floods and 
have failed—with catastrophic results.  The Department of Homeland Security’s Federal 
Emergency Management Agency (FEMA) currently estimates that levees are found in 
approximately 22 percent of the nation’s 3,147 counties.  Forty-three percent of the population lives 
in counties with levees. 
 
Figure 1-1.  Levee Cross Section


 
Figure 1-2.  Floodwall Cross Section.  In this figure, the floodwall is supported by piles and a 
sheet pile wall. Other floodwalls are supported only by a concrete “T” or similar base.

In July 2004, as it initiated work under the Flood Map Modernization (Map Mod) initiative, FEMA 
determined that analysis of the role of levees in flood risk reduction would be an important part of 
the efforts of Map Mod.  At that time, FEMA directed the initiation of a scoping study to analyze 
the challenges to Map Mod and the National Flood Insurance Program (NFIP) that would arise as 
Map Mod progressed.  The study group’s report, issued in spring 2005, noted that the status of the 
Nation’s levees was not well understood, and the condition of many levees and floodwalls had not 
been assessed since their original inclusion in the NFIP.  This report recommended undertaking a 
more detailed study and issuing interim guidance to Map Mod participants on how to deal with 
levees.  In August 2005, FEMA codified this guidance in Procedure Memorandum 34.
1.2.	The Interagency Levee Policy Review Committee
In September 2005, FEMA established the Interagency Levee Policy Review Committee to 
examine the levee situation and directed the committee to:
*	Review current levee policy as articulated in 44 CFR 65.10 and recommend changes to the 
policy, including the rationale supporting those changes and the identification of suggested 
modifications to FEMA regulatory or guidance documents and insurance rating practices
*	Prepare a public awareness strategy to inform stakeholders of any changes in policy and 
their roles in its implementation
*	Oversee development of a draft Geographic Information System (GIS) framework (for a 
national inventory of levees containing or providing access to pertinent data)

FEMA also directed the committee to prepare a report that would:
*	Identify potential problems, if any, with current policy and give examples of situations that 
manifest those problems
*	Discuss the need, if appropriate, for regulatory changes and provide the reasoning behind 
any recommended changes and an implementation concept
*	Provide recommendations regarding the application of the suggested levee policy to counties 
that already have modernized maps
*	Discuss the need, if appropriate, for revisions to insurance rating practices in areas protected 
by levees and provide the reasoning behind any recommended changes and an 
implementation concept

Committee participants are listed in Appendix A.
1.3.	Levees and the NFIP
The flood damage/risk reduction that a levee system provides is a function of the levee crown’s 
elevation along its entire length, the levee’s structural integrity, the stage (i.e., the height) of the flood 
against which the levee is designed to provide protection, and the functioning of the appurtenant 
structures.  Over time, all four of these elements are subject to substantial change, thereby changing 
the level of damage/risk reduction originally ascribed to the levee system.  When levee systems fail 
because of structural or foundation problems, or when they are overtopped and the embankment 
erodes to failure stage, the results can be catastrophic.  Depending on the topography, the depth of 
water in the flooded area can rise from 0 feet to more than 20 feet in a matter of minutes and that 
water remain trapped behind the levee for an extended period of time.  (Ground levels for sections 
of some levee-protected areas in California are more than 20 feet below the top of the levee.  Much 
of the New Orleans area that lies behind levees is at or below sea level and is subject to deep 
flooding.)
The goals of the NFIP, established by the National Flood Insurance Act of 1968, as amended, are:
*	To better indemnify individuals for flood losses through insurance
*	To reduce future flood damages through State and community floodplain management 
regulations
*	To reduce Federal expenditures for disaster assistance and flood control

FEMA has also established, as an implied goal for the NFIP, the restoration and preservation of the 
natural and beneficial values of floodplains.
The NFIP implements its insurance ratings and requirements for land use controls through Flood 
Insurance Rate Maps (FIRMs).  The FIRMs are also used by Federal agencies and lenders to apply 
the mandatory flood insurance purchase requirement of the NFIP.  Although these maps are 
produced for insurance and regulatory purposes, they are often the only existing form of flood 
hazard mapping for a community.  They are used by many communities and agencies as a guide for 
other flood-related activities.  In effect, these maps represent the principal means by which the 
Federal government communicates flood risk to the public.
When an area behind a levee that provides damage/risk reduction from the 100-year flood  is 
shown on a FIRM, that area is considered to be outside the 100-year floodplain.  Residents in these 
protected areas are not required to obtain flood insurance, and the community is not required to 
apply FEMA floodplain management regulations to the area.  44 CFR 65.10 provides criteria for 
determining whether the NFIP should recognize a levee for the purposes of removing the protected 
area from the floodplain.  Communities requesting official recognition of their levees must submit 
certification by a professional engineer that the levee meets the requirements of 44 CFR 65.10, or 
they must demonstrate that a Federal agency has indicated that the levee meets the NFIP standard.
Formal certification of levees began in 1982.  Prior to that date, levees were included in the NFIP 
when FEMA, another Federal agency, or a local sponsor indicated that the levee met general 
engineering standards for levees.
Over the past decade, Federal and State agencies have studied the hydrology and hydraulics (H&H) 
in many areas where levees provide damage/risk reduction.  New and better data and modern 
techniques have led to significant revisions of their estimates of the 100-year flood stage.  (In some 
areas along the lower Missouri River, the height of the 100-year flood has been recalculated and is 
as much as 4 feet higher in some reaches than is shown in current flood maps.  It is also as much as 
2 feet lower in other reaches.)  The 100-year stage represents the Base Flood Elevation (BFE) used 
to establish floodplain regulation and insurance under the NFIP.  A major factor in many of the 
increases in elevation across the Nation has been the increase in frequency and magnitude of large 
floods, many of which have caused failure or overtopping of levees.  In addition, over time, through 
subsidence or partial levee failures, the profile and integrity of many levees have deteriorated.
In 2004, FEMA initiated Map Mod to digitize and update its FIRMs over a 5-year period.  When a 
levee is shown on a map panel that is undergoing revision, FEMA faces one of three situations.
*	Information is available to verify that the levee is in good condition and provides the level of 
damage/risk reduction shown.  (The area can be mapped with levee protection included.)
*	Information is available to verify that the levee does not (or never did) provide the required 
level of damage/risk reduction.  (The area “protected” by the levee is mapped as if the levee 
does not exist, and the residents behind the levee will be required to obtain flood insurance 
and to comply with FEMA floodplain management regulations.)
*	Available information is inadequate to determine the status of the levee, other than its 
previous inclusion on the map as providing damage/risk reduction.  (FEMA must either 
assume that the levee continues to provide damage/risk reduction or take action to determine 
the present status of the levee.)

This report addresses the current criteria for evaluating levees and floodwalls under the NFIP, the 
procedures for applying these criteria to the above situations, and the impact these actions may have 
on the local community, Map Mod, and the NFIP.  The report also recommends actions to be taken 
to revise current criteria and procedures.
 


2.	The Role of Levees in the NFIP
2.1.	Mapping of Protected Areas
Mapping of areas “protected” by levees has been a critical issue for the NFIP since it was 
established by the National Flood Insurance Act of 1968.  The Act directed the U.S. Department of 
Housing and Urban Development (HUD) to establish floodplain management criteria and to map the 
Nation’s flood hazards, but did not specify a standard.  HUD contracted with the University of 
Chicago’s Center for Urban Studies to conduct a seminar of experts to recommend floodplain 
management criteria and a mapping standard.  The Chicago Seminar recommended that “the 100-
year flood would be a reasonable level to use in identifying flood-prone areas.”  HUD subsequently 
adopted the 100-year flood as the standard for NFIP flood hazard mapping, floodplain management, 
flood insurance rating, and later for implementation of the mandatory purchase requirement.  
However, the report did not specify how that standard should to be applied to levees.
When the NFIP was established, thousands of individual levees existed across the United States, 
ranging from recent U.S. Army Corps of Engineers (USACE) flood control projects, with known 
levels of damage/risk reduction and well documented engineering, to small agricultural levees built 
by individual farmers.  Most levees lay somewhere in between.  The challenge was to determine 
which of these levees should be recognized as providing protection from the 100-year flood.
2.2.	Roles and Responsibilities
Although this report primarily addresses the process that FEMA uses to determine whether levee 
systems can be credited with providing protection from the 100-year flood, it is important to 
recognize that all levels of government have roles and responsibilities in the design, construction, and 
operation and maintenance of levee systems.  These levels include:
*	Federal levee construction agencies.  Federal agencies such as USACE, the Natural 
Resources Conservation Service (NRCS), and other agencies design and construct levees 
pursuant to authorizations and appropriations from Congress.   These projects usually 
require a local sponsor, which can be a community or a special district.
*	State governments.  States play several roles in levee construction and levee safety.  
Some States directly regulate levee construction, including the establishment of design 
standards and the review and approval of levee engineering.  States may also require 
operation and maintenance plans as a condition of levee approval, conduct levee inspections, 
and require emergency action plans.  States also perform important roles in implementation 
of the NFIP including floodplain management and flood hazard mapping.
*	Local governments.  Local governments, including communities and special districts, can 
design and construct levee systems or act as the local sponsor when a Federal agency 
designs and constructs a levee system.  In both situations, the local government will usually 
assume the responsibility for operation and maintenance of the levee system and for 
emergency planning.  Local governments have a critical role in determining the level of 
damage/risk reduction provided by a levee system since they must fund the design and 
construction of the system or, as the local sponsor, be willing to share in the cost of the 
system with the Federal government.
*	Federal Emergency Management Agency.  FEMA administers the NFIP and, as part of 
that program, conducts flood hazard mapping for the Nation.  As part of the mapping 
program FEMA must determine whether a levee can be credited as providing 100-year 
protection.

2.3.	Levee Design, Certification, and Accreditation
FEMA has established procedures to govern the determination that a levee can be credited as 
providing protection from the 100-year flood.  FEMA’s determination is made for the purposes of 
administering the NFIP’s floodplain management, flood insurance, and mandatory purchase 
requirements, and does not necessarily mean that the levee provides adequate damage/risk 
reduction for a particular community.  Depending on the circumstances, higher levels of damage/risk 
reduction may be warranted.  For purposes of this report, it is important to recognize the differences 
between levee design, levee certification, and levee accreditation.  FEMA procedures include 
consideration of:
*	Levee design.  When designing a levee system, the most critical decision that must be 
made is the design level of damage/risk reduction to be provided by the levee system.  The 
optimal design level of damage/risk reduction for a levee will vary based on a number of 
factors, such as the severity of the risk of flooding to life and property, the critical nature of 
the facilities to protected, the economics of levee construction, and other factors.  FEMA 
has established minimum design criteria for crediting levees for the purposes of 
administration of the NFIP.  FEMA design criteria need to be taken into account during the 
design process, but should not be the primary factor in determining the design level of 
damage/risk reduction for the levee system.
*	Levee certification.  A registered professional engineer must certify that a levee system 
complies with the structural requirements of 44 CFR 65.10.  Certification is further defined 
in 44 CFR 65.2.  As an alternative, a Federal agency with responsibility for levee design may 
certify that the levee has been adequately designed and constructed to provide protection 
against the base flood.  FEMA does not certify levee systems.
*	Levee accreditation.  Accreditation is the process of determining whether a levee can be 
credited as providing protection from the 100-year flood.  FEMA bases its decision on 
information submitted by the community or another party seeking recognition of the levee 
and, in particular, places reliance on the certification by a registered professional engineer or 
a Federal agency with responsibility for levee design.

2.4.	The Early Days
When the NFIP was established, little guidance was available to deal with the inclusion of existing 
flood damage/risk reduction systems in the program.  A 1982 report by the National Academy of 
Science’s National Research Council (NRC) offered a succinct history of how levees were credited 
during the initial years of the program:
“For the conduct of this mapping program (the initial FHBMs), FEMA did not provide guidance for 
evaluation and acceptance of local flood protection works, such as levees, as sufficient for removal of 
special flood hazard area designations.  The assessment of a particular protection work was left to the 
judgment of the agency or consultant who produced the map.  In most instances, because of time and 
cost constraints, levees with crown elevations exceeding estimated 100-year flood levels were credited 
with providing protection against the 100-year flood.  Little or no consideration was given to freeboard 
requirements, structural stability, or maintenance.
As a result of the Flood Disaster Protection Act of 1973, the mapping to define flood risk zones, called 
flood insurance studies, was also accelerated.  The lack of a specific policy for treating leveed areas 
carried over into the rate mapping program, and the study contractor’s evaluations were made primarily 
on the basis of field reconnaissance and a comparison between levee crown elevations and computed 
100-year flood levels.”
In 1975, following the initiation of a significant number of rate studies, the need for a formal levee policy 
became more apparent.  The Federal Insurance Administration (FIA) began receiving requests from study 
contractors for guidance on evaluation of levees.  Land developers began requesting that FIA provide 
standards that levees must meet so that “protected” areas could avoid the special flood hazard 
designation.  Various groups were constructing 100-year design levees for the sole purpose of removing 
property from the floodplain management, lender notification, and insurance purchase requirements under 
the NFIP.”

Throughout this early period, decisions were made on whether to credit thousands of levees.  
Because there were no levee standards and crediting of a levee was left largely to the judgment of 
the study contractor, many levees were credited as providing flood protection even though they 
would not meet the current NFIP levee standards as stated in 44 CFR 65.10.  During subsequent 
remappings, many of these levees were re-evaluated and either credited as providing flood 
protection or not credited.  An unknown number are currently shown as providing flood protection, 
but do not meet the standards of 44 CFR 65.10 or have never been evaluated against those 
standards.  Some of these areas have been restudied, but the initial crediting of the levee was not 
reevaluated, and the FIRM continues to show the levee as providing 100-year protection.
2.5.	The Brooks Amendment and the Establishment of A99 
Zones 
Once the Flood Disaster Protection Act of 1973 was passed, establishing the mandatory flood 
insurance purchase requirement, the FIA faced increased pressure to recognize levees as providing 
flood protection.  The crediting of levees now determined whether or not property owners would 
have to purchase flood insurance in order to obtain a mortgage from a federally insured or regulated 
lender or other Federal financial assistance.  The U.S. Congress passed the Brooks Amendment in 
1974, leading to the establishment of A99 zones.  Under the Brooks Amendment, any community 
that has made adequate progress on the construction of a flood protection project that will afford 
protection from the 100-year flood is eligible for flood insurance at rates no greater than the rate that 
could be charged had the project been completed (A99 rates are currently the same as Zone B, C, 
and X rates).  Adequate progress was defined as: 
“(1) 100 percent of the project cost of the system has been authorized, (2) at least 60 percent of the cost of 
the system has been appropriated, (3) at least 50 percent of the cost of the system has been expended, 
and (4) the system is at least 50 percent completed.”
FIA’s implementing regulations at 44 CFR 61.12 further limit A99 zones to flood protection systems 
involving Federal funds.  Apparently, this is based on the amendment’s language about the cost of 
the project being authorized and appropriated and the belief that federally funded flood damage/risk 
reduction systems were more likely to be completed than those funded by local 
governments or the private sector.  Because A99 zones continue to be Special Flood Hazard 
Areas (SFHAs), the mandatory flood insurance purchase requirement remains in effect.  Buildings 
in A99 zones do not have to be elevated or floodproofed to the BFE, but they do have to meet other 
floodplain management requirements.
The Brooks Amendment is important for two reasons.  First, it codified the 100-year flood as the 
standard for the recognition of levees.  Second, it set a precedent for special treatment of areas 
protected by levees in a levee system that no longer provides protection from the 100-year flood.
2.6.	FEMA’s 1981 Interim Levee Policy and Issuance of 
44 CFR 65.10
During the late 1970s, FIA’s policy toward crediting levees evolved as more Flood Insurance 
Studies (FIS) were conducted, and decisions had to be made on crediting individual levee systems.  
This culminated in the issuance of The FEMA Interim Levee Policy on February 10, 1981.  This 
policy included many of the same elements found in 44 CFR 65.10.  Key elements of the Interim 
Levee Policy included the following:
*	Privately owned, operated, or maintained levee systems would not be recognized unless local 
ordinances or State statutes mandated operation and maintenance.
*	A minimum of 3 feet of freeboard was established, with provisions for exceptions for lower 
freeboard where the applicant demonstrated a lower level of uncertainty.
*	The study contractor was required to inspect and evaluate the levee or obtain certification 
from a Federal or State agency or registered professional engineer.
*	FIA would not recognize levees that require human intervention for the purpose of raising 
the levee’s design level during a flood.  Any closure structures must be designed to be an 
integral part of the system.
*	Protected areas were to be shown as Zone B (now Zone X (shaded)) on the FIRM and 
internal drainage areas mapped as appropriate.  Floodway boundaries were to be at the 
landward toe of the levee.
*	The USACE manual for Design and Construction of Levees (EM 1110-2-1913) was to be 
used in conjunction with the policy.
*	Standards relative to seepage, surface erosion, and settlement were defined.

Guidelines for Operation and Maintenance of Levees, Floodwalls, and Interior Drainage Facilities 
also were developed at this time.
FIA was advised in the early 1980s by FEMA’s Office of General Council that, for legal reasons, 
the levee policy needed to be promulgated by regulation.  FEMA issued a final rule on 
August 25, 1986 adding 44 CFR 65.10 to the NFIP regulations.
2.7.	National Research Council Report
In addition to issuing the Interim Levee Policy, FEMA contracted with the National Academy of 
Science’s NRC to make recommendations for a comprehensive levee policy for use in administering 
floodplain management, insurance, and risk mapping aspects of the NFIP.
A committee of experts assembled and issued a report titled A Levee Policy for the National 
Flood Insurance Program at the end of 1982.  FEMA’s request to NRC cited numerous concerns 
with levees:
*	Levee overtopping or failure is involved in approximately one-third of all flood disasters.
*	As a design standard, the 100-year flood is generally too low for densely populated areas.
*	Most earthen levees with their crowns at the computed 100-year flood level will not provide 
protection against the true 1-percent-annual-chance flood due to uncertainties in determining 
flood elevations, changing hydrologic conditions, and the possibility of failure before they are 
overtopped.
*	The degree of protection from a 100-year design levee is less than that obtained by elevating 
individual buildings to above that elevation due to catastrophic damages that would occur as 
a result of overtopping or failure.
*	Crediting a levee system as providing 100-year protection removes floodplain management 
and insurance purchase requirements and may violate the spirit of the NFIP by encouraging 
development in damage-prone areas.

The NRC report recommends criteria for recognizing levees, many of which are consistent with 
current provisions of 44 CFR 65.10.  The report also includes recommendations that have not been 
incorporated into the NFIP or of particular interest to this study.  These recommendations include:
*	Existing levees that provide at least 25-year protection and meet design criteria should be 
recognized for the purpose of reducing flood insurance rates.
*	FEMA should monitor watershed and channel changes where hydrologic risk is increasing 
and respond to significant changes with restudies and map revisions.
*	FEMA should inventory all levees previously credited as providing 100-year protection, set 
priorities, and schedule the communities for restudies to re-evaluate the levees.
*	The levee owner must formally adopt a specific operations and maintenance plan if the levee 
is to be credited and continue to be credited.  The plan should provide for periodic 
inspections by a registered professional engineer.
*	FEMA should require the purchase of flood insurance for all buildings behind levees that 
provide less than 500-year protection.
*	Local officials should periodically notify owners, tenants, and lenders behind levees of 
potential risk.
*	Local officials should prepare a warning and evacuation plan for levee-protected areas.
*	FEMA should contract to develop a list of key factors to evaluate the physical condition of 
the levee and guidance on using those factors to estimate geotechnical risk.
*	All levees, dikes, or floodwalls should be clearly labeled as such on the FIRM.  Areas 
protected by 100-year levees should be delineated on FIRMs and Flood Hazard Boundary 
Maps (FHBMs).
*	A series of recommendations are made about a very detailed set of zone designations for 
levees providing various levels of protection.  The concern appears to be establishing 
actuarial insurance rates that accurately reflect risk behind levees.

Several of these recommendations are at least partially addressed in 44 CFR 65.10; others are not.
2.8.	Establishment of Flood Control Restoration Zones 
(Zone AR )
Floods along the American River in Sacramento, California, and the Los Angeles River in Los 
Angeles County during the 1980s led USACE to reevaluate the hydrology of the two river systems 
and the level of damage/risk reduction provided by both flood damage/risk reduction systems.  
USACE concluded that the flood damage/risk reduction systems provided less than 100-year 
protection and notified FEMA.  Normally, the next step would have been for FEMA to restudy the 
rivers and issue new FIRMs showing the areas behind the levees as AE zones.  Decertification of 
these flood damage/risk reduction systems would have directly affected hundreds of thousands of 
people in the Los Angeles and Sacramento areas.   In Los Angeles County alone, 14 Congressional 
Districts were directly impacted.
The severity of these impacts (thousands of property owners would have to purchase flood 
insurance) led the California Congressional delegation to propose and Congress to pass certain 
provisions in the Housing and Community Development Act of 1992, which amended Section 1307 
of the National Flood Insurance Act of 1968 to establish AR zones  This new zone type was 
intended to provide the affected communities with time to restore their flood damage/risk reduction 
systems so that they would meet the requirements of 44 CFR 65.10 without the areas being 
designated as AE zones.  FEMA worked with the California delegation to develop language that 
could be implemented and provided some relief to property owners and the affected communities 
while the levees were being restored.  Key provisions of the Act include:
*	The project must have been previously credited as providing 100-year frequency flood 
protection but no longer does so.
*	A Federal agency in consultation with the local sponsor must deem the system restorable.
*	A minimum level of flood protection must still be provided.
*	Restoration must occur within a designated time period in accordance with a progress plan 
negotiated between FEMA and the community.
*	While the area was designated Zone AR, flood insurances rates could not exceed those 
applied in Zone X.
*	AR zones were to be SFHAs and the mandatory flood insurance purchase requirement 
would apply.
*	Floodplain management criteria would not apply to improvements to existing structures and 
elevation requirements for new construction could not exceed 3 feet above grade in 
developed areas.

FEMA adopted implementing regulations that became effective on October 25, 1994.  These 
regulations limited AR zones to levees constructed using Federal funds.  The Act itself only requires 
that a Federal agency in consultation with the project sponsor deem the system restorable.


The supplemental information to FEMA’s Final Interim Rules includes the following rationale for this 
further limitation:
“FEMA concludes that a lack of Federal involvement in the restoration process would introduce too great 
an uncertainty that the restoration project would be completed in a timely manner.”
In both areas, the levee systems were restored to provide 100-year flood protection.  The areas are 
now shown as shaded X zones.  Although several communities have expressed interest in Zone AR 
designation in the years since, no additional AR zones have been designated.  This may change as 
Map Mod proceeds.
The problems with the American River levee system brought to the forefront the issue of residual 
risk behind levees.  Of greatest concern was the Natomas Basin, a 55,000-acre, partially developed 
area immediately north of downtown Sacramento.  The concern was that, if the levee system was 
restored to provide 100-year protection, the area would be fully developed and an estimated $15 
billion of dollars of additional development would be at risk if the levee system was overtopped or 
failed.  The NRC assembled a committee to evaluate alternatives to provide flood damage/risk 
reduction along the American River.  Its report, Flood Risk Management and the American River 
Basin; An Evaluation, published by the National Academy of Sciences in 1995, discussed in detail 
the issue of residual risk and recommended in part that local governments work with FEMA to 
require that landowners purchase actuarially sound flood insurance to address the residual risk 
behind levees.
2.9.	Midwest Flood of 1993
In 1993, the Midwest Flood again brought issues related to levees to the forefront.  The flood 
approached or exceeded the 100-year threshold on most major rivers and resulted in overtopping or 
failure of large numbers of levees, most of them agricultural levees that provided various levels of 
damage/risk reduction.  Most of the levee issues related to the advisability of repairing agricultural 
levees and to the operation of the PL 84-99 levee repair program by USACE.
Although only a few of the levee systems that were credited as providing 100-year protection were 
overtopped or failed, several levee systems protecting major urban areas, including parts of the 
City of St. Louis, were threatened.  Had the flood been somewhat larger, these levee systems could 
also have been overtopped or failed.  The single most costly levee failure during the Midwest Flood 
was the Monarch-Chesterfield Levee at Chesterfield, Missouri.  This levee was an agricultural 
levee that had been upgraded during the early 1980s and was credited by FEMA as providing 
protection from the 100-year flood.  Once the levee was credited, industrial and commercial 
development occurred.  When floodwaters threatened the levee, most businesses bought flood 
insurance.  When the levee failed, more than $13 million in claims were paid, 5 percent of the total 
claims for the Midwest Flood.  This levee has since been rebuilt and upgraded to provide 500-year 
flood protection.
In the aftermath of the Midwest Flood, the Administration established the Interagency Floodplain 
Management Review Committee to review the causes and consequences of the flood and make 
recommendations for improvements to Federal floodplain management programs and policies.


Its report, Sharing the Challenge: Floodplain Management into the 21st Century (Interagency 
Floodplain Management Review Committee, June 1994, made the following recommendations 
regarding levees protecting urban development:
*	Reduce the vulnerability of population centers to damage from the standard project flood 
discharge.
*	Require actuarial-based flood insurance behind all levees that provide protection less than the 
standard project flood.
*	Establish USACE as the principal federal levee construction agency.

The Midwest Flood also resulted in a reevaluation of the 100-year flood discharges and the flow 
lines along the Mississippi River.  Incorporating the new flow lines into Map Mod will require 
reevaluation of many of the levee systems along the Mississippi River that are currently credited as 
providing flood protection.
2.10.	Hurricane Katrina
Hurricane Katrina hit the New Orleans area on August 29, 2005, as a Category 3 storm.  It first 
appeared that most levees protecting the City of New Orleans itself had not been overtopped, 
although levees in St. Bernard Parish to the south had been inundated by storm surge, as shown in 
figure 2-1.  One day later, it became apparent that a number of floodwalls along canals in the city 
had failed and that the city was slowly filling up with water.  What initially appeared to be a large 
flood event quickly became the most costly natural disaster in the history of the United States.  New 
Orleans not only faces the challenge of protecting itself against external flood threats, but must also 
provide for the major infrastructure necessary to pump rain waters from inside the levees.  Many 
New Orleans residents are subject to mandatory insurance purchase because they reside in a SFHA 
created because the city cannot pump out storm waters.
 
Figure 2-1.  New Orleans was inundated by floodwaters following Hurricane Katrina.
As of the date this report was written, floodwall failure mechanisms, pumping system performance, 
and the level of damage/risk reduction actually provided by the pre-hurricane levee systems all are 
still being debated.
New Orleans and the surrounding areas have historically been one of the most flood-prone areas of 
the nation due to internal drainage problems.  Much of the area is below sea level and major 
infrastructure, including canal systems and pumping stations, are required to collect storm water and 
pump it out over the levees.   Many areas are designated as SFHAs due to internal drainage and, as 
a result, significant numbers of property owners fortunately had flood insurance at the time of the 
event.  After Hurricane Katrina, this internal drainage problem created an added dimension to the 
flooding by requiring pumping from areas below sea level, which took weeks to complete.
USACE initially intended to restore the level of protection provided by the levee systems to their 
pre-Katrina level (protection from a Category 3 storm) by the start of the 2006 hurricane season.  
Widespread discussion continues on the subject of raising the city’s level of protection (i.e., 
protecting it from a Category 5 hurricane) to restore public confidence in the New Orleans levee 
systems and assist in economic recovery.  However, the need to correct structural problems with 
the levees and floodwalls and the need to raise or reinforce the levees in many areas apparently 
could make achieving even Category 3 protection difficult and costly.  Additional storm frequency 
information and flood elevations developed after Hurricane Katrina have resulted in further 
re-evaluation of the level of protection provided by the levee systems.  USACE and FEMA jointly 
announced that 100-year flood protection will not be achieved until 2010 for most areas.
In the interim, FEMA has issued Advisory Base Flood Elevations and recommended requirements 
within the levee systems.  The FEMA guidance states that the requirements are similar to those in 
Zone AR.  FEMA recommends that new and substantially improved buildings are to be elevated to 
the current BFE or 3 feet above existing ground elevation, whichever is higher.  Presumably, the 
area could then become Zone AR when a new FIRM is issued.  If the communities do not adopt 
this requirement, BFEs would be “without levee” BFEs, once the new FIRMS are issued.  The issue 
of providing a higher level of damage/risk reduction will not be resolved until completion of a 
USACE technical report analyzing higher levels of damage/risk reduction. 
Many lessons were learned as a result of Hurricane Katrina, including the following:
*	Failure of a levee system in a major urban area can result in a catastrophe with billions of 
dollars of damage and significant loss of life.
*	Levees and floodwalls can fail during flood events of lesser magnitude than the design flood.  
(Prior to Katrina, the chance of failure of a major flood control project was largely 
discounted and the major threat was though to be overtopping by a flood larger than the 
design flood.)
*	There is renewed debate over the appropriate level of flood damage/risk reduction to provide 
in a major urban area.
*	The public should now be more aware of the consequences of levee overtopping or failure.
*	The politics of levees may have shifted, at least for the immediate future, in the direction of 
greater caution and higher levels of damage/risk reduction.

It remains to be seen whether Hurricane Katrina will result in long-term changes to national levee 
policy.


3.	FEMA Requirements for Mapping Levees: 
Challenges, Opportunities, and Options
This section examines the current FEMA requirements, policies, and guidelines that provide the 
framework for the inclusion of levees on NFIP maps and their recognition by FEMA.  It also 
identifies the most important challenges and issues with the current requirements and policies facing 
FEMA, as identified by the Interagency Levee Policy Review Committee, and concludes with 
recommended changes to the FEMA mapping requirements.
3.1.	Current FEMA Requirements for Mapping Levees
FEMA requirements for mapping levees include NFIP regulations, FEMA’s Guidelines and 
Specifications for Flood Hazard Mapping Partners (Guidelines and Specifications), and 
FEMA procedure memoranda.
3.1.1.	Regulatory Requirements
Regulatory requirements for the NFIP are contained in 44 CFR Chapter 1, Parts 59-77.  Specific 
regulatory requirements governing the treatment of levees in the NFIP are described below.
3.1.1.1	44 CFR 59.1, Definitions
This subsection provides the regulatory definitions of levee, levee system, and freeboard.
A levee is defined as “…a manmade structure, usually an earthen embankment, designed and 
constructed in accordance with sound engineering practices to contain, control, or divert the flow of 
water so as to provide protection from temporary flooding.” 
A levee system is defined as “…a flood protection system which consists of a levee, or levees, and 
associated structures, such as closure and drainage devices, which are constructed and operated in 
accordance with sound engineering practices.”
Freeboard means “… a factor of safety usually expressed in feet above a flood level for the purpose 
of floodplain management.  Freeboard tends to compensate for the many unknown factors that 
could contribute to flood heights greater than the height calculated for a selected-size flood and 
floodway conditions, such as wave action, bridge openings, and the hydrological effect of 
urbanization of the watershed.” 
3.1.1.2	44 CFR 61.12, Rates Based on a Flood Protection System Involving Federal 
Funds
As discussed in Section 2.c of this report, 44 CFR 61.12 (commonly referred to as the “Brooks 
Amendment”) provides for the mapping of flood damage/risk reduction systems, such as levees and 
levee systems, undergoing federally funded restoration where adequate progress has been made 
toward achievement of 100-year flood protection.  44 CFR 61.12 provides the specific criteria for 
determining whether adequate progress has been made.  These criteria include:
*	100 percent of total cost authorized
*	At least 60 percent of total cost appropriated
*	At least 50 percent of total cost expended
*	All critical features under construction and at least 50 percent complete
*	Community has not been responsible for any delay in project completion

Areas protected by levees that meet the criteria of 44 CFR 61.12 are mapped so that the protected 
area is designated as Zone A99 on the FIRM, with no flood depths or BFEs specified.  The 
mandatory flood insurance purchase requirement applies in Zone A99, but the rates are based on the 
flood insurance zone that will apply after the levee system is complete (typically Zone B, C, or X).
3.1.1.3	44 CFR 64.3, Flood Insurance Maps
This section, which does not specifically address levees, provides the regulatory definition of the 
flood insurance zones depicted on flood insurance maps.  Zones B and X (shaded) are defined as 
“area of moderate flood hazards” and purchase of flood insurance is voluntary and at lower rates 
than in Zones A, AE, A1-30, AO, and AH.  On the standard FIRM panel legend, Zone X (shaded) 
is defined as “Areas of 0.2% annual chance flood; areas of 1% annual chance flood with depths 
less than 1 foot or with drainage area less than 1 square mile; and areas protected by levees from 
the 1% annual chance flood.”  Thus, there is no distinction in flood insurance zone designation for 
areas in the 500-year floodplain, areas of the 100-year floodplain with shallow depths and/or small 
drainage areas, and areas protected by levees.
3.1.1.4	44 CFR 65.10, Mapping of Areas Protected by Levee Systems
Provides the data analysis and submission requirements that levee systems must meet, and continue 
to meet, to be recognized on FIRMs as providing protection from the 100-year flood.  The criteria 
include design, operation, and maintenance standards.  Design criteria include minimum freeboard 
requirements, closures, embankment protection, embankment and foundation stability, settlement, 
and interior drainage.  Structural requirements must be certified by a registered professional 
engineer and certified “as built” plans must be submitted.  However, in lieu of the structural 
requirements, a Federal agency with responsibility for levee design may certify that a levee has been 
adequately designed and constructed to provide protection against the base flood.
Operation and maintenance plans must be formally adopted and be under the jurisdiction of a 
Federal or state agency, an agency created by Federal of state law, or a community participating in 
the NFIP.
3.1.1.5	44 CFR 65.14, Remapping of Areas for Which Local Flood Protection Systems 
No Longer Provide Base Flood Protection
This section describes the procedures for designation of AR zones for flood damage/risk reduction 
systems, such as levees, that no longer provide 100-year flood protection.  A community may be 
eligible to apply for this designation if the system was constructed using Federal funds, recognized 
previously as providing protection from the base flood on the effective FIRM, and decertified by a 
Federal agency responsible for flood protection design or construction.  The restoration must be 
complete within 10 years from application submittal for restoration projects with Federal funding and 
5 years from application submittal for restoration projects with no Federal funding.  In areas 
designated as Zone AR, mandatory flood insurance purchase requirements apply and the rates have 
been set at the non-SFHA level by administrative order.  To date, this designation has only been 
used in the Los Angeles and Sacramento areas of California.
3.1.2.	FEMA Guidelines and Specifications for Flood Hazard Mapping 
Partners
Guidelines and Specifications Appendix H, Guidance for Mapping Areas Protected by Levee 
Systems, provides guidance to FEMA engineering and mapping contractors and Cooperating 
Technical Partners (CTPs) for mapping of areas protected by levee systems.  Appendix H of the 
Guidelines and Specifications provides steps for contractors and CTPs to evaluate levees when 
performing hydrologic and hydraulic analyses of flooding sources with levees, including the 
following:
*	Determining levee ownership
*	Determining status of all system elements (e.g., credited or unaccredited)
*	Obtaining all available supporting documentation (e.g., as-builts, interior drainage analyses) 
from the system owner, operator, or FEMA repository
*	Obtaining written confirmation of any previous certification
*	Performing/updating hydraulic analyses of 10-percent-, 2-percent-, 1-percent-, and 0.2-
percent-annual chance floods reflecting levee in place
*	Assessing freeboard using “as built” levee profiles or topographic data and the 1-percent-
annual-chance profile
*	Reviewing available operation and maintenance plans to determine compliance with 
44 CFR 65.10

The contractor or CTP then is to prepare a final letter report to the Regional Project Officer 
summarizing the results and conclusion of the levee evaluation.  The Regional Project Officer, in 
consultation with the regional engineers, makes the final decision concerning the credibility of the 
levee system.
Appendix H of the Guidelines and Specifications also provides the procedures for preparing 
floodplain mapping and flood profiles for levee areas.  For levees meeting 44 CFR 65.10, as 
determined by the Regional Project Officer, flood profiles reflect the “with levee” condition.  The 
protected area is designated as Zone X (shaded), and the interior drainage areas are designated as 
100-year floodplain (e.g., Zone AH, AE).  The regulatory floodway is delineated at the landside toe 
of the levee.
For levees not meeting the requirements of 44 CFR 65.10 (as decided by the Regional Project 
Officer), both sides of the levee are shown as 1-percent-annual-chance floodplain (i.e., Zone AE).  
The area on the unprotected (riverward) side of levee is designated based on the “with levee” 
1-percent-annual-chance profile (the top of levee elevation can be used if the “with levee” 
1-percent-annual-chance profile overtops the levee).  The area on the landward side of levee is 
based on the recomputed “without levee” profile.  The line along the levee centerline separates the 
areas of different BFEs on the FIRM.  The flood profile sheets may have up to five profiles:  the 
10-, 2-, and 1-percent-annual-chance profiles for the “with levee” condition for the riverward side of 
levee; and 1- and 0.2-percent-annual-chance profiles for the “without levee” condition for the 
landward side of levee.  The regulatory floodway widths are determined based on the “without 
levee” condition, and two BFEs (riverside and landward side conditions) are included in the 
“Regulatory” column of the Floodway Data Table.  In cases for which levees exist on both sides of 
a stream, evaluation shall consider simultaneous levee failure, failure of only the left side, and failure 
of only the right side.
Lastly, Guidelines and Specifications Appendix H requires mapping contractors and CTPs to 
ensure that levees in/adjacent to floodplains are documented and inventoried in the Web-based 
FEMA Levee Inventory System (FLIS).
3.1.3.	FEMA Procedure Memoranda
FEMA has issued three procedure memoranda related to mapping of levees for the NFIP.  An 
overview of each is provided below.
3.1.3.1	Procedure Memorandum 30 - FEMA Levee Inventory System 
(December 23, 2002)
This memorandum established a process for maintaining the FLIS and provided protocol for data 
entry to electronically store the system data.  The process provided for the FEMA Mapping 
Coordination Contractors (MCCs) to perform levee inventories for FEMA-contracted mapping 
projects and community-initiated map revisions.  The inventories are to be performed by checking, 
validating, and updating as appropriate, information in the FLIS, or by adding new records for levees 
not already entered in the FLIS.
3.1.3.2	Procedure Memorandum 32 - Levee Review Protocol (June 4, 2003)
This memorandum established a tiered system of review protocol for the evaluation of levees along 
flooding sources that are not part of a specific study or restudy.  Inherent to this review protocol is a 
requirement that the MCC keep a watchful eye for levees that were not properly identified, 
classified, and/or inventoried in past map actions.  For credited levees along non-studied/restudied 
flooding sources, the protocol calls for a quick visual assessment for obvious anomalies in the 
mapping.  Obvious anomalies for levees shown as providing protection from the 100-year flood 
include the following:
*	No indication in the FIS report that the levee has minimum freeboard
*	No note on the effective NFIP map in the protected area warning of residual flood risks
*	Floodway (when present) not delineated at the inside toe of the levee

Performing this visual inspection for levees outside the primary scope of the map project enables the 
revision to proceed while a back-check is conducted to validate 44 CFR 65.10 criteria.  If problems 
are determined during the back-check, those problems may be addressed separately.  Depending on 
the gravity of the problems, the map action may either be halted (in extreme cases) or addressed in 
a follow-up action.
3.1.3.3	Procedure Memorandum 34 - Interim Guidance for Studies Including Levees 
(August 22, 2005)
This memorandum provides interim guidance on how mapping contractors and CTPs should treat 
levees to minimize delays in near-term mapping projects while a long-term levee policy is being 
established.  A key part of this interim guidance is that for all levees along non-restudied flooding 
sources, full compliance with 44 CFR 65.10 must be documented.  (As described previously, 
Appendix H of the Guidelines and Specifications only calls for levee assessments when new or 
updated H&H analyses are being performed).  This has a profound impact because many of the 
mapping projects initiated during the early years of Map Mod are “digital conversions” in which the 
community-based, paper FIRMs are upgraded to full countywide Digital Flood Insurance Rate Maps 
(DFIRMs).  Although these countywide DFIRM conversions frequently include redelineation of 
floodplain boundaries on new topographic data, their scope typically includes new or updated H&H 
analyses for very few, if any, flooding sources.
The memorandum establishes that FEMA will not be conducting detailed examinations of levees to 
determine how a structure or system will perform in a flood event.  Rather, as required in 
44 CFR 65.10(a), the memorandum reaffirms that it is the responsibility of the community or party 
seeking recognition of a levee system to provide the data specified in 44 CFR 65.10.  A deadline for 
submission of the data to FEMA will be established and, if the required data and documentation are 
not provided by the deadline, the levee cannot be recognized as providing protection from the base 
flood as part of the mapping project.
3.2.	Challenges and Issues with Current Requirements and 
Policies
After careful consideration and evaluation of the FEMA requirements for mapping levees under the 
NFIP, the Committee identified the following challenges and issues:
*	Many levees shown on current NFIP maps as providing protection from the 100-year flood 
have never been evaluated against the criteria of 44 CFR 65.10 (see discussion of 
“grandfathered” levees in Section 2).  As Map Mod is implemented, Procedure 
Memorandum 34 will require that these “grandfathered” levees be evaluated against 
44 CFR 65.10 requirements.  For levees that are found not to meet 44 CFR 65.10, the areas 
behind the levees will be identified as SFHAs.  The impacts on the community of such an 
action will be significant.
*	The protection afforded by many certified levees decays over time due to various factors, 
such as changed hydrology or channel characteristics, erosion or deterioration of the 
embankment due to rodents or tree growth , general lack of proper maintenance, subsidence, 
or partial levee failures.  However, there is no mechanism in place to regularly verify 
continuing accreditation of levees against 44 CFR 65.10.  Procedure Memorandum 34 
establishes that all currently credited levees will be checked against the 44 CFR 65.10 
criteria as Map Mod is implemented.  When combined with reviewing “grandfathered” 
levees as described above, this should bring the accreditation status for all levees up to date 
in the program.  There is still no mechanism in place to periodically revisit the levee 
accreditation status in subsequent years unless a FIRM update is initiated for the community 
for other reasons (and then only if the requirements of Procedure Memorandum 34 are 
followed by the contractor or CTP).
*	FEMA does not certify levees, but rather relies on certification provided by Federal agencies 
or State, local, or other parties seeking accreditation on NFIP maps.  In implementing 
Procedure Memorandum 34, because levees were often “grandfathered” or certification of 
44 CFR 65.10 criteria cannot be found, FEMA is reiterating that it is the responsibility of 
communities to provide the necessary certification.  Frequently, communities do not have the 
requisite resources or technical expertise to properly evaluate the levees against the 
44 CFR 65.10 requirements and will have to hire engineering firms to do this work.  The 
amount of time needed to accomplish this recertification could impact schedules, delaying 
issuance of preliminary and effective DFIRMs and slowing completion of Map Mod.
*	As Procedure Memorandum 34 is implemented, many levees ultimately will not meet the 
criteria of 44 CFR 65.10 and will have to be shown as “failed” on FIRMs.  The performance 
of detailed levee failure analysis as required by Appendix H of the Guidelines and 
Specifications will be costly, particularly for countywide DFIRM conversion projects and in 
counties and communities with large numbers of levees.  In some instances, the detailed 
restudy and assessment of levees may cost nearly as much, if not more, than the DFIRM 
conversion project itself.  This may significantly delay finalizing modernized maps and/or 
severely limit the number of counties and communities that can be mapped in any given year.  
These problems must be balanced against the threat to safety of not performing adequate 
analyses.
*	The regulatory requirements of 44 CFR 65.10 lack adequate specificity for minimum 
operation and maintenance standards.  In addition, although the maintenance requirements 
require that maintenance plan must ensure that levee stability, height, and overall integrity are 
maintained, there is no specific requirement for ensuring that the flood-carrying capacity of 
the main river channel is maintained.  In some instances, the main river channel has lost 
flood-carrying capacity adjacent to a levee due to silt and sediment deposits in the channel.  
Further, encroachments into levees can range from a sprinkler pipe buried in the face of an 
urban levee to a six foot diameter sanitary sewer pipe placed under the levee.  In California, 
the Department of Water Resources (DWR) has issued permits for more than 18,000 
encroachments in the Sacramento and San Joaquin Levee System alone.  These 
encroachments can hinder operations and maintenance and/or the ability to flood fight or 
even compromise levee integrity.  Maintenance programs must include control of new 
encroachments and correction of problems with existing encroachments prior to levee 
certification.
*	Risks in areas behind certified levees are not adequately communicated to map users.  For 
example, areas protected by levees certified to meet 44 CFR 65.10 criteria are given the 
same flood insurance zone designation (Zone X (shaded)) as the 500-year floodplain and the 
100-year floodplain with depths less than 1 foot or drainage areas less than 1 square mile.  In 
addition, the standard levee note that is used on FIRMs is “This area protected from the 1-
percent-annual-chance (100-year) flood by levee, dike, or other structures subject to possible 
failure or overtopping during floods.”  The use of the word “protected” in this note may give 
an undue sense of security to map users.  At a minimum, maps should indicate that 
protection is designed only for specific flood events.
*	Current requirements treat levees in a binary manner—either they meet 44 CFR 65.10 or 
they do not.  Therefore, residual risk is greatly under-represented, and differences in risk that 
may exist to those behind certified levees are disregarded.  In addition, no distinction 
between graceful versus chaotic capacity exceedance exists in the way levees are mapped, 
and there is no identification of the most highly hazardous areas immediately behind/along 
levees in the event of levee failure.
*	Interior drainage due to rainfall ponding behind levees is often under-represented on many 
FIRMs.  Regulations and Guidelines and Specifications lack specificity in acceptable 
techniques for analyzing and mapping interior drainage.  For many levees, little or no analysis 
of interior drainage exists.  The issue of interior drainage, as a contributing factor to residual 
risk, is largely unstudied.
*	For levees determined to meet 44 CFR 65.10, Appendix H of the Guidelines and 
Specifications requires only analyzing the “with levee” hydraulic profile.  Thus, the area 
subject to inundation in the event of levee failure can not be identified without additional 
study.
*	The regulations do not require submission of “for the record” data for certifications by a 
Federal agency responsible for levee design.  Thus, in later years, if FEMA needs to revisit 
the 44 CFR 65.10 certification of a particular levee, it may only have on file a letter of 
certification from the Federal agency, rather than the backup data upon which the Federal 
agency based its certification.  FEMA is encountering precisely this situation now in 
implementing Procedure Memorandum 34.
*	The regulations and Guidelines and Specifications Appendix H lack clarity in the 
treatment of roads, railroads, and other embankments (natural or manmade) that may 
function as levees, leading to confusion by contractors and CTPs and may lead to 
erroneously mapping the areas as “de facto” levees.  Further, map revision requesters 
sometimes attempt to make revision requests under 44 CFR 65.10 based on railroads, 
highways, and other embankments not designed or intended for flood damage/risk reduction.

 
Figure 3-1.  Residual Risk.  Illustration (A) shows the situation when the water level in the 
river is below the BFE.  The levee protects Home 1 up to the 100-year level.  Illustration (B) 
shows the situation when the water reaches the 105-year flood level and overtops the levee.  
Home 1 is submerged and Home 2 is subjected to minimal damage.



3.3.	Conclusions
Based on its review of current mapping standards and requirements, the committee concludes that:
*	Levees only reduce the risk to individuals and structures behind them.  They do not eliminate 
the risk and, in many cases, can create significant and potentially catastrophic residual risk 
that may increase as conditions in the region change.  Levees should be considered as flood 
risk reduction structures, as opposed to flood protection structures, and treated accordingly. 
A structure elevated to the 100-year base flood elevation faces significantly less risk that a 
structure behind a levee designed to withstand the 100-year flood.
*	Current regulations and guidance for recognition and mapping of levees in the NFIP are not 
adequate for making the initial determination that the levees meet minimum design, operation 
and maintenance standards.  The regulations and guidance do not provide adequate oversight 
of levees’ continued conformance with the NFIP criteria.  Therefore, they may permit 
inclusion and/or retention in the program of levees that do not provide the required level of 
protection.
*	Levees should be certified and accredited as systems that include not only levees and 
floodwalls but also the pumps, interior drainage systems, closures, penetrations and 
transitions that provide for systems integrity.

3.4.	Recommended Changes to FEMA Levee Mapping 
Requirements (and Attendant Levee Certification)
The committee recommends that: 
*	FEMA define a new flood insurance zone (Zone XL) for areas behind levees meeting 
requirements for inclusion in the NFIP and, in coordination with other agencies, identify the 
level of risk to those behind these levees.  Zone XL would include those areas behind the 
levee subject to inundation under the 100-year flood in the “without levee” condition.  The 
area between the 100- and 500-year lines would be shown as a shaded Zone X.  Levees 
would also be identified under a scientifically based levee risk classification system 
(e.g., high, medium, or low) that would be based on factors including potential depth of 
flooding in the event of failure or overtopping; type and density of development in protected 
areas behind the levee, and steps taken to ensure that levee failure does not occur during 
levee capacity exceedance (overtopping), warning times, and the number and types of 
egress so that people who may be inundated may move out of harm’s way.  This levee risk 
classification would be designated on the FIRM and in the FIS report.
*	FEMA require levee sponsors to:
?	Conduct annual inspections of the levee systems
?	Submit to FEMA biennially the results of the annual inspections, levee system operation 
and maintenance records, and an assessment of the levee system during any flood 
events that occurred within the reporting period
?	Submit to FEMA every 10 years a report, prepared by a registered professional 
engineer or Federal agency responsible for levee design, that recertifies the engineering 
and geotechnical conditions of the levee system.
*	FEMA should also revise its regulatory and administrative documents as indicated in the 
following paragraphs.

3.4.1.	Regulatory Changes
44 CFR 59.1 Definitions
*	Modify the definition of levee to specifically exclude embankments, such as roads, railroads, 
and natural high ground that were not engineered to provide damage/risk reduction from 
flooding.

44 CFR 64.3 Flood Insurance Maps
*	Define a new flood insurance zone (Zone XL) for areas behind a levee meeting 
44 CFR 65.10 requirements.  This will more clearly distinguish areas behind credited levees 
from the 0.2 percent annual chance floodplain and the 1-percent-annual-chance floodplain 
with depths less than 1 foot and/or drainage areas less than 1 square mile.

44 CFR 65.10 Mapping of Areas Protected by Levee Systems
*	Modify section to specifically exclude application of 44 CFR 65.10 for embankments, such 
as roads, railroads, and natural high-ground that were not engineered to provide protection 
from flooding to revise the FIRMs to remove the SFHA behind the embankment [65.10(a)].
*	Add a requirement for the community or other party seeking accreditation to notify property 
owners in the area behind levee to be removed from the SFHA as a condition of levee being 
accredited under 44 CFR 65.10.  Each individual property owner should be notified in 
writing, clearly explaining the residual risks for levee overtopping and interior drainage, the 
potential for levee failure, and information on how to purchase flood insurance at reduced 
rates.  FEMA should prepare a template notification letter for use by the community or levee 
owner.  Communities could send a notice to property owners every year with their tax bills, 
as some already do.
*	As noted above, add a sub-section requiring the community or other levee owner to 
proactively maintain 44 CFR  65.10 certification, rather than allowing accreditation to remain 
in effect in perpetuity or until the FIRM is revised for other reasons.  As a condition of 
maintaining 44 CFR  65.10 certification for an accredited levee, operation and maintenance 
records, as well as a written assessment of the levee systems performance in any flood 
events that have occurred, should be submitted to FEMA every 2 years.  The engineering 
and geotechnical aspects of the levee should be recertified and submitted to FEMA every 10 
years by a registered professional engineer or Federal agency responsible for levee design.  
If the required data and documentation are not submitted (or submitted but determined by 
FEMA review to no longer meet 44 CFR 65.10 requirements), the levee will be decertified 
and the FIRMs updated to show that the levee no longer provides protection from the 1-
percent-annual-chance flood.  The ongoing conversion of the FIRM inventory to DFIRM 
format by FEMA and the ongoing database of flood damage reduction projects by USACE 
will ultimately provide the GIS platform needed to track and manage the levee 
recertifications.
*	Expand the requirements for maintenance plans to specifically include requirements for 
ensuring that the flood carrying capacity of the main river channel is maintained, thereby 
preserving the required level of protection and ensuring that encroachments are controlled 
and do not affect the integrity of the levee or the ability of its owner to maintain the levee 
and flood fight.  As mentioned previously, there have been some instances in which the main 
river channel has lost flood-carrying capacity adjacent to a levee due to siltation in the 
channel, thereby reducing the levees ability to pass the 100-year flood. Levees should not be 
considered to be properly maintained unless a plan is in effect and working to control 
encroachments.  In addition, FEMA should require the preparation, as part of operation and 
maintenance plans, of emergency action plans for those levees where failure would cause 
catastrophic losses. [65.10(d)].
*	Reference USACE Engineer Manual EM 1110-2-1413, “Engineering and Design, 
Hydrologic Analysis of Interior Areas” as the acceptable/preferred methodology for interior 
drainage analysis.  [65.10(b) (6].
*	Reference the USACE “Levee Owners Manual for Non-Federal Flood Control Works” as 
required for operation, maintenance, and inspection guidance and procedures for non-Federal 
levees and floodwalls.  [65.10(c) and 65.10(d)].
*	Require submission to FEMA of all data, analyses, and documentation used by a Federal 
agency to certify levees and floodwalls for compliance with 44 CFR 65.10.  Although the 
Committee does not recommend that FEMA perform detailed review of the data or the 
certification by another Federal agency, FEMA should maintain copies of the data in the 
backup data for the community’s FIS and DFIRM.  [65.10(e)].

3.4.2.	Guidelines and Specifications for Flood Hazard Mapping Partners
*	Expand Appendix H of the Guidelines and Specifications to cover the evaluation and 
treatment of levees along non-restudied flooding sources following the Procedure 
Memorandum 34 process.
*	Modify the analysis process in Appendix H to more clearly indicate the requirement for 
analysis of the “without levee” condition for levees meeting 44 CFR 65.10 so that the new 
Zone XL can be accurately delineated and the “without levee” profile produced.
*	Provide clarifying guidance that embankments, such as highways, railroads, or natural 
embankments, not specifically designed and engineered to provide flood protection should not 
be modeled and mapped as levees in performing flood insurance studies and restudies 
(Appendix H of the Guidelines and Specifications).
*	Reference USACE Engineer Manual EM 1110-2-1413, “Engineering and Design, 
Hydrologic Analysis of Interior Areas” as acceptable/preferred methodology for interior 
drainage analysis (Appendix H of the Guidelines and Specifications). 
*	Revise the levee mapping and FIRM graphical mapping standards to reflect the new 
Zone XL designation as well as the levee risk classifications (Appendices H and K of the 
Guidelines and Specifications).

3.4.3.	FEMA Procedure Memoranda
Issue a follow-up to Procedure Memorandum 34 that provides further guidance to the FEMA 
Regions and its mapping contractors and CTPs.  Specifically, this further guidance should address:
*	Best practices in evaluating the suitability of existing 44 CFR 65.10 certification data and 
documentation available in FEMA’s records in determining a levee’s continued accreditation 
status. 
*	Cost-effective methods for modeling and mapping levees determined not to meet 
44 CFR 65.10.  For example, approximate or limited detail study techniques could be utilized 
in lieu of full detailed study/restudy methods, especially for levees determined to be in the 
low or medium risk classification.
*	How communities can determine whether an existing levee meets the criteria of 
44 CFR 65.10 and how a certification package should be prepared.


4.	Levee Height and Structural Integrity - The Role 
of Risk Analysis Methodologies
4.1.	Determination of Levee Height
Levees are planned and constructed by Federal, State, and local government agencies, and private 
businesses.  Federal agencies undertake water resource investments for such measures as levees 
within the broad confines of the Principles and Guidelines (U.S. Water Resource Council, 1983) 
(P&G).  P&G generally requires that Federal projects contribute to national economic development, 
which means that they must be economically justified (i.e., benefits should exceed costs).  USACE 
has planned and constructed the majority of Federal levees, and most of the levee systems 
protecting major urban area in the United States.  USACE implementation of the P&G requires that 
flood damage reduction projects, including levees, are planned so that the project scale contributes 
as much as possible to net national economic development (NED) benefits.  For levees, this means 
that the maximization of net benefits is an important consideration in the determination of the height 
and other features of the levee system.  In most instances in urban areas, USACE levee projects 
adhering to these principles are higher than required to meet FEMA base flood  protection 
requirements.  In those urban settings in which levee height is less than FEMA base flood protection 
under these principles, the levee heights are generally increased to ensure FEMA base flood 
protection.  The resulting project must still be economically justified and the local sponsor may be 
required to pay the cost for the difference in levee height between the NED project and the height 
required for base flood protection.
USACE levee projects protecting agricultural areas are often sized to the NED scale without further 
efforts to raise the height to that needed to provide FEMA base flood protection.  For non-Federal 
levee projects, the target is often simply to provide protection from the FEMA base flood so that the 
levee system may be certified and the protected floodplain remain free of development controls.  
There are, of course, many special cases.  Prior to P&G, USACE policy was to seek protection 
from what was referred to as “Standard Project Flood,” or “Standard Project Hurricane” in the case 
of coastal projects.  There are many such projects throughout the country. 
The majority of Federal and local levee systems in non-agricultural areas provide protection from the 
FEMA base flood, or an even higher flood; as a result, the mandatory flood insurance purchase and 
floodplain management requirements of the National Flood Insurance Program (NFIP) no longer 
apply in these areas.  Local governments are often not willing to pay the incremental cost of 
providing additional protection once this level of protection is achieved.  The FEMA base flood has 
increasingly become the de facto design standard for levees.
4.2.	Freeboard
As indicated previously, freeboard is an increment of levee height added to the design flood height to 
increase the likelihood of containing a specified level of flood.  Most definitions of freeboard center 
on height addition to accommodate uncertainty in the design flood elevation.  This, in turn, may 
reflect uncertainty in estimating the design discharge and uncertainty in computing design elevations 
from design discharge.  In USACE design guidance, prior to the risk and uncertainty policies 
discussed below, freeboard was to be designed to reflect the site-specific conditions of each project.  
Small additional height increments above the base-designed freeboard are added to ensure 
protection for critical features such as bridges and water and waste treatment plants during 
overtopping floods.  There are references to 3-feet freeboard in several USACE guidance 
documents, but that does not appear to be stated as a required minimum.  Over time, Federal and 
local agencies tended to implement 3 feet as a minimum freeboard for the majority of levee projects.  
There are notable exceptions:  for the major levees in the Mississippi Valley and the Central Valley 
of California freeboards up to 5 feet are common.
With the publication of 44 CFR 65.10 (FEMA guidelines for levee certification) in 1986, which 
specified a minimum of 3 feet, this number effectively became the default standard for many 
non-USACE levees throughout the United States.  44 CFR 65.10 specifies slightly different 
minimums for coastal environments, reflecting the unique setting of tides, storm surges, and wind 
generated waves. 
4.3.	USACE Risk Analysis Approach – 1996
USACE evolved its present risk analysis policy in response to challenges to flood damage reduction 
project proposals and justification documents by the Office of Management and Budget (OMB) and 
an array of local and special interests,.  The substance of the policy developed over a period of 3 to 
4 years in the mid-1990s and culminated in the publication of ER 1110-2 101, Risk Analysis for 
Flood Damage Reduction Studies, in March 1996, updated in January 2006.  The thrust of the 
policy is to improve decision making and confidence in the project formulation/evaluation process by 
quantifying and disclosing risk and uncertainty in key data and parameters.  The policy and 
associated methods are contained in several USACE Engineer Regulations, Engineer Manuals, 
Engineer Technical Letters, and policy letters.
The fundamental tenets of the policy may be summarized as:
*	Make accurate and unbiased estimates of the probability of flooding and of exposure, and 
publish and communicate those findings.
*	Acknowledge uncertainties associated with a project and its performance, and quantify, 
publish, and communicate that information.  The key items of information that must be 
addressed are discharge-frequency and uncertainty, stage-flow and uncertainty, geotechnical 
and structural performance and uncertainty, operational uncertainty, and project benefits and 
uncertainty.  Other key elements, depending on the specific setting, must also be addressed.
*	Emphasize residual risk (the probability and the consequences of that the project capacity 
may be exceeded) by conducting residual risk analysis and document and communicate 
findings.

USACE recognized that its risk analysis policy and methods had implications for floodplain 
management and the associated task of levee certification, and immediately engaged FEMA 
leadership in discussions.  In 1997, USACE and FEMA agreed on an approach to levee certification 
that embraced risk analysis, and published a policy letter to USACE field offices.  The essential 
elements of the 1997 risk analysis levee certification guidance are:  (2a). Respect the elements and 
principles of 44 CFR 65.10 (i.e., demonstrate a degree of assurance that the base flood will be 
contained); (2b).  Replace the fixed, minimum freeboard criterion of the certification with a 
quantified assurance (Conditional Non-Exceedance Probability – referred to as “assurance”) as 
follows:  Use 44 CFR  65.10 minimums provided that they achieve at least a 90-percent assurance 
of containing the base flood (may require higher, stronger levees); but protection need not be greater 
than that necessary to provide 95-percent assurance of containing the base flood (may certify for 
lower-height levees than 44 CFR 65.10 minimums); and (2c) to the extent possible, quantify and 
include in the analysis uncertainty in the performance of the geotechnical and structural features of 
the levee system.  The risk analysis levee certification policy has been in place since the policy letter 
was issued in 1997.
4.4.	Implementing Risk Analysis Concepts in 44 CFR 65.10
When the 1982 NRC Report was issued, the freeboard approach was the most feasible approach to 
dealing with the uncertainty and natural variability factors involved in the calculation of flood heights 
and structural integrity.  Over time, technology and increased computational capabilities made it 
possible to consider more accurately uncertainty and variability through the application of risk 
analysis methodologies; these methodologies now are generally accepted as a more accurate way to 
establish levee and floodwall heights.  A 2000 study by the NRC, “Risk Analysis and Uncertainty in 
Flood Damage Reduction Studies,” was targeted specifically at USACE initiation of such studies, 
and commended USACE “…for adopting the new techniques and departing from the traditional 
freeboard approach.  The risk analysis paradigm for flood damage reduction studies represents a 
step forward….”
4.5.	Conclusion
The committee concludes that: 
*	Advances in technology and computational capabilities have made possible the widespread 
adoption within the engineering community of risk analysis methodology for determination of 
levee heights and that this methodology represents the appropriate approach for use by 
FEMA in 44 CFR 65.10 in place of the current freeboard methodology.

4.6.	Recommendation
The committee recommends that:
*	FEMA modify CFR 65.10 to phase out use of the freeboard-based approach over the next 
ten years and to substitute the risk analysis methodology at a 90-percent assurance of 
passing the base flood.  During the transition period, FEMA should permit either approach to 
be used in levee design and in recertification analysis.  The existing 44 CFR 65.10 is shown 
in Appendix B.  The committee provides, in Appendix C, two alternative proposed revisions 
to 44 CFR 65.10.  In one, it updates 44 CFR 65.10 to reflect both use of the current 
approach and use of the risk analysis methodology.  In the second, the committee replaces 
entirely the current freeboard methodology with the risk analysis methodology.  It defines the 
risk analysis framework throughout the document.  The revision distinguishes between new 
levees, in which design criteria and levee height required to contain the base flood and the 
associated uncertainty are the primary factors; and existing, aged, and aging levee systems, 
in which the levee system in its as-constructed and currently maintained state and up-to-date 
data about base flood stages and geotechnical and structure integrity are the key factors.  
Freeboard is no longer referenced in favor of quantified assurance related to levee height 
and structural integrity.  The committee includes additional information on what must be 
demonstrated, how to reflect uncertainty in stage and structural integrity, and what the 
specific requirements are for operation and maintenance plans and records.  It also adds a 
new section to define and address residual risk and public safety as an important certification 
requirement.


5.	Computation of the 1-Percent-Annual-Chance 
Flood – Problems and Solutions
Since levee height is normally determined by the elevation of the 100-year flood, accurate 
computation of the 1-percent-annual-chance flood is particularly critical.  Errors in computation 
could lead to undersizing of the levee and, in turn, to the catastrophic consequences of levee 
overtopping or failure.  Errors in the other direction could require a community to build a higher 
levee than required for NFIP compliance.  The determination of the height of the 
1-percent-annual-chance flood requires extensive H&H computations and reliance on baseline 
H&H data concerning the area under study.   Approximately 45 percent of levee designs and flood 
risk determinations are based on precipitation frequency estimates that are as much as 45 years old.  
Approximately the same percentage of designs and determinations are based on flow frequency 
guidelines that are at least 25 years old.  Many communities lack long-term streamflow records.  
This section discusses the problems that have developed in H&H computation and provides possible 
solution to these challenges.
5.1.	Precipitation Frequency Estimates
The precipitation frequency estimates provided by NOAA’s National Weather Service (NWS) 
(www.nws.noaa.gov/hdsc), as shown in Table 5.1, are as much as 45 years old.
Table 5-1.  Current Precipitation Publications

5 – 60 minutes
1 – 24 hours
2 – 10 days
Western U.S.
Frederick & Miller 
(1979) 
Arkell & Richards 
(1986)
NOAA Atlas 2 
(1973)
Tech Paper 49 
(1964)
AZ, NV, NM, UT, Southeast CA
NOAA Atlas 14 
Vol 1 (2003)
NOAA Atlas 14 
Vol 1 (2003)
NOAA Atlas 14 
Vol 1 (2003)
Eastern U.S.
Tech Memo 35 
(1977)
Tech Paper 40 
(1961)
Tech Paper 49 
(1964)
IL, IN, OH, PA, NJ, DE, MD, DC, 
VA, WV, NC, SC, TN, KY
NOAA Atlas 14 
Vol 2 (2004)
NOAA Atlas 14 
Vol 2 (2004)
NOAA Atlas 14 
Vol 2 (2004)
Hawaii
Tech Paper 43 
(1962)
Tech Paper 43 
(1962)
Tech Paper 51 
(1965)
Alaska
Tech Paper 47 
(1963)
Tech Paper 47 
(1963)
Tech Paper 52 
(1965)
Puerto Rico
NOAA Atlas 14 Vol 3 
(2006)
NOAA Atlas 14 
Vol 3 (2006)
NOAA Atlas 14 
Vol 3 (2006)

NWS publishes these estimates at the request of and with funds provided by agencies that use them 
for regulation and design standards.  The oldest standards were published in the early 1960s and 
covered the entire country.  In 1973, there was a major update for the western states and in 2003, 
2004 and 2006 NOAA Atlas 14 provided new estimates for the semiarid southwest, the Ohio River 
Basin and surrounding states, and Puerto Rico and the U.S. Virgin Islands.  NOAA Atlas 14 
introduced new, more reliable, more robust statistical techniques, as well as new techniques for 
spatial interpolation.  NOAA Atlas 14 also provided, for the first time, estimates of the uncertainty 
associated with specific precipitation frequency estimates in different locations.  These uncertainties 
are on the order of plus or minus 25 percent in the upper and lower 90-percent confidence intervals 
in extreme cases.  The publication of uncertainty estimates has highlighted the real uncertainties 
associated with resulting hydrologic estimates of stage, levee height requirements, and potential areal 
extent of flood risk.  As a result, NOAA Atlas 14 provides a basis for dealing with these design and 
regulatory uncertainties, a capability that must be extended to the rest of the country.
NOAA Atlas 14 is currently being updated for Hawaii.  However, updates for large portions of the 
country, as shown in figure 5-1, remain unfunded.  In particular, much reconstruction and re-
estimation of flood risk in the Gulf Coast states is based on Technical Paper 40 published in 1961.

 
Figure 5-1.  Precipitation frequency estimates need updating in large parts of the country.

The long hiatus between publication of NOAA Atlas 2 and the current NOAA Atlas 14 effort led to 
a lack of institutional awareness of the need and responsibility for updating the estimates.  This was 
recognized by the Federal Advisory Committee’s Subcommittee on Hydrology, which, in 2004, 
recommended that NWS update the estimates with funds provided by Federal user agencies.  
However, the funds have not been forthcoming.  Other bodies, such as the American Association of 
State Highway and Transportation Officials Technical Committee on Hydrology and Hydraulics, the 
Transportation Research Board’s Technical Committee on Hydrology, Hydraulics and Water 
Quality, and NOAA’s National Stakeholder Forum, also have recommended updates.  Figure 5-2 
shows that while recently updated estimates are consistent with previous estimates in many areas, 
there are significant changes that could lead to problems in many other areas.
Figure 5-2.  Recent updates show significant changes in precipitation frequency estimates.



5.2.	Estimating Flow Frequency
Hydrologic methods for estimating flow frequency for FEMA’s Flood Hazard Mapping program are 
described in Guidelines and Specifications for Flood Hazard Mapping Partners Appendix C, 
“Guidance for Riverine Flooding Analyses and Mapping.”
The recommended procedures for flow frequency analysis for unregulated gauged streams is 
defined by Bulletin 17B, Guidelines For Determining Flood Flow Frequency, Interagency 
Advisory Committee on Water Data (1982).  Annual maximum peak flows used in the flood flow 
frequency analyses are available on the USGS Web site at http://water.usgs.gov/nwis/sw/peaks.  
The two most commonly used computer programs for performing Bulletin 17B analyses are HEC-
FFA Frequency Analysis (USACE, 1992) and PEAKFQ, Annual Flood Frequency Analysis 
Using Bulletin 17B Guidelines (USGS, 1998). (If the mapping partner determines that Bulletin 
17B is not applicable, then alternative procedures must be justified and documented.)
Bulletin 17B was published more than 20 years ago and significant research has occurred in the 
interim.  There may be more accurate and reproducible procedures available today for defining the 
1-percent-annual-chance flood discharge that is used in levee analyses.  The Hydrologic Frequency 
Analysis Work Group (HFAWG) of the Subcommittee on Hydrology, Advisory Committee on 
Water Information, has proposed a plan for revising Bulletin 17B.  The detailed plan can be viewed 
at the HFAWG Web site at http://water.usgs.gov/wicp/acwi/hydrology/Frequency.  The HFAWG is 
pursuing three major areas of investigations that relate to improved estimates of the 
1-percent-annual-chance flood discharge:  improved procedures for analyzing low and high outliers 
and historical flood data; improved procedures for estimating regional or generalized skew; and 
improved procedures for estimating confidence limits.  These investigations will be completed and 
documented in 2007 and will likely lead to publication of a revision to Bulletin 17B.  The 
development of improved procedures for flood discharges relates directly to risk analysis procedures 
used by USACE for levee certification.  
No nationally accepted procedures for flow frequency analyses exist for streams whose flood 
frequency is regulated by major flood-control structures.  Mapping partners use many different 
methods, depending on the type, quality, and quantity of data available.  USACE Engineering 
Manual No. 1110-2-1415 (USACE, 1993) provides some guidance on flow-frequency analyses for 
regulated watersheds, but additional guidance is needed.  The lack of recommended procedures for 
regulated frequency analysis lends itself to challenges and appeals of hydrologic analyses and to 
delays in publishing FIS reports.  The most reasonable approach for regulated frequency analysis is 
not always clear, given the many circumstances that arise in practice.  HFAWG is also developing 
guidance on flow frequency analyses for regulated watersheds.  
Regional analysis and rainfall-runoff models are the recommended procedures for hydrologic 
analysis for flood hazard mapping of ungaged streams.  Regional regression equations are applicable 
only for unregulated streams; rainfall-runoff models can be used for both unregulated and regulated 
ungaged streams.  USGS Regional regression equations can be found on the Web at 
http://water.usgs.gov/osw/programs/nffpubs.html.  These equations are also included in the USGS 
National Flood Frequency Program (http://water.usgs.gov/software/nff.html).  
Rainfall-runoff models are often used in hydrologic analyses and for levee certifications.  In order to 
use rainfall-runoff model estimates in risk analysis procedures, USACE assumes the equivalent 
years of record and then employs the confidence limits in Bulletin 17B.  The assumption of the 
equivalent years of record is based primarily on engineering judgment.  Although the assumed 
equivalent years of record appear reasonable, additional investigations are needed to quantify more 
accurately the uncertainty of flood estimates from rainfall-runoff models.  
5.3.	Conclusion
The committee concludes that:
*	Much of the baseline information used to determine the1-percent-annual-chance flood height 
is out of date.  This results in levee designs and flood risk determinations that are overly 
expensive or that place those behind levees and in the floodplain at an unacceptable level of 
risk.

5.4.	Recommendation
The committee recommends that:
*	To ensure that the base data used to support the hydraulic and hydrologic analyses reflect 
21st century computation technologies, FEMA, in coordination with other Federal agencies 
that use these data and techniques, should support the funding of NOAA efforts to upgrade 
precipitation frequency estimates, the upgrades to the USGS gaging program, and the 
Advisory Committee on Water Information Subcommittee on Hydrology revision of Bulletin 
17B.  Funding of these efforts will improve the determination of flood recurrence intervals. 


6.	Levee Inventory Database
To effectively manage the variety of NFIP programs, including mapping and floodplain management, 
as well as to support preparedness and response activities, Federal, State, and local officials must 
know where levees are and the condition of those levees.  This section reviews the status of 
documentation of the location and condition of levees and associated structures recognized by the 
NFIP.  It documents prior levee inventory and database activities and current efforts underway to 
inventory the nation’s levees.  This section also makes recommendations on a levee database design 
framework.
6.1.	Existing Levee Inventory Systems and Databases
There are several existing levee inventory and database systems.  These have been established by 
Federal and State agencies with little coordination among the efforts.  Most of these systems are 
incomplete, some are not tied to modern geographic information systems, and overall they provide 
little information about the condition of the levees of the Nation.
6.1.1.	FEMA Levee Inventory System 
FEMA has developed an online database (http://flis.pbsjdfirm.com) to inventory each accredited and 
non-accredited levee structure.  The FLIS captures several aspects of levees: 
*	Characteristics inherent to the levee structure such as levee type, flooding source, bank 
length, freeboard, and certification status, some of which are mentioned in the 44 CFR 65.10 
criteria for levee accreditation and certification
*	Communities that are affected by the levee
*	FIRM panels that are affected by each levee and the protected vs. unprotected area flood 
zones

FEMA Procedure Memoranda 34, 32, and 30 define a process and protocol detailing how MCCs 
are to inventory and document levees using the FLIS system.  With the beginning of Map Mod, that 
responsibility passed from the MCCs to the mapping partners producing the DFIRMs.
The FLIS has a major limitation in that it is not a spatially-based inventory.  While levees are 
referenced by name and include textual descriptions of their location and information on FIRM 
panels, the underlying tabular data is not tied to GIS-based data that permits accurate coordinates 
(latitude and longitude points) of levee centerline locations on the ground.  The spatial aspect of the 
levee location is critical in analyzing the impact of levee structures on surrounding flood-prone areas 
and assessment of risks from levee failures.  Without this tie to a spatial dataset, it can be difficult to 
know which levee or levees a FLIS record is describing and where the beginning and ending points 
of certain levee characteristics are.  
The lack of geospatial explicitness in the FLIS greatly reduces its usability.  Attempts have been 
made to associate levee records in the FLIS with levee records in a GIS dataset so that the 
abundance of attributes in the FLIS may be harnessed, but such attempts have limited success 
because one-to-one association between the two is not always possible.
6.1.2.	Current FEMA DFIRM Data
The FEMA DFIRM database is a GIS-based data model of flood hazard information for NFIP 
communities.  While no specific levee theme or layer exists within the model, the FEMA Guidelines 
and Specifications, Appendix L, specifies how levees are identified within the GIS standards 
DFIRM database.
Specifically, levees are located in a GIS theme called “General Structures” or S_Gen_Struct.  The 
general structures theme includes dams, channels, and culverts, as well as levees.  Levees are then 
identified as a subtype in the general structures layer in a STRUCT_LID field.  This field has a 
code that points to a lookup table of structure codes.  Within a GIS, it is possible to select all the 
levees with the general structures theme by querying levees from the structure type field and saving 
out the query into a separate GIS theme or layer.
The current manner in which levees are modeled in the DFIRM data model presents some 
limitations in the usefulness of the data.  Although the DFIRM data provides accurate locational 
information on levees, few attributes are collected specifically about levees.  Because the theme 
includes the super set of flood-control structures, the data provided specifically on levees do not 
contain enough information to evaluate levee failure.  
6.1.3.	State Databases
The Association of State Floodplain Managers (ASFPM) reported on a survey of State levee 
databases.  To date, Wisconsin and North Dakota have geospatial inventories; Illinois, Mississippi, 
North Dakota, Ohio, and California have some levee database efforts underway.  The vast majority 
of States do not have a levee inventory of any sort.
6.2.	Levee Inventory Systems and Databases under 
Development
The Federal Government is moving ahead with several initiatives to develop comprehensive, 
geospatially based levee inventory and assessment databases.  Federal support of the State of 
California forms the basis for one such effort.
6.2.1.	California DWR Levee Database
The California DWR is developing a statewide levee database.  The effort is being funded with 
support from FEMA Region IX, utilizing FY 2005 Map Modernization Management Support funds.   
The project is a 3-year effort, with most first–year work geared towards capturing accurate spatial 
levee location.
The California Levee Database will show the location and pertinent data for more than 10,000 miles 
of levees within the State.  This project includes the design of an Oracle/SDE Geodatabase that will 
support DWR levee inventory and maintenance activities.
The database will capture various information, including spatial location, engineering, and planning 
information.  The first phase of the project involves capture of levee location and ownership data.  
The second phase of work involves development of standard datasets of interest to various DWR 
operating units.  These datasets will capture risk factors related to each operational interest.  For 
example, the risk factors for floodplain management may include the status of levee certification, 
while the risk factors of maintenance may include the most recent date of levee inspection.
The data development process includes interviews with Federal, State and local agencies that are 
involved with levee maintenance.  Data is captured through an internal Oracle/SDE database.
The design of the database will incorporate design elements from the USACE Special Data 
Standards for Facilities, Infrastructure, and Environment (SDSFIE) data standard, the DWR levee 
information system, and FEMA’s FLIS.  The California database ultimately will be able to input data 
from and output data to these systems.  The California database will also include a Web-based 
interface to distribute levee information over the Internet and provide a mechanism to update and 
maintain this data library.
6.2.2.	U.S. Army Corps of Engineers
USACE is embarking on the development of a nationwide database of flood damage reduction 
structures including levees and floodwalls.  The various USACE districts throughout the Nation 
currently maintain separate levee information both digitally and in paper-based formats.  The Corps’ 
approach is to develop a “proposed geospatial database structure and application framework [that] 
will provide technologies to support the population of a standard, comprehensive, spatially precise, 
authoritative, consistent and temporally explicit levee project database for USACE.”  This database 
structure will allow stakeholders to load, view, modify, and share project-related data, 
documentation, and information.  The system will also provide decision making tools for project 
planning, design, and implementation.”
In 2006, USACE created a levee database design using SDSFIE standards.  USACE will begin the 
inventory process with a survey of all levees in the EP 500-1-1 program (Federal levees, federally 
constructed –locally operated, and levees in the PL 84-99 program).  Five Corps districts will 
populate the database in a pilot effort; the effort then would be expanded to include other Corps 
districts.  The current scope of work for the Corps database will focus on the federally constructed 
levees as well as non-federally constructed levees protecting against a 100-year-or-greater flood 
event.  However, in many States such as California, Federal levees constitute only a portion of all 
levees. 
6.2.3.	FEMA GIS Database
In summer 2005, FEMA initiated an effort to develop a geospatially supported levee database 
framework.  In the process of conducting its initial survey, it became aware of the USACE 
database effort and joined with USACE in defining the structure of the database.  Each of the 
agencies determined that agency-specific data would be developed, but the amount of common data 
merited a cooperative effort.  Since fall 2005, FEMA has been working closely with USACE 
database developers and with the State of California and its developers.  ASFPM is also cooperating 
with FEMA and USACE to ensure that the needs of State agencies are considered in the database 
effort.
To ensure that FEMA’s needs are considered in the Corps database design, FEMA has been 
working with USACE to provide recommendations on the type of data—both entity level and 
attribute level—to be collected.  FEMA is also assisting USACE in identifying where spatial data 
about levees may already exist, providing geometry that may be useful in building the National 
Levee Database.  This data can come from several different sources, such as preliminary and 
effective DFIRM data, States, and local communities.
In the course of its work, the committee has developed specific recommendations on database 
framework technical aspects.  These recommendations are contained in Appendix E.
6.3.	Conclusion
The committee concludes that:
*	Information about the location and condition of levees across the Nation is spotty and not in a 
form that supports effective management and decision making.  Various levee databases 
have been developed but for the most part are not geospatially referenced, are incomplete, 
and lack usable information concerning the condition of the levees and attendant supporting 
structures.  Current efforts by USACE and FEMA to coordinate and develop a 
multi-agency, Federal/State approach to inventory and assessment will provide significant 
benefits.
6.4.	Recommendation
The committee recommends that:
*	FEMA and USACE should continue their efforts to develop a joint database structure that 
will meet the needs of both agencies and other Federal and State organizations to maintain 
an inventory and assessment of flood damage reduction structures, including levees.  While a 
need will exist for agency-specific components of such a database, the management and 
fiscal benefits that accrue from a common core and adherence to the national spatial data 
infrastructure will be significant.  FEMA and USACE database developers should 
incorporate in their database design the recommendations in Appendix E.


7.	Decertification of a Levee
Levees generally are decertified when a community is restudied and it is determined that the levee 
does not meet the levee standards in 44 CFR 65.10, or no available documentation demonstrates that 
the levee meets those criteria.  This section addresses the procedures for decertification, the impact 
of decertification on the local community, and the options available after completion of the 
decertification process.
7.1.	Levee Decertification
For federally funded flood damage/risk reduction systems, the Federal agency usually is responsible 
for notifying FEMA that it is questionable whether the levee currently provides sufficient 
damage/risk reduction.  Once the decision has been made to decertify a levee, a restudy may be 
required to establish BFEs, initiate an appeals period, and provide the community 6 months to amend 
its floodplain management regulations before the revised FIRM becomes effective.  This process 
may take several years.
When the revised FIRM becomes effective, the area that had been protected by the levee is usually 
designated as Zone AE, with BFEs established.  In rural areas where no detailed engineering studies 
have been conducted, the area may be designated as Zone A, without BFEs.  Flood depths behind 
the levee (the difference between the BFE and ground elevation) can range from less than 1 foot to 
20 feet or more.  Flood depths play a significant role in determining the severity of the impact of 
decertification.  The impacts of decertifying a levee include the following:
*	Mandatory Flood Insurance Purchase Requirement.  The most immediate impact is 
that the mandatory flood insurance purchase requirement now applies to the area.  
Individuals must purchase flood insurance in order to obtain mortgage loans from federally 
insured or regulated lenders or other federally related financial assistance.  Lenders would 
review their loan portfolios and require flood insurance on properties now shown as being in 
the SFHA.  Eventually, most properties previously protected by the levee would have to 
purchase flood insurance.
*	Floodplain Management Requirements.  The area behind the levee is now subject to the 
community’s floodplain management requirements.  New and substantially improved 
residential buildings must now be elevated to or above the BFE and non-residential buildings 
elevated or floodproofed to that elevation.  In areas of shallow flooding, this can usually be 
accomplished at minimal additional expense.  However, as flood depths increase, the cost of 
construction will increase and, at some point, it will be not be practicable to meet the 
elevation requirements.  Although some individual property owners may be willing to meet 
the elevation requirements, most developers are likely to delay construction on undeveloped 
land until such time as the level of damage/risk reduction provided by the levee can be 
restored and save them the cost of any protection measures.
*	Flood Insurance Rating.  Existing buildings behind the levee are considered pre-FIRM 
buildings and are eligible for pre-FIRM flood insurance rates and premiums.  Insurance rates 
on these buildings are less than the actuarial rate and the premiums are subsidized.  If 
owners purchased flood insurance for existing buildings prior to the FIRM becoming 
effective and maintained continuous coverage, they could insure the buildings at Zone B, C, 
or X rates, which are substantially lower than pre-FIRM rates.  New and substantially 
improved buildings are subject to actuarial rates based on the elevation of the building in 
relation to the BFE.  Assuming these buildings are built in compliance with the communities’ 
floodplain management requirements (protected to or above the BFE), the premiums should 
be less than those charged the existing pre-FIRM buildings.
*	Property Values and Tax Base.  A decline in property values and the resulting tax base of 
the community may result.  Most studies show that the difference in property values for 
comparable properties inside and outside the floodplain is not great for most flood hazard 
areas.  This likely will be true when a levee is decertified, provided that the properties are 
subject to shallow or moderate depths of flooding.  Some diminution in value of existing 
buildings may result from the identification of the hazard and the expense of a flood 
insurance premium, but the risk is moderated by the ability to purchase flood insurance.  
New buildings in these areas will be subject to some increase in construction costs to elevate 
buildings to the BFE and an annual cost of insurance.  A portion of loss will be reflected in 
loss of value to the undeveloped land.  However, if individual property owners continue to 
believe that the levee provides significant damage/risk reduction even though the levee has 
been decertified by FEMA, this could limit any reduction in property value.
*	Development delay.  The most significant impact likely will be on undeveloped land in 
areas subject to moderate or deep flooding where development is imminent.  Large 
developments may be delayed until the levee is restored.  These areas may experience a 
significant short-term impact on land value. 
*	Impact on Tax Base Will Vary.  Communities with limited areas protected by decertified 
levees or with areas where the flooding is relatively shallow may see only minimal impact on 
their tax base and property tax revenues.  Communities with large areas of deep flooding 
may see a significant decline in tax base and tax revenue.
*	Demands for Protection.  Decertifying a levee generally results in demands from the 
public and local governments that the levee be restored to provide 100-year flood protection.  
When this occurs quickly (within several years or so), the impact of the decertification may 
be transitory.  However, restoration of a levee often will take much longer because of the 
need to obtain funding (particularly if an appropriation from Congress is required) and time 
required for design and construction.  In addition, some levees will never be restored 
because of lack of funding, other economic factors, or the poor condition of the levee.  For 
these areas the impact will likely be long term.

7.2.	Use of Zones AR and A99
As discussed in Section 2, AR zones were established to provide some degree of relief in situations 
where the community demonstrates a level of commitment to restoring the previous level of flood 
protection.  The Zone AR statutory and regulatory requirements were developed largely to reflect 
conditions connected with the decertification of the Los Angeles River and American River levee 
systems.  Both levee systems protected large numbers of people, and the expectation was that 
funding could be obtained and 100-year flood protection restored within a reasonable period of time.
The principal requirements in the statute or in 44 CFR 65.14 for designation as Zone AR are as 
follows:
*	FEMA must determine that the community is engaged in the process of restoring a flood 
damage/risk reduction system that was constructed using Federal funds, recognized as 
providing 100-year protection on the effective FIRM, and decertified by a Federal agency 
responsible for flood protection design or construction.
*	A community that receives Federal funds for the restoration must complete restoration or 
meet Zone A99 requirements within 10 years from submittal of the application for Zone AR 
designation.
*	A community that does not receive Federal funds for the restoration must complete 
restoration within 5 years of the submittal of the application.
*	The community must submit a formal written request for Zone AR designation that includes 
a legislative action requesting the designation and provide supporting documentation that it 
will comply with requirements in 44 CFR 65.14.
*	The community must submit a restoration plan that meets minimum requirements and 
continue to make adequate progress in accordance with the timeframes in the plan.
*	The community must adopt a legal description of areas that are to be designated as 
developed areas within Zone AR and adopt floodplain management regulations compliant 
with 44 CFR 60.3(f).
*	The community must certify annually that the restoration will be completed in accordance 
with the plan.

If, at any time, FEMA determines that the community will not complete restoration in the timeframe 
specified in the plan, FEMA can notify the community that the Zone AR designation will be 
removed and the area mapped as if no flood protection had been provided.
For most communities, the benefits of having the area designated as Zone AR include:
*	Flood insurance will be available at rates no greater than if the project had been completed 
(generally Zone X rates unless an area will still be an SFHA when the project is completed).
*	Floodplain management requirements in Zone AR for developed areas only require that new 
buildings be elevated to 3 feet above natural grade.  No substantial improvements are 
required unless the area is designated as a dual zone in an underlying flood zone (will remain 
an SFHA after the levee is credited).  More restrictive requirements apply outside developed 
areas.  This is a significant benefit in areas of moderate or high flood depths.

The mandatory flood insurance purchase requirement still applies because the area remains an 
SFHA.
A Zone AR area can be converted to Zone A99 once the requirements for Zone A99 are met 
(100 percent of the project cost of the system has been authorized, at least 60 percent of the cost of 
the system has been appropriated, at least 50 percent of the cost of the system has been expended, 
and the system is at least 50-percent completed).  The advantage to the community of converting 
from Zone AR to Zone A99 is that new buildings no longer have to be elevated to meet Zone AR 
requirements.
NFIP regulations currently limit Zone AR to projects that were constructed using Federal funds on 
the grounds that it is more likely that the level of protection would be restored in a timely manner if a 
Federal agency is involved.  This limits the use of the Zone AR designation in situations where 
levees or floodwalls have been built by the community, a local flood-control district, or the private 
sector.  For this reason, many levees that lose their accreditation as a result of Map Mod will not 
qualify for Zone AR designation and will have to be remapped as Zone AE with all that it entails.  
Yuba County, California, is currently upgrading its levees without Federal funding.  Recognizing the 
difficulty in obtaining Federal support, it is considering requesting Zone AR designation even though 
the funding is locally provided.  One way to mitigate the impact of decertification of levees may be 
to remove the requirement that the levee be federally funded while retaining the requirement in the 
statute that a Federal agency determine that the levee is restorable.  Strict requirements could be put 
in place to ensure that the community or flood-control district proceeds with restoration within the 
permissible time frame.  If a community cannot meet these new Zone AR requirements, the area 
would be remapped as Zone AE.
7.3.	Recognition of and Dealing with the Impact of 
Decertification
The sections above highlight the legal and regulatory impact of decertification, including the 
requirement for mandatory insurance and the imposition of land use controls.  The sections did not 
include discussion of the secondary social and economic impact that might result from those actions.  
Homes with Federal mortgages will have to purchase insurance, and the rates may be high.  
Furthermore, resale value of such property may be lessened due to the high insurance cost.  In 
addition, pending development must comply with floodplain land use regulation, which may result in 
an increase in cost or cancellation of the development. 
As communities face the challenge of recertifying their levees and, in some cases, restoring levees 
that fail to meet certification requirements, it would be unrealistic to assume that all, or even many, 
communities have the financial capability to remedy deficiencies without some Federal involvement.  
The potential Federal sources of funding, the USACE Flood Damage Reduction program and the 
FEMA Flood Map Modernization initiative, today face severe budget constraints. 
The net effect of these actions and other actions needed to bring the community into compliance will 
certainly generate stress within the community and a cry for political action to prevent 
decertification.  While this outcome should be recognized and ameliorated where possible by 
remedial action to recertify the levee, there must also be a clear recognition that decertification 
identifies a risk to the community that can not be ignored.  Working to deal with both of these issues 
will require close cooperation among FEMA, USACE, the States, local governments, and elected 
representatives.
7.4.	Conclusions
The committee concludes that:
*	Under Procedure Memorandum 34, when a levee is about to be remapped, levee sponsors 
must provide to FEMA documentation of previous certification of the levee and evidence 
that the levee currently meets the 44 CFR 65.10 criteria.  Where such certification 
information does not exist (e.g., a grandfathered levee), the sponsor must provide 
certification.  In other cases, the initial documentation may be incomplete or a physical 
inspection of a levee is inconclusive as to its condition.  Under these circumstances, the 
levees will have to be recertified.  Since the certification process may require a lengthy 
period of survey and analysis, completion of a countywide project may be delayed until the 
certification information is provided for what may be only one panel. 
*	When the physical condition of the levee indicates that the levee will not be certifiable, the 
recognition of the levee should be immediately removed.
*	When the issue of certifiability is in question and could be resolved positively or negatively, 
action should be taken to resolve the issue, either by considering the levee as not providing 
protection or by initiating remedial action and seeking Zone AR or A99 status.  In this case, 
to deal with the requirements of map production, three approaches could be taken:
?	Wait for certification documentation to be provided and delay completion of either the 
FIRM panel or the countywide map.
?	Move forward with issuing the panel, showing the levee as not providing protection 
from the 1-percent-annual-chance flood and making the community subject to 
mandatory insurance provisions at Zone A rates.
?	Issue the panel, designating the area as a special zone and indicating that the 
certification is in progress and that the action must completed within a 2-year period or 
the area reverts to unprotected status.  Under this option, the community would be 
responsible for notifying all residents of the lack of certification and the potential 
residual risk.
*	The process of conducting certification activities and, if required, restoration of decertified 
levees will place a heavy burden on local communities.  These communities are already 
turning to the Federal Government for support, and the Federal Government should expect 
these requests to increase.  These requests will place heavy burdens on related FEMA and 
USACE programs that are already stretched thin fiscally.

7.5.	Recommendations
The committee recommends that:
*	When communities are not immediately able to document that currently certified levees can 
be recertified and the levees are not known to be at risk, FEMA should notify the 
communities of the need for a more detailed examination of the levees and provide a specific 
schedule for that activity.  Communities should be required to notify all persons who are in 
areas behind the levees of the re-examination process and identify for them the residual risks 
and the lack of information about the levees. 
*	FEMA should consider seeking legislative action to permit use of A99 designation and 
procedures by communities that are able to self-fund levee upgrades.
*	FEMA and USACE should review existing authorities and funding available to assist 
communities in performing certification analysis and make recommendations to OMB and 
Congress if the funding and authorities are not available.  FEMA and USACE should also 
develop expedited processes to assist communities in remediation of publicly owned levees 
and seek OMB and congressional approval of these processes and recognition of the need 
for resource commitments to support them. 



8.	Public Awareness and Outreach
8.1.	FEMA and Outreach
As the Federal agency responsible for administering the NFIP, FEMA identifies areas prone to flood 
hazards nationwide and then develops and distributes flood hazard and flood risk information about 
the affected areas in an appropriate manner.  Since the 1970s, flood hazard maps and collateral 
reports have been the primary vehicles to distribute flood hazard and risk information to the 20,000 
communities participating in the NFIP.  In addition to issuing guidelines and standards documents, 
FEMA has developed and distributed—through a variety of sources—hazard-specific public 
awareness and outreach materials in an effort to improve the awareness of community officials and 
citizens nationwide.
FEMA is not responsible for the design, construction, or maintenance of levees and comparable 
flood-control structures, or for creating, implementing, or enforcing State and local floodplain 
management regulations.  FEMA does not certify levees, but relies on certification provided by the 
local sponsor of a levee or an appropriate Federal agency.  Therefore, from FEMA’s perspective, 
levee-related public awareness and outreach activities have primarily been the responsibility of the 
Federal, State, and local agencies with the primary responsibility for these structures and systems.  
FEMA has only become involved in the information dissemination process when specific structures 
or systems are out of compliance with NFIP regulations and mapping standards and create 
significant changes to the floodplain boundaries shown on the FIRMs for the affected communities.  
In those situations, FEMA’s primary activities have been to explain why the FIRM is changing, 
clarify the NFIP regulations, and inform community officials and others what they must do to get the 
structure or system back in compliance with NFIP regulations and to reduce the mapped floodplain.
FEMA has not undertaken a wide-scale, nationwide effort to inform community officials and citizens 
about such topics as the relative protection provided by levees and similar flood risk-reduction 
systems, the inherent risk in building on the landward side of these systems, and alternative 
floodplain development practices that should be considered in levee-affected areas.
As documented elsewhere in this report, flood-related disasters continue to occur in areas where 
such structures and systems have been constructed, and the loss of life and property has been 
significant.  The disastrous impact of levee failures in New Orleans made it apparent that 
community officials and citizens nationwide must be better informed.  This does not mean that 
FEMA should take on this burden alone.  In fact, research has shown that local champions are most 
successful in conveying such messages.  However, by combining their resources, FEMA, its Federal 
and State agency partners, and active nongovernmental organizations such as the professional 
associations participating in the Mapping Coalition (e.g., ASFPM, National Association of Flood and 
Stormwater Management Agencies (NAFSMA)) working together can craft the appropriate 
messages, identify the appropriate delivery vehicles, and deliver messages to affected community 
officials and citizens nationwide.
The execution of Map Mod activities heightens the necessity for outreach, because the procedures 
being used to re-evaluate existing levees (documented in FEMA Procedure Memorandum No. 34) 
have, for the most part, placed new responsibilities on States, communities, and levee 
owners/sponsors.  The potential for no longer recognizing the flood protection capabilities of 
levees—with pertinent changes in flood insurance and floodplain management requirements for the 
affected areas—has also raised the awareness of the public and of elected officials at all levels.  A 
sound, comprehensive public awareness and outreach program, initiated prior to or concurrent with 
any FEMA actions regarding levees, will reduce the stress of all parties and minimize delays in the 
production of updated maps.
8.2.	Strategy Development and Implementation
As FEMA moves forward to develop and implement policy, regulatory, and procedural changes, it 
must also implement a public awareness and outreach strategy to improve community officials’ and 
citizens’ awareness and understanding of levee-associated hazards and risks and to inform them of 
the processes of conducting levee assessments.  FEMA should also work with its Federal, State, 
and local partners—both governmental and nongovernmental—to build on these partners’ 
successes, avoid their mistakes, and lead the development of a comprehensive, synergistic strategy 
that can and will be implemented consistently wherever levee structures and systems are located.  
The public awareness and outreach program must also involve the transmission of information from 
governmental and nongovernmental organizations to the public about the residual risks landward of 
levees and the level of those risks, even after a levee is credited on the map with providing 1-
percent-annual-chance or greater flood protection.
Listed below and in Appendix D are some initial steps to be considered for carrying out the public 
awareness and outreach program:
8.2.1.	Awareness and Outreach Approach
The primary purpose of public awareness and outreach activities should be to:
*	Explain the relative advantages (benefits) and disadvantages (risks) of levee structures and 
systems
*	Emphasize the possibilities of levee overtopping and failure and the catastrophic aftermath of 
such events
*	Elaborate on structural and nonstructural alternatives in levee-affected areas
*	Foster stakeholder understanding of State and local policies, regulations, procedures, and 
responsibilities in regard to the construction and maintenance of levee structures and systems
*	Foster stakeholder understanding and acceptance of Federal (FEMA, USACE, and other) 
policies, regulations, and procedures in regard to the evaluation of levees and the mapping of 
levee-affected areas, with specific emphasis on the accreditation process and any changes 
that may occur in the future
*	Enable communities and other partners to acquire, prepare, and submit supporting documents 
to evaluate or reevaluate levees as a result of the policy, regulatory, and procedural changes
*	Foster stakeholder understanding of the floodplain management and insurance impacts of 
changing the flood hazard information shown on the flood map for levee-affected areas
*	Encourage, through collaborative efforts, community-wide education of property owners, 
developers, builders, and other affected citizens in regard to levee-related risks and 
protective actions

In line with the overall Map Mod strategy for outreach and risk communication, the levee-related 
public awareness and outreach activities and all materials developed in support of these activities 
should be based on the following assumptions:
*	Information about true flood hazards, as presented on flood maps and in FIS reports, is 
critical for making informed risk management decisions. 
*	Flood hazard information must be accurate, accessible, and understandable to a wide range 
of stakeholders.
*	To realize the full, long-lasting benefit of modernized maps, the user community must be 
expanded and better informed.
*	Collaboration and the engagement of stakeholders will enable messages to reach the 
affected public.
*	As indicated in the more detailed information provided in Appendix D, Federal, State, and 
local agencies and nongovernmental organizations that are involved with the construction and 
maintenance of levee structures and systems should collaborate on the following actions:
?	Clearly define the messages that are to be delivered, and train FEMA personnel how 
best to distribute them
?	Identify the audiences to whom the messages must be delivered
?	Define the roles and responsibilities of all public- and private-sector organizations and 
individuals that should be involved in this effort
?	Identify the most effective delivery vehicles
?	Identify potential roadblocks, and discover actions that should be taken to mitigate or 
eliminate these roadblocks
?	Establish mechanisms for collecting feedback to measure the success of the public 
awareness and outreach activities and vehicles
?	Implement a system that uses the collected feedback to improve messages, activities, 
and delivery vehicles
*	Explain to the public the difference between “certifying” and “crediting” a levee on NFIP 
maps.
*	On this committee’s recommendation, explain to stakeholders the transition from a 
freeboard-based approach to a risk analysis approach.

The committee recognizes that this is a bold, large-scale undertaking that departs from current 
practice.  However, the committee likewise believes that such action must be taken to increase the 
safety of people throughout the Nation.
8.3.	Conclusion
The committee concludes that:
*	The initiation of levee reevaluations, as outlined in Procedure Memorandum No. 34, 
significantly modifies the procedures initially discussed with communities and levee 
owners/sponsors and has the potential to create significant public opposition to the NFIP and 
Map Mod.  A fully funded, well-executed public awareness and outreach program should be 
implemented immediately to accompany the execution of Procedure Memorandum No. 34, 
levee reevaluation activities, and the implementation of the recommendations in this report.

8.4.	Recommendations
The committee recommends that:
*	FEMA, working with its Federal, State, and local partners and levee sponsors, should 
develop and implement a public awareness and outreach strategy that will improve public 
officials’ (including the Administration and U.S. Congress) and citizens’ awareness and 
understanding of levee-associated hazards and risks.  As part of this public awareness and 
outreach effort, levee sponsors should be required, through changes to the NFIP regulations, 
to annually notify property owners in areas behind a levee of the nature of the residual risk 
that exists and the risk classification of the levee.
In executing future public awareness and outreach activities, FEMA should carefully consider the 
procedural recommendations listed above and the recommendations listed in Appendix D.


9.	Handling of Counties Where Maps Have Become 
Effective
Because the Flood Map Modernization initiative has been underway for more than 2 years, mapping 
has been completed or is in process for nearly 400 counties where levees existed.  It is likely that, at 
the time the mapping was completed, neither the existing certification documents nor the 
development of information to support recertification were thoroughly reviewed.  The local residents 
who rely on these maps can only assume that, if the maps are issued, FEMA has reviewed with 
“due diligence” the condition of the levees involved.
Fortunately, fewer than a quarter of the maps have become effective, with the remainder 
somewhere in the study or adoption process.  The committee believes that it would not make sense 
to stop all work on countywide maps until a detailed levee review has been completed for the panels 
with levees.  Rather, FEMA should seek local adoption of the new maps, without the panels 
containing levees, and should concurrently notify the relevant adopting communities that a more 
detailed examination of their levees is needed, and provide a schedule for that activity.  Communities 
should be asked to notify all people residing in areas behind levees of the reexamination, and to 
explain to them the residual risks and the lack of information about their levees.  This action might 
closely parallel ongoing FEMA efforts to support the completion and adoption of new countywide 
maps that contain levees needing further study.


10.	Overarching Issues
Several topics arose during the conduct of committee activities that, although not specifically part of 
the task given to the committee, merit comment.  They are the adequacy of the level of protection 
provided by levees, the residual risk that exists for those behind levees, the treatment of future 
conditions, “system” reliability, interagency cooperation, and the need for research and development 
(R&D) on rapid levee geotechnical assessment.  While two of these topics are addressed directly 
by this report, all merit attention by FEMA and other Federal agencies.
10.1.	Level of Protection
Under the NFIP, the SFHA was defined as the area encompassed by the 100-year flood.  It thus 
seemed logical, when the decision was made to recognize that properly constructed levees reduce 
the risk to those behind levees, that when those levees provided protection against at least the 
100-year flood, the levees could be assumed to remove the protected areas from the floodplain of 
the 100-year flood and the requirement for insurance.  Unfortunately, the primary motivation for 
some communities to construct or upgrade a levee system has been the desire to have the levee 
credited by FEMA as providing 100-year protection, so that the NFIP floodplain management and 
mandatory flood insurance purchase requirements no longer apply.  Once this has been achieved, 
many communities view additional levels of protection as an unnecessary expense.  FEMA’s 
minimum standards for levee accreditation have become the de facto design standard for levees in 
many instances, even though higher levels of protection might be advisable because of the residual 
risk of flooding and the threat to lives and property.
As history has indicated, when a flood greater than the 100-year flood occurs, the risk to a home 
with a first-floor elevation at the level prescribed for the 100-year flood may be far smaller than the 
risk to the individual whose home is behind an overtopped levee, who will face flood elevations that 
could be measured in tens of feet.  The nation’s experience with catastrophic flooding after levee 
overtopping and breaches highlights the residual risk to those behind levees.  Ever since the BFE 
was established as the minimum level for levees to be recognized by the NFIP, the need to require 
levees to provide protection to an elevation higher than the 100-year standard has been discussed.
As indicated in Section 2, FEMA expressed great concern about the fragility of levees in 1981, 
noting that levee overtopping or failure is involved in approximately one-third of all flood disasters.  
FEMA stated that:
*	The 100-year flood is generally found to be a low design standard for structures protecting 
densely populated areas, because of the relatively low cost of raising or upgrading the levee 
compared to the cost of damages that can that can be prevented
*	Only a fraction of all earthen levees built with crown elevations at the computed 100-year 
flood elevation can be expected to provide protection for the true 100-year event because of 
the following factors:
?	the uncertainty involved in establishing flood elevations
?	changing hydrologic conditions
?	the possibility of structural failure before overtopping

In June 1977, USACE reported to HUD that “setting the design of levees in urban areas at the 
100-year level could be imprudent since that is not a high degree of protection.”  USACE also stated 
that a larger flood, such as the Standard Project Flood (SPF), should be adopted as the required level 
of protection.  In September 1977, the Director of FEMA’s Engineering Division recommended that 
the NFIP recognize only levees designed to provide protection against the SPF.  In 1979, USACE 
issued a policy memorandum stating, “On the assumption that exceedance of the design flow would 
cause a catastrophe, the standard project flood (SPF) is the desirable minimum level of protection 
that should be recommended for high levees, high floodwalls and high velocity channels in urban 
areas.”  Shortly thereafter, the FIA Administrator recommended to the Director of FEMA 
“consideration of a standard in excess of the 100-year flood, such as the Standard Project Flood, for 
local protection works to be recognized by FEMA.”
In 1994, following the failure of levees throughout the Midwest, the Interagency Floodplain 
Management Committee stated in its report to the White House that urban centers should, at a 
minimum , be equipped with levees providing protection against the SPF.
Following Hurricane Katrina, ASFPM and NAFSMA publicly recommended that the minimum level 
for recognition of urban levees should be the 500-year flood level.  The State of California is 
considering requiring levees that protect urban areas to be at least at the 200-year level.
Moving to a higher level of protection may not meet the guidelines established in the Federal 
Economic and Environmental Principles and Guidelines for Water and Related Land 
Resources Implementation Studies unless, as recommended in several recent NRC studies, the 
guidelines are revised to better consider social and economic costs and benefits.
This committee has not had the opportunity to study the subject in detail, but it believes that strong 
consideration should be given to requiring that levees provide protection against floods greater than 
the 100-year flood.  The committee believes that FEMA should give strong consideration to not 
recognizing, for NFIP purposes, levees protecting highly urbanized areas unless they can protect the 
area against events greater than 100-year floods (e.g., 500-year floods).  As indicated above, a long 
history of recommendations and analyses support the need for protection to 500-year or higher 
levels.  Given the large number of levees in existence, the transition would not be quick or easy.  
Nevertheless, FEMA should immediately take steps to examine this issue in detail and to determine 
whether a change in the standard for recognition should take place.
10.2.	Dealing with Residual Risk
Previous sections have referred to the need to deal with the residual risk for individuals and 
structures behind levees.  The committee believes that FEMA should:
*	Take steps to ensure that those living behind levees are formally notified about the residual 
risk they face and the level of protection they are being provided
*	Consider requiring some level of insurance for those protected by levees 
*	Require communities to establish special early-warning systems and to develop a flood 
warning preparedness plan for those protected by levees
*	Examine approaches for indicating on DFIRMs the nature of the residual risk in an area 
protected by levees (as indicated earlier in the report, these areas could receive a special 
zone classification)
10.3.	Future Conditions
Current FEMA regulations do not require the hydrology of potential future climatic conditions to be 
analyzed or the effects of potential upstream or downstream development on the H&H of the area 
under study to be considered.  However, these factors work together to change (likely reduce) the 
level of protection provided by structures such as levees and modify (likely raise) the elevation of 
the 100-year flood.
Although considerable debate continues over the parameters or even the existence of climate 
change, climate variability is a fact and has been reflected in the recent increases in storms and 
changes in the nature of annual precipitation patterns.  National climate change assessments 
forecast increases in weather events that lead to flooding, and recent studies indicate increases in 
the severity of coastal events.
The expansion of major urban areas into nearby rural areas has also changed the pattern of runoff in 
communities across the nation. Some future conditions hydrology has been developed by 
communities interested in using the data to better identify future land use challenges. A study on the 
impacts of future development being completed for FEMA by ABSG Consulting as part of the 
Evaluation of the National Flood Insurance Program provides an important perspective on this issue. 
The study, which uses HAZUSTM modeling and common assumptions about the effect of 
development on runoff, indicates that building in a watershed is expected to change the flood 
conditions and, in some cases, can increase the damage to structures by multiple orders of 
magnitude depending on the flood conditions.  Examination of modeling results from several counties 
or parts of counties indicated that future conditions flooding from the 100-year flood event increase 
flood damages relative to the existing conditions flooding by somewhat modest percentages to very 
large percentages, depending on the expected development and specifics of each area.  Although 
these findings cannot be generalized nationally, they are expected to be broadly representative of 
findings in other parts of the country.
It is also important to understand that rural, suburban, and urban areas are in a continuum and to 
recognize the relationship among levee systems along a river.  While agricultural levees may not 
appear to have any immediate relationship to downstream suburban or urban levees, the failure of an 
agricultural levee may have a pronounced effect on the suburban or urban areas downstream, if the 
floodwaters remain landward of the levee as they move downstream.  This situation occurred during 
the 1993 Mississippi River flood.  This type of understanding calls for comprehensive floodplain 
modeling, using digital mapping products and GIS, and analyzing different potential failure scenarios.
The committee recognizes that dealing with climate change, sea-level rise, linked levees, and future 
development requires the commitment of significant resources and represents a conceptual shift 
from basing criteria on present conditions to basing criteria on possible, but not fully quantifiable, 
future conditions.  Nevertheless, the committee believes that this step must be taken and 
recommends that FEMA, in coordination with other Federal agencies, States, and communities, 
should closely examine how to undertake such efforts.
10.4.	System Reliability
The effectiveness of a levee system depends on the effectiveness of all of the components of that 
system.  These components include the levees and floodwalls themselves, openings through the 
levees that must be blocked during a flood by gates or other structures, pipes that run through the 
levees, and features such as railway and highway embankments; the failure of any of these would 
cause the system as a whole to be compromised.  FEMA’s recognition of a levee should be 
predicated on its own review of all the components of the system and, of special importance, the 
links among these components.  As the post mortems on the New Orleans levees indicated, the 
system as a whole was threatened by the failure to deal with locations where differing components 
met, or to ensure that critical system elements, such as gates, were available and could be installed. 
The same issues arose during the 1993 Mississippi River floods, when a gate failure caused the 
flooding of the Des Moines, Iowa, water treatment facility.  Given the current staffing of the FEMA 
Regional Offices, such an approach will require significant but necessary resource increases.
10.5.	Federal, State, and Interagency Cooperation
The structure of this committee and the participation of non-Federal observers opened the 
committee’s discussions to a wide variety of viewpoints.  The agencies’ competing and 
complementary efforts to deal with the levee challenge were placed on the table.  By bringing 
together Federal and State agencies in the development of a levee inventory and assessment 
process, this committee recognized the potential benefits to all parties in a cooperative effort.  A 
considerable exchange of information took place with respect to the challenges faced in computing 
the 100-year flood and dealing with the geotechnical considerations of levee certification.  The 
committee recommends that participating agencies seek opportunities to conduct such joint efforts 
with a view to strengthening the ongoing relationships among groups working on these issues.
10.6.	Research and Development – Geotechnical Assessment 
   of Levee Integrity
Early in its deliberations, the committee recognized that a major challenge facing those responsible 
for levee certification was the performance of appropriate and rapid geotechnical assessments of 
levee integrity.  Such assessments, depending on the nature of the material and the cross section of 
the levee, could cost more than $100,000 per linear mile of levee, with the bulk of the costs related 
to the number and depth of soil borings and the determination of levee centerline elevations.  The 
committee sought out current efforts, nationally and internationally, to address these issues, and 
found that no methods or technologies are currently available to replace soil borings.  However, the 
LIDAR efforts of the U.S. Army Engineer Research and Development Center (ERDC) and USGS 
have reduced the costs and increased the speed of determining levee elevations.
The committee learned that a Canadian firm, Fugro Airborne Surveys, has developed 
electromagnetic induction sensing techniques, using a suspended, multicoil sensor platform hung 
below a helicopter, to perform conductivity surveys over levees.  The ERDC has demonstrated the 
utility of airborne and ground-based geophysical methods to determine soil composition and 
floodplain properties, and has developed an approach for the initial screening of levee integrity in 
levees controlled by the International Boundary and Water Commission along the U.S.-Mexico 
border.  However, USACE has not directly funded any R&D program to further the 
research ERDC has made in this area or to develop techniques to characterize unstable levee 
signatures.  Similar R&D efforts are underway in Japan, at a low level of funding, by the Public 
Works Research Institute.  A California firm, DOER Subsea Robotics & Submersible Systems, has 
proposed to the California DWR the use of several techniques for such investigations.
Research also is needed to support the use of the geotechnical data in risk assessments.  
Methodologies must be developed to apply and compare remote and in situ sampling datasets with 
previous levee performance/failure data (from a GIS-managed databank) and failure models, to 
develop fragility curves and assign sector risks.
The task facing those responsible for levee assessment is monumental.  The costs may be equally 
high.  The performance of lengthy assessments can only delay the completion of map modernization.  
The committee believes that increased R&D resources should be focused on further developing the 
above-mentioned techniques and applying them to ongoing assessment efforts.  The benefits of the 
program, if only minimally successful, could far outweigh the costs. 


11.	Next Steps
The committee cannot overemphasize the importance of dealing with the “levee issue” in a rapid 
and straightforward manner.  On the other hand, the committee recognizes that new regulations 
cannot, in the Federal system, be developed and promulgated overnight.  FEMA and other 
governmental agencies need to move where they can and to launch efforts to deal with items that 
will require a longer timeframe to accomplish.  Given these constraints, the committee recommends 
that FEMA address the issues identified in this report in the manner described below.
11.1.	Immediate Actions
The Committee urges FEMA and, as appropriate, other Federal agencies to take the following 
actions immediately:
*	When communities are not immediately able to document whether currently certified levees 
can be recertified and the levees are not known to be at risk, FEMA should notify the 
communities of the need for a more detailed examination of the levees and provide a specific 
schedule for that activity.  FEMA should require these communities to notify all people in 
areas behind the levees of the reexamination and identify for them the residual risks and the 
lack of information about the levees.
*	FEMA should define, as a matter of policy, a new flood insurance zone (Zone XL) for areas 
behind levees that meet the requirements for inclusion in the NFIP.  Zone XL would include 
those areas behind the levee that would be subject to inundation by the 100-year flood if 
there were no levee.  The area between the 100-year and 500-year lines should be shown as 
a shaded Zone X.
*	FEMA should initiate the revision of 44 CFR 65.10 and other appropriate FEMA guidance 
and specification documents, to address technical changes to the CFR recommended by this 
report.
*	As a matter of policy, FEMA should require levee sponsors to conduct annual inspections of 
their levee systems; biennially submit to FEMA the results of the annual inspections, levee 
system operation and maintenance records, and an assessment of the levee systems during 
any flood events that occurred within the reporting period; and every 10 years submit a 
report that recertifies the engineering and geotechnical conditions of the levee system.
*	FEMA and USACE should continue their efforts, in coordination with the States, to develop 
a joint database structure that will meet the needs of both agencies and other Federal and 
State organizations to maintain an inventory and assessment of flood damage reduction 
structures, including levees.
*	FEMA, working with its Federal, State, and local partners and levee sponsors, should 
develop and implement a public awareness and outreach strategy that will improve the 
awareness and understanding of public officials (including the Administration and Congress) 
and citizens.  The following issues should be included:
?	Levee-associated hazards and risks (as part of this public outreach effort, levee 
sponsors should be required, as a matter of policy, to provide annual notification to 
property owners in areas behind a levee of the nature of the residual risk that exists)
?	The current procedures to map and recertify existing levees and the attendant 
challenges created by decertification
*	FEMA and USACE, recognizing the important State and local roles, should develop 
incentives and support mechanisms to ensure that State and local agencies effectively carry 
out their responsibilities with respect to levee operation and maintenance.
*	FEMA should exclude embankments, such as roads and railroads, from the accreditation of 
new levee systems unless those embankments are engineered specifically to provide 
damage/risk reduction from flooding and meet the engineering criteria required of levees.
*	FEMA, USACE, and USGS should support R&D efforts focused on improving the rapid 
assessment of levee geotechnical integrity and should jointly recommend that the National 
Science Foundation pay attention to this area of research.
*	As a matter of policy, FEMA should require communities to establish special early warning 
systems and to develop evacuation plans for those protected by levees.
*	FEMA should develop and disseminate levee certification guidance for communities and 
engineers.

11.2.	Longer-term Actions
The committee, recognizing the need for additional study and regulation development, urges FEMA 
and, as appropriate, other Federal agencies to initiate action on the following longer-term 
recommendations and to take the following actions:
*	FEMA should revise 44 CFR 65.10 to phase out, over the next 10 years, the 
freeboard-based approach and to substitute the risk analysis methodology, with a 90-percent 
assurance of passing the 100-year flood, to determine the required levee heights.  During the 
transition period, FEMA should permit either approach to be used for levee design and 
recertification analysis.
*	FEMA should take immediate steps to examine the feasibility of not recognizing, for NFIP 
purposes, levees that protect highly urbanized areas unless they provide protection from 
events greater than 100-year floods (e.g., 500-year floods).
*	FEMA should address the challenge of the residual risk to structures behind levees by 
seeking legislative change to require property owners to purchase some level of flood 
insurance for structures behind levees (in the new Zone XL).
*	FEMA, working closely with other Federal agencies, States, and communities, should 
examine how best to deal with climate change, sea-level rise, linked levee systems, and 
future development as major drivers of future conditions H&H, with a goal of determining a 
BFE based on possible, but not fully quantifiable, future conditions.
*	FEMA, in coordination with other Federal agencies, States, and communities, should initiate 
studies to determine how levees could be identified under a scientifically based levee risk-
classification system (e.g., high, medium, or low).  This system would be based on factors 
that include the potential depth of flooding in the event of failure or overtopping; the type and 
density of development in protected areas behind the levee; steps taken to ensure that levee 
failure does not occur when the levee capacity is exceeded (overtopping); warning times; 
and the number and types of egress so that people who may be inundated may move out of 
harm’s way.  This levee risk classification would be designated on the FIRM and published 
in the FIS report.
*	FEMA, in coordination with other Federal agencies that use H&H data and techniques, 
should support funding of NOAA efforts to upgrade flood frequency estimates, upgrade the 
USGS gaging program, and revise Bulletin 17B, which guides flood recurrence interval 
determinations.


Appendix A.	Interagency Levee Policy Review 
Committee 
Members

Organization
Activity
Representative
FEMA
Mitigation Division
Kelly Bronowicz – Project Monitor*

Mitigation – Risk Reduction
Lois Forster

Mitigation – Risk Insurance
Donald Beaton

Region V
Ken Hinterlong

Region VI
Gary Zimmerer

Region VII
Rick Nusz

Region IX
Cynthia McKenzie
Nat’l. Service Provider 
(Michael Baker, Jr., Inc.)
Consultant
Gerry Galloway, Chair

Project Management
David Preusch*

Project Management
Jim Murphy

Project Management
Jerry Sparks (Dewberry)

Engineering
Will Thomas

Engineering
Ed Mifflin

Engineering
Mike Robinson

Outreach
Richard Wild

GIS
Travis Clark (RMC 9)

Executive Assistant
Sherri Harris
USACE
HEC
Darryl Davis

HEC
Chris Dunn

IWR
Ron Conner*

HQ
Steve Durrett

Rock Island District
Marvin R. Martens
NRCS
Watersheds
Andrew Johnson*

Engineering
Bill Irwin
USGS
Surface Water
Phillip Turnipseed*

Mapping
Rick Pearsall
NOAA
NWS – Hydrology
Geoff Bonnin

NOS – Ocean Products
Michael Szabos
HUD
Comm. Planning & Devel.
Danielle Schopp*


Charles Bien
DOT
FHWA – Hwy. Infrastructure
Jorge Pagan-Ortiz
BuRec
Operations
Robert Quint
TVA
Floodplain Management
Roger Milstead
IBWC
Engineering
Steve Smullen

Engineering
Jose Nuńez



* Organizational Lead





Subject Matter Experts/Observers

Organization
Representative
Association of State Floodplain Managers
Paul Osman*
Larry Larson
George Riedel
National Association of Flood and Stormwater 
Management Agencies
Susan Gilson*
Pete Rabbon
Flood Risk Education Alliance
Clive Goodwin (FM Global)
National Association of Home Builders
Christopher Galik
National Association of Realtors
Russell Riggs
First American Title Insurance
Chris Small
State of California
Ricardo Pineda (DWR)
Michael DePue (PBS&J)
State of Louisiana
Clyde Martin, Federal Programs Office*
Larry Ardoin
State of Missouri
Dale Schmutzler, MEMA
State of Wisconsin
Robert Watson, Floodplain Management

Consultants

Organization
Representative
FEMA
Rita Henry, Bill Blanton, Tom Hayes,  
Ray Lenaburg (Region IX)
NSP
Jeff Sparrow, Tom Smith
USACE
Tim Pangburn (CRREL), Nancy Blyler (HQ), 
Joe Dunbar (ERDC), Joan Pope (ERDC)

Document Development

Organization
Representative
Editorial Review and Production
Susan Ellicott, Joshua Fernatt,  
Shannon Halloran, Robert Hickman,  
Samantha McCullough, Lee Nesbit,  
Mack Rhoades, Michael Richards,  
Todd Steiner, Mead Summer
Administrative
Gena Croom


* Organizational Lead





Appendix B.	44 CFR §65.10
 
 




 



 


Appendix C.	Proposed Revisions to 44 CFR §65.10, 
Mapping of Areas Protected by Levee 
and Floodwall Systems
Revision 1 – Interim Changes
44 CFR §65.10	Mapping of areas protected by levee systems
	(a)	General.  For purposes of the NFIP, FEMA will only recognize in its flood hazard 
and risk mapping effort those levee and floodwall systems (hereafter referred to as flood risk 
reduction systems) that meet, and continue to meet, minimum design, operation, and maintenance 
standards that are consistent with the level of protection sought through the comprehensive 
floodplain management criteria established by §60.3 of this subchapter.  Accordingly, this section 
describes the types of information FEMA requires to recognize, on NFIP maps, a levee system that 
provides protection from the 100-year flood, while concurrently recognizing the residual risk that 
continues to exist.  The community or other party seeking recognition of such a levee system must 
provide this information to FEMA at the time a flood risk study or restudy is conducted, when a map 
revision is sought on the basis of a levee system, under the provisions of Part 65 of this subchapter 
and upon request by the Administrator during the review of previously recognized structures.  The 
FEMA review will establish appropriate risk zone determinations for NFIP maps. 
	(b)	Design criteria.  For levees to be recognized, FEMA must receive evidence that 
adequate design, operation, and maintenance systems are in place to provide reasonable assurance 
of protection from the 100-year flood .  The following requirements must be met:
	(1)	Freeboard.  (i) Riverine levees must provide a minimum freeboard of 3 feet above 
the water-surface level of the 100-year flood, but they must be at least of such height that there is a 
90-percent conditional nonexceedance probability – referred to here as “assurance” – of containing 
the 100-year flood.  Paragraph (b)(1)(v) below defines and has references related to “assurance.”  
An additional 1 foot above the minimum is required within 100 feet on either side of structures (such 
as bridges) riverward of the levee, or wherever the flow is constricted.  An additional one-half foot 
above the minimum at the upstream end of the levee, tapering to not less than the minimum at the 
downstream end of the levee, is also required.
	(ii)	Occasionally, exceptions to the minimum riverine freeboard requirement described 
in Paragraph (b)(1)(i) of this section may be approved.  Appropriate engineering analyses that 
demonstrate adequate protection with a lesser freeboard must be submitted to support a request for 
such an exception.  The presented material must evaluate the uncertainty in the estimated BFE 
profile and include, but not be limited to, an assessment of the statistical confidence limits of the 
100-year discharge; changes in stage-discharge relationships; and the sources, potential, and 
magnitude of debris, sediment, and ice accumulation.  It must also show that the levee will remain 
structurally stable during the 100-year flood, when such additional loads are imposed.  Under no 
circumstances will a freeboard of less than 2 feet be accepted.  Uncertainty analysis based on these 
factors, which demonstrates a 95-percent assurance of containing the 100-year flood, is acceptable 
justification for the 2-foot minimum freeboard.
	(iii)	For coastal levees, the freeboard must be established at 1 foot above the height of 
the 1-percent wave or the maximum wave runup (whichever is greater) associated with the 100-
year stillwater surge elevation at the site.  The freeboard must at least be of such height that there is 
a 90-percent assurance of containing the 1-percent wave or the maximum wave runup (whichever 
is greater) associated with the 100-year stillwater surge elevation at the site.
	(iv)	Occasionally, exceptions to the minimum coastal levee freeboard requirement 
described in Paragraph (b)(1)(iii) of this section may be approved.  Appropriate engineering 
analyses that demonstrate adequate protection with a lesser freeboard must be submitted to support 
a request for such an exception.  The presented material must evaluate the uncertainty in the 
estimated 100-year flood loading conditions.  Particular emphasis must be placed on the effects that 
wave attack and overtopping will have on the stability of the levee.  Under no circumstances will a 
freeboard of less than 2 feet above the 100-year stillwater surge elevation be accepted.  Uncertainty 
analysis that demonstrates a 95-percent assurance of containing the 1-percent wave or the 
maximum wave runup (whichever is greater) associated with the 100-year stillwater surge elevation 
at the site is acceptable justification for the 2-foot minimum freeboard.
	(v)	“Assurance” is defined as the percentage of chance that floodwaters associated 
with the discharge having a 1-percent chance of being exceeded in any given year will not inundate 
any area landward of a levee system that would be inundated without the benefit of the levee 
system.  Assurance is a concept inherent in the USACE risk analysis framework as described in 
USACE manual ER 1110-2-101, entitled “Risk Analysis for Flood Damage Reduction Studies,” and 
USACE manual EM 1110-2-1619, entitled “Risk-based Analysis for Flood Damage Reduction 
Studies."
	(2)	Closures.  All openings must be equipped with closure devices that are structurally 
part of the system during operation and designed according to sound engineering practice.
	(3)	Embankment protection.  Engineering analyses must be submitted to demonstrate 
that no appreciable erosion of the levee embankment can be expected during the 100-year flood, as 
a result of either currents or waves, and that the anticipated erosion will not result in direct failure 
of the levee embankment or foundation or indirect failure through reduction of the seepage path and 
subsequent instability.  The factors to be addressed in such analyses include, but are not limited to:  
expected flow velocities (especially in constricted areas); expected wind and wave action; ice 
loading; the impact of debris; slope protection techniques; the duration of flooding at various stages 
and velocities; embankment and foundation materials; levee alignment, bends, and transitions; and 
levee side slopes.
	(4)	Embankment and foundation stability.  Engineering analyses that evaluate levee 
embankment stability must be submitted.  These analyses should evaluate the expected seepage 
during loading conditions associated with the 100-year flood and should demonstrate that seepage 
into or through the levee foundation and embankment will not jeopardize the stability of the 
embankment or foundation.  An alternative analysis demonstrating that the levee is designed and 
constructed for stability against loading conditions for Case IV as defined in the USACE manual 
entitled “Design and Construction of Levees” (EM 1110-2-1913, Chapter 6, Section II), may be 
used.  The factors that should be addressed in these analyses include depth of flooding, duration of 
flooding, embankment geometry and length of seepage path at critical locations, embankment and 
foundation materials, embankment compaction, penetrations, other design factors affecting seepage 
(such as drainage layers), and other design factors affecting embankment and foundation stability 
(such as berms).
	(5)	Settlement.  Engineering analyses that assess the potential and magnitude of future 
losses of freeboard as a result of levee settlement and demonstrate that freeboard will be maintained 
within the minimum standards set forth in Paragraph (b)(1) of this section must be submitted.  These 
analyses must address embankment loads, compressibility of embankment soils, compressibility of 
foundation soils, age of the levee system, and construction compaction methods.  In addition, a 
detailed settlement analysis using procedures such as those described in the USACE manual entitled 
“Soil Mechanics Design - Settlement Analysis” (EM 1100-2-1904) must be submitted.
	(6)	Interior drainage.  An analysis that identifies the source(s) of such flooding; the 
extent of the flooded area; and, if the average depth is greater than 1 foot, the water-surface 
elevation(s) of the 100-year flood must be submitted.  This analysis must be based on the joint 
probability of interior and exterior flooding and the capacity of equipment (such as drainage lines and 
pumps) that evacuates interior floodwaters.
	(7)	Other design criteria.  In unique situations, such as those where the levee system 
has a relatively high vulnerability, FEMA may require that other design criteria and analyses be 
submitted to show that the levees provide adequate protection.  In such situations, sound engineering 
practice will be the standard on which FEMA will base its determinations.  FEMA will also provide 
the rationale for requiring this additional information.
	(c)	Operation plans and criteria.  For a levee system to be recognized, the 
operational criteria must be as described below.  All closure devices or mechanical systems for 
internal drainage, whether manual or automatic, must be operated in accordance with an officially 
adopted operation manual.  The levee operator must provide a copy of this manual to FEMA when 
seeking levee or drainage system recognition or when the manual for a previously recognized 
system is revised in any manner.  All operations must be under the jurisdiction of a Federal or State 
agency, an agency created by Federal or State law, or an agency of a community participating in the 
NFIP.
	(1)	Closures.  Operation plans for closures must include the following:
	(i)	Documentation of the flood warning system, under the jurisdiction of Federal, State, 
or community officials, that will be used to trigger emergency operation activities and a 
demonstration that the flood warning time provided will be sufficient to complete all structure closure 
operations, including necessary sealing, before floodwaters reach the base of the closure
	(ii)	A formal plan of operation, including specific actions and assignments of 
responsibility by individual names or titles
	(iii)	Provisions for periodic operation, at not less than 1-year intervals, of the closure 
structure for testing and training purposes
	(2)	Interior drainage systems.  The interior drainage systems associated with levee 
systems often include storage areas, gravity,, outlets, pumping stations, or a combination thereof.  
These drainage systems will be recognized by FEMA on NFIP maps for flood protection purposes 
only if the following minimum criteria are included in the operation plan:
	(i)	Documentation of the flood warning system, under the jurisdiction of Federal, State, 
or community officials, that will be used to trigger emergency operation activities, and demonstration 
that the flood warning time is sufficient to permit the activation of mechanized portions of the 
drainage system
	(ii)	A formal plan of operation, including specific actions and assignments of 
responsibility by individual names or titles
	(iii)	Provision for manual backup for the activation of automatic systems
	(iv)	Provisions for periodic inspections of interior drainage systems and the periodic 
operation of any mechanized portions for testing and training purposes.  No more than 1 year shall 
elapse between either the inspections or the operations.
	(3)	Other operation plans and criteria.  Other operating plans and criteria may be 
required by FEMA to ensure that adequate protection is provided in specific situations.  In such 
cases, sound emergency management practice will be the standard upon which FEMA’s 
determinations will be based.
	(d)	Maintenance plans and criteria.  For FEMA to recognize levee systems as 
providing protection from the 100-year flood, the maintenance criteria must be as described herein.  
Levee systems must be maintained in accordance with an officially adopted maintenance plan, and a 
copy of this plan must be provided to FEMA by the owner of the levee system when recognition is 
being sought or when the plan for a previously recognized system is revised in any manner.  All 
maintenance activities must be under the jurisdiction of a Federal or State agency, an agency 
created by Federal or State law, or the agency of a community participating in the NFIP that must 
assume ultimate responsibility for maintenance.  This plan must document the formal procedure that 
ensures that the stability, height, and overall integrity of the levee and its associated structures and 
systems are maintained.  At a minimum, maintenance plans should specify the maintenance 
activities to be performed, the frequency of their performance, and the name or title of the person 
responsible for their performance.
	(e)	Residual risk and public safety.  The issues addressed here are focused on public 
safety during flood events exceeding the capacity of the levee system.  The components that must 
be addressed are the probability of capacity exceedance, the consequence of capacity exceedance, 
an examination of project features that address capacity exceedance, and emergency plans to 
ensure public safety in the event of a flood that exceeds the levee system capacity.
	(1)	Probability of capacity exceedance.  The threat to floodplain residents and 
businesses is best described by the probability of capacity exceedance.  The probability must be 
estimated based on information on flood flow and stage and associated uncertainties, the integrity of 
the levee embankment and associated structures and the potential failure probabilities, and an 
analysis of closure devices and other components.  The probability of capacity exceedance is to be 
expressed as Annual Exceedance Probability (AEP), as defined in USACE manual ER 1105-2-101.
	(2)	Consequence of capacity exceedance.  The general scope and nature of the 
impact on floodplain residents, businesses, critical infrastructure systems, and the environment will 
be assessed and reported.  The intent is not to produce a detailed impact analysis, but to assess the 
threat to floodplain occupants and to indicate the approximate numbers and demographics of 
residents, businesses, and disruptions that would likely occur from a capacity exceedance.  This 
information would clearly distinguish between floodplains that may experience slow, shallow flooding 
and those that may experience rapid, deep flooding.  It also would delineate between floodplains that 
have adequate routes and capacity for occupant evacuations and those that do not.  Finally, it would 
separate floodplains that, if flooded from a levee system failure, would or would not result in the 
crippling of a regional economy or have significant national economic impact.
	(3)	Project features for capacity exceedance.  Levee system projects will be 
expected to have means to accommodate possible capacity exceedance.  Where feasible and 
practical, systems will be designed and constructed to account for possible capacity exceedance.  
Therefore, if capacity exceedance results in a failure of the levee system, the failure will occur 
gradually and in a predictable manner.  Levee superiority is one physical means for such 
accommodation, and another is to harden sections to withstand overtopping (see USACE manual 
ER 1110-2-229, entitled “Overtopping of Flood Control Levees and Floodwalls”).  Documented 
evidence of accommodating capacity exceedance is required.
	(4)	Emergency response plan.  Communities with levee systems are required to have 
current (updated within 5 years) flood warning and emergency response plans that demonstrate that 
public safety from flood events that exceed levee system capacity has been planned for and that the 
plan has a high likelihood of being successful.  Emergency response plans will address the key 
issues of  flood threat recognition, warning dissemination, evacuation, and search and rescue.  
Documentation must be submitted to demonstrate that the plan will remain viable through an annual 
review of action plans and updating official contacts and their responsibilities.  Periodic testing of the 
plan must also be documented. 
	(f)	Certification requirements.  Data supporting a given levee system’s compliance 
with the structural requirements set forth in Paragraphs (b)(1) through (7) of this section must be 
certified by a registered professional engineer.  Certified as-built plans of the levee must also be 
submitted.  Certifications are subject to the definition given in §65.2 of this subchapter.  In lieu of 
these structural requirements, a Federal agency with responsibility for levee design may certify that 
the levee has been adequately designed and constructed to provide protection against the 100-year 
flood.


Revision 2 – Total Change 
	(a)	General.  For purposes of the NFIP, FEMA will only recognize in its flood hazard 
and risk mapping those levee and floodwall systems (hereafter referred to as “levee systems”) that 
meet, and continue to meet, minimum design, construction, operation, and maintenance standards 
consistent with the level of protection sought through the comprehensive floodplain management 
criteria established by §60.3 of this subchapter.  Accordingly, this section describes the types of 
information FEMA requires to recognize, on NFIP maps, that a levee system provides protection 
from the 100-year flood while concurrently recognizing the residual risk that continues to exist from 
the 100-year flood.  The community or other party seeking recognition of such a levee system must 
supply this information to FEMA at the time a flood risk study or restudy is conducted, when a map 
revision is sought on the basis of a levee system under the provisions of Part 65 of this subchapter, 
and upon request by the Administrator during the review of previously recognized structures.  The 
FEMA review will establish appropriate risk zone determinations for NFIP maps.
	(1)	Risk and uncertainty framework.  A risk analysis framework will be used to 
determine whether levees provide adequate protection from the 100-year flood.  Quantitative 
assessment of the uncertainty associated with key engineering elements of the levee protection 
system will be required.  These uncertainties will be formed into an analysis framework that 
measures whether the levee provides protection from the 100-year flood, referred to here as 
“assurance.”  Assurance is defined as the percentage of chance that floodwaters associated with 
the discharge having a 1-percent chance of being exceeded in any given year will not inundate areas 
landward of a levee system that would be inundated without the benefit of the levee system.  The 
risk analysis framework is described in USACE manual ER 1110-2-101, entitled “Risk Analysis for 
Flood Damage Reduction Studies,” and methods for performing such analysis are documented in 
USACE manual EM 1110-2-1619, entitled “Risk-based Analysis for Flood Damage Reduction 
Studies."
	(2)	New levees vs. existing or reevaluated levees.  For newly constructed levees that 
are undergoing analysis for certification determination, the primary emphasis will be on assessing the 
design criteria, and the key issue will be the levee height required to contain the 100-year flood with  
90-percent assurance.  Uncertainties in factors other than the 100-year flood stage are likely to be 
of less importance.  To evaluate existing levees not previously studied for certification, or to 
reevaluate existing levees that have not been reevaluated for some time, assessing the structural 
integrity of the levee in its constructed state will be the key issue.  In the risk and uncertainty 
framework, assessing existing levees will include an analysis of the design criteria, if known, and the 
likely integrity of the geotechnical and other structural features through development and analysis of 
elevation-failure probability functions that reflect the uncertainty inherent in characterizing the 
structural integrity of existing, and sometimes aged and aging, levee systems.  In this instance, the 
levee height to ensure a 90-percent assurance of containing the 100-year flood will not be the only 
determining factor; instead, the overall assurance that the levee system will contain the 100-year 
flood will govern.
	(b)	Design, construction, and maintenance.  For levees to be recognized by FEMA, 
the certifier must provide evidence that adequate design and construction standards were employed, 
and that operation and maintenance systems are in place.  This provides a reasonable and quantified 
assurance of protection from the 100-year flood.  The analysis required to demonstrate assurance 
will include an analysis of riverine and coastal 100-year flood stages and associated uncertainties, 
and the integrity of levee embankment and foundation structures, as quantified by levee elevation-
failure probability relationships.  These relationships will be formed into a risk analysis framework, 
and the assurance of protecting against the 100-year flood will be computed.  The overall, combined 
assurance of protecting against the 100-year flood must be a minimum of 90 percent. 
	(1)	Riverine and coastal 100-year flood stages and uncertainties.  
	(i)	Riverine 100-year flood stage and associated uncertainties are derived from 
frequency analysis of stage records, stage frequency developed from unsteady flow model analysis, 
or stage frequency developed from 100-year flood discharge and stage-flow modeling.  Also 
included in the uncertainty estimates will be the potential for sediment accumulation and debris and 
ice accumulation and blockage.  The resulting relationships are the 100-year flood flow frequency 
and stage rating with associated uncertainties, or “100-year flood stage and associated uncertainty.”
	(ii)	Coastal 100-year flood stage and associated uncertainties are the 1-percent wave 
or the maximum wave run-up (whichever is greater) associated with the 1-percent-annual-chance 
stillwater surge elevation at the site, and the associated uncertainties.  The resulting relationship is an 
elevation-exceedance probability relationship and associated uncertainty.
	(2)	Levee structural integrity and uncertainty.  
       (i)	Engineering analyses must be submitted to demonstrate that no appreciable erosion 
of the levee embankment can be expected during the 100-year flood as a result of either currents or 
waves, and that anticipated erosion is not likely to result in direct failure of the levee embankment or 
foundation or indirect failure through reduction of the seepage path and subsequent instability.  A 
quantitative assessment of the integrity of the levee from erosion forces for the full range of flood 
stages must be conducted.  A relationship depicting this assessment will define the probability of 
levee failure as a function of flood elevation.  The factors to be addressed in such analyses include, 
but are not limited to:  expected flow velocities (especially in constricted areas); expected wind and 
wave action; ice loading; impact of debris; slope protection techniques; duration of flooding at 
various stages and velocities; embankment and foundation materials; levee alignment, bends, and 
transitions; and levee side slopes.
	(ii)	Engineering analyses that evaluate levee embankment stability must be submitted.  
These analyses should evaluate the expected seepage during loading conditions associated with the 
100-year flood and associated uncertainty, and should demonstrate that seepage into or through the 
levee foundation and embankment will not jeopardize the stability of the embankment or foundation.  
An alternative analysis demonstrating that the levee is designed and constructed for stability against 
loading conditions for Case III or IV, depending on the specific circumstance, as defined in the 
USACE manual entitled “Design and Construction of Levees” (EM 1110-2-1913, Chapter 6, Section 
II), may be used.  A quantitative assessment of levee integrity from an embankment stability 
perspective must be made.  Embankment strength and seepage consequences for all flood stages 
should be assessed.  A relationship depicting this assessment will define the probability of levee 
failure as a function of flood elevation.  The factors to be addressed in the analyses include:  depth 
of flooding, duration of flooding, embankment geometry and length of seepage path at critical 
locations, embankment and foundation materials, embankment compaction, penetrations, other 
design factors affecting seepage (such as drainage layers), and other design factors affecting 
embankment and foundation stability (such as berms).  USACE manual ETL 1110-2-556, entitled 
“Risk Analysis in Geotechnical Engineering for Support of Planning Studies,” and USACE manual 
ETL 1110-2-547, entitled “Introduction to Probability and Reliability Methods in Geotechnical 
Engineering,” are useful references for this analysis.
	(iii)	Engineering analyses that evaluate floodwall/structure stability must be submitted.  
The analyses provided shall evaluate expected seepage during loading conditions associated with the 
100-year flood and associated uncertainty, and shall demonstrate that seepage into or through the 
floodwall foundation will not jeopardize foundation stability.  A quantitative assessment must be 
conducted to show the integrity of the floodwall structural integrity and the foundation stability during 
the full range of flood stages.  A relationship depicting this assessment will define the probability of 
levee failure as a function of flood elevation.  The factors to be addressed in the analyses include:  
depth of flooding, duration of flooding, floodwall geometry and strength, length of seepage path at 
critical locations, foundation materials, foundation preparation, other design factors affecting seepage 
(such as drainage layers), and other design factors affecting floodwall foundation stability (such as 
berms).
	(iv)	A composite levee structural integrity relationship shall be derived from combining 
the flood elevation ? levee failure relationships developed in  Paragraphs (b)(2)(i), (b)(2)(ii), and 
(b)(2)(iii) above for use in the overall assurance computation required in Paragraph (2)(b).
	(3)	Closures.  All openings must be provided with closure devices that are structural 
parts of the system during operation and designed according to sound engineering practice.  
Maintenance plans and annual test results of the operation plans for all closure structures must be 
submitted.
	(4)	Consolidation, settlement, and regional subsidence.  Engineering analyses that 
assess the potential and magnitude of future losses of levee crest elevation as a result of 
consolidation, settlement, or regional subsidence must be submitted.  The analysis must demonstrate 
that the required crest elevation will be maintained, or that plans exist for periodically raising levees 
to required heights over the expected life of the levee project.  This analysis must address 
embankment loads, compressibility of embankment soils, compressibility of foundation soils, age of 
the levee system, and construction compaction methods.  In addition, detailed settlement analysis 
using procedures such as those described in the USACE manual entitled  “Soil Mechanics Design - 
Settlement Analysis,” (EM 1100-2-1904) must be submitted.
	(5)	Interior drainage.  An analysis must be submitted that identifies the source(s) of 
such flooding; the extent of the flooded area; and, if the average depth is greater than 1 foot, the 
water-surface elevation(s) of the 100-year flood.  This analysis must be based on the coincidental 
probability of interior and exterior flooding and the capacity of equipment (such as drainage lines and 
pumps) for evacuating interior floodwaters.  See USACE manual EM 1110-2-1413, entitled 
“Hydrologic Analysis of Interior Areas,” for guidance on these studies. 
	(6)	Other design criteria.  In unique situations, such as those where the levee system 
has a relatively high vulnerability, FEMA may require that other design criteria and analyses be 
submitted to show that the levees provide adequate protection.  In such situations, sound engineering 
practice will be the standard upon which FEMA will base its determinations.  FEMA will also 
provide the rationale for requiring this additional information.
	(7)	Additional levee height.  The overall risk and uncertainty computation required in 
Paragraph (2)(b) will determine whether the levee height and structural integrity for the system 
being evaluated, taken together, equal or exceed the required 90-percent assurance.  For riverine 
levees, superiority of an additional 1-foot height is required within 100 feet on either side of key 
structures (such as bridges) riverward of the levee, or wherever the flow is constricted.  An 
additional one-half foot in height is required at the upstream end of the levee, tapering to not less 
than the levee height at the downstream end of the levee.
	(c)	Operation plans and criteria.  For a levee system to be recognized, the 
operational criteria must be as described below.  All closure devices or mechanical systems for 
internal drainage, whether manual or automatic, must be operated in accordance with an officially 
adopted operation manual.  The levee operator must provide a copy of the manual to FEMA when 
levee or drainage system recognition is being sought or when the manual for a previously recognized 
system is revised in any manner.  All operations must be under the jurisdiction of a Federal or State 
agency, an agency created by Federal or State law, or an agency of a community that participates in 
the NFIP.  An assessment must identify the likelihood of the successful operation of system 
components during a flood event, considering the availability of such critical resources as access to 
devices, labor, power supply, needed materials, and the operational readiness of the features.  The 
impact and consequence of unsuccessful operation must be determined and evaluated.
	(1)	Closures.  Operation plans for closures must include the following:
	(i)	Documentation of the flood warning system, under the jurisdiction of Federal, State, 
or community officials, that will be used to trigger emergency operation activities and a 
demonstration that the flood warning time is sufficient to complete all closure operations, including 
locating, accessing, and installing the closure structures, and the necessary sealing, before 
floodwaters reach the base of the closure
	(ii)	A formal plan of operation, including specific actions and assignments of 
responsibility by individual names or titles
	(iii)	Provisions for periodic operation, at not less than 1-year intervals, of the closure 
structure for testing and training purposes
	(2)	Interior drainage systems.  Interior drainage systems associated with levee 
systems usually include storage areas, gravity, outlets, pumping stations, or a combination thereof.  
These drainage systems will be recognized by FEMA on NFIP maps for flood protection purposes 
only if the following minimum criteria are included in the operation plan:
	(i)	Documentation of the flood warning system, under the jurisdiction of Federal, State, 
or community officials, that will be used to trigger emergency operation activities and a 
demonstration that the flood warning time is sufficient to activate the mechanized portions of the 
drainage system
	(ii)	A formal plan of operation, including specific actions and assignments of 
responsibility by individual names or titles
	(iii)	Provision for manual backup for the activation of automatic systems
	(iv)	Provisions for periodic inspection of interior drainage systems and periodic operation 
of any mechanized portions for testing and training purposes.  No more than 1 year shall elapse 
between either the inspections or the operations.
	(3)	Other operation plans and criteria.  FEMA may require other operating plans 
and criteria to ensure that adequate protection is provided in specific situations.  In such cases, 
sound emergency management practice will be the standard upon which FEMA bases its 
determinations.
	(d)	Maintenance plans and criteria.  For levee systems to be recognized as providing 
protection from the 100-year flood, the maintenance criteria must be as described herein.  Levee 
systems must be maintained in accordance with an officially adopted maintenance plan, and the 
owner of the levee system must provide a copy of this plan to FEMA when recognition is being 
sought or when the plan for a previously recognized system is revised in any manner.  All 
maintenance activities must be under the jurisdiction of a Federal or State agency, an agency 
created by Federal or State law, or an agency of a community participating in the NFIP that must 
assume ultimate responsibility for maintenance.  This plan must document the formal procedure that 
ensures that the stability, height, and overall integrity of the levee and its associated structures and 
systems are maintained.  At a minimum, maintenance plans shall specify the maintenance activities 
to be performed, the frequency of their performance, and the name or title of the person responsible 
for their performance.
	(e)	Residual risk and public safety.  The issues addressed here are focused on public 
safety during flood events that exceed the capacity of the levee system.  The components that must 
be addressed are probability of capacity exceedance, consequence of capacity exceedance, 
examination of project features that address capacity exceedance, and emergency plans to ensure 
public safety in the event of a flood that exceeds the levee system capacity
	(1)	Probability of capacity exceedance.  The threat to floodplain residents and 
businesses is best described by the probability of capacity exceedance.  The probability is to be 
estimated based on information compiled for flood flow and stage and associated uncertainties; 
levee embankment and integrity and potential failure probabilities of associated structures;, and 
operations analysis of closure devices and other components.  The probability of capacity 
exceedance is to be expressed as AEP, as defined in USACE manual ER 1105-2-101.
	(2)	Consequence of capacity exceedance.  The general scope and nature of the 
impact on floodplain residents, businesses, critical infrastructure systems, and the environment will 
be assessed and reported.  The intent is not to provide a detailed impact analysis, but to assess the 
threat to floodplain occupants and to indicate the approximate numbers and demographics of 
residents, businesses, and the disruptions that would likely occur from a capacity exceedance.  This 
information would clearly distinguish between floodplains that may experience slow, shallow flooding 
and those that may experience rapid, deep flooding.  It also would delineate between floodplains that 
have adequate routes and capacity for occupant evacuations and those that do not.  Finally, it would 
separate floodplains that, if flooded from a levee system failure, would or would not result in the 
crippling of a regional economy or have significant national economic impact.
	(3)	Project features for capacity exceedance.  Levee system projects will be 
expected to have features and other means to accommodate possible capacity exceedance.  Where 
feasible and practical, the system will be designed and constructed to account for capacity 
exceedance.  Therefore, if capacity exceedance results in failure of the levee system, the failure will 
occur gradually and in a predictable manner.  Levee superiority is one physical means for such 
accommodation; another is to harden sections to withstand overtopping (see USACE manual 
ER 1110-2-229, entitled “Overtopping of Flood Control Levees and Floodwalls”).  Documented 
evidence of considering and accommodating capacity exceedance is required.
	(4)	Emergency response plan.  Communities with levee systems are required to have 
current (updated within 5 years) flood warning and emergency response plans that demonstrate 
successful planning to safeguard the public against flood events that exceed levee system capacity.  
Emergency response plans will address the key issues of flood threat recognition, warning 
dissemination, evacuation, and search and rescue.  Documentation must be submitted to 
demonstrate that the plan will remain viable through an annual review of action plans and the 
updating of official contacts and their responsibilities.  Periodic testing of the plan must be 
documented.
	(f)	Certification requirements.  Data submitted to show that a given levee system 
complies with the structural requirements set forth in Paragraphs (b)(1) through (7) of this section 
must be certified by a registered professional engineer.  Certified as-built plans of the levee must 
also be submitted.  Certifications are subject to the definition given in §65.2 of this subchapter.  In 
lieu of these structural requirements, a Federal agency with the responsibility for levee design may 
certify that the levee has been adequately designed and constructed to provide protection against the 
100-year flood.


Appendix D.	Public Awareness and Outreach 
Approach
As indicated in Section 8 of this report, as FEMA moves forward with the development and 
implementation of levee-related policy, regulatory, and procedural changes, it must also develop and 
implement a public awareness and outreach strategy that will improve public officials’ and citizens’ 
awareness and understanding of levee-associated hazards and risks.  To do this, FEMA will need to 
work with its Federal, State, and local partners—both governmental and nongovernmental—to build 
on these partners’ successes, avoid their mistakes, and lead the development of a comprehensive, 
synergistic strategy that can and will be implemented consistently everywhere levee structures and 
systems are located.  Some initial steps to developing such a strategy include:
*	Definition of Roles and Responsibilities – To implement the public awareness and 
outreach approach effectively, many people will need to be involved, and the roles and 
responsibilities of those people will need to be clarified as soon as possible.  In addition 
to establishing roles and responsibilities for FEMA Headquarters and Regional Office 
staff—including Mitigation, Legislative Affairs, Intergovernmental Affairs, Public Affairs, 
and External Affairs—and FEMA contractors (including the contractor leading the FEMA 
FloodSmart campaign), roles and responsibilities will need to be established for the following:
?	Federal agencies involved in the construction and maintenance of levees and levee 
systems
?	State agencies involved in the construction and maintenance of levees and levee 
systems
?	Regional and local agencies involved in the construction and maintenance of levees and 
levee systems
?	State NFIP Coordinators
?	Nongovernmental organizations such as ASFPM, NAFSMA, and the American Society 
of Civil Engineers 
?	National and local media
*	Message Content and Format – To improve stakeholders’ understanding and compliance 
with current and future FEMA policies, regulations, and procedures, FEMA should provide 
them with appropriate information in a straightforward, easy-to-understand, question-and-
answer format.  This information could be provided together in pamphlet form or as a series 
of messages distributed separately as fact sheets or informational flyers.  The information 
must be complete, audience targeted, and delivered in a timely manner.

Under the leadership of the FEMA Mitigation Division Director or his designee, a work group 
composed of public awareness and outrach specialists from FEMA Headquarters, FEMA Regional 
Offices, FEMA contractors, other Federal agencies, State agencies, and nongovernmental 
organizations should develop a comprehensive list of questions that need to be answered.  The 
questions, and the answers to those questions, would form the basis for the key messages that are to 
be delivered.  Depending on the breadth and depth of the questions and answers, materials may 
need to be developed for both general and specific audiences so that those groups will see the 
impact on, and benefit to, them. 
Some of the questions to be answered quickly, for those communities with levees for which flood 
map updates are already underway, are listed below. 
*	General Levee Information
?	What are levees?
?	What threats and risks are associated with levees?
?	What materials are used to build levees?
?	Why are levees constructed?
?	What level of safety do levees provide?
?	Are people who live near a levee safe?
?	What will happen if the levee does not perform as designed?
?	Where can people go to learn more about the levees in their community?
?	Why is it important to understand how the levee operates?
?	What are the benefits of the levees?

*	Levee Construction and Maintenance Requirements
?	Who is responsible for maintaining the levees?
?	What does levee maintenance mean?
?	What are the Federal requirements for the construction and maintenance of levees?
?	What are the State requirements for the construction and maintenance of levees?
?	What are the local requirements for the construction and maintenance of levees?
?	What can families do to make their homes and themselves safer in a levee-protected 
area?
?	Whom should people contact if they have concerns about the levees near my home or 
business?
?	What can individuals do about levees?

*	FEMA Mapping Practices
?	Why is it important to accurately portray the flood hazards in areas affected by levees?
?	For what reasons did FEMA institute its current policies, regulations, and procedures 
regarding the evaluation of levees and the mapping of levee-affected areas?
?	How do interested parties find out if the levees in their community are affected?
?	Where in the NFIP regulations are the requirements for the evaluation of levees and 
the mapping of levee-affected areas found? 
?	Where in the Guidelines and Specifications for Flood Hazard Mapping Partners 
are the requirements for the evaluation of levees and the mapping of levee-affected 
areas found?
?	What changes will be made to the existing (effective) flood maps?
?	When will the changes to the existing flood maps be made?
?	How do interested parties find out if their community, property, etc., is affected by the 
changes to the flood map?
?	What effect(s) will the changes have on floodplain management in the affected areas?
?	What effect(s) will the changes have on flood insurance purchase requirements in the 
affected areas?
?	What information must be submitted to refute the changes made to the flood map(s) in 
the affected areas?
?	Who should prepare required supporting data and documentation to request that levees 
be credited with providing 1-percent-annual-chance (100-year) flood protection?
?	How are the required supporting data and documentation to be submitted to FEMA?
?	How will FEMA respond to requests to have levees credited with providing 100-year 
flood protection?
?	What kind of support is available to communities who do not have resources to collect 
and submit the required data?
?	Where can interested parties learn more about the NFIP regulations and the 
Guidelines and Specifications?
?	What do affected citizens ? property owners, builders, developers, and others – need to 
know and do?

If changes to levee-related policies, regulations, and procedures are made in the future, this same 
work group or a similar group would need to develop additional questions and answers. 
Message Delivery Vehicles
The FEMA public awareness and outreach approach should, to the extent possible, build on 
relationships already established as part of other Map Mod, risk insurance, and risk reduction 
activities; leverage existing communication vehicles; and develop new or alternative communication 
vehicles to provide various audiences with the clear, vital messages that are required.  Some existing 
and new communication vehicles that can be developed with a reasonable level of funding are 
summarized below.
*	Existing Communication Vehicles:
?	A Web page dedicated to the evaluation and mapping of levees should be posted on the 
FEMA Flood Hazard Mapping Web site and should be linked to the home page of that 
site.  The levee-dedicated Web page should have content similar to that of other 
important initiatives, such as the implementation of requirements for the use of future-
conditions hydrology and the implementation of the consolidated Guidelines and 
Specifications for Flood Hazard Mapping Partners.  Like those Web pages, the 
levee Web page should have a link for registering to receive levee-related e-mail 
messages from FEMA and should include the “Ask a Map Specialist” e-mail link and 
the FEMA Map Assistance Center toll-free number for interested parties with 
questions.  This will enable stakeholders and other interested parties to obtain accurate 
and appropriate information at any time.  Once the Web pages have been posted, 
FEMA could post information on the Map Service Center (MSC) Web page and on the 
main page of the Mapping Information Platform to encourage map users and active 
participants in the mapping process to visit the levee-dedicated Web page and learn 
more about levees.
?	Enclosures in e-mail message(s) to recipients of Map Mod messages and 
announcements could be distributed using the Lyris software vehicle that is already 
used for other map modernization announcements.  FEMA already distributes Map 
Mod messages regularly using Lyris software.  FEMA would need to update its 
database with the names and addresses of community officials and other stakeholders 
who should receive levee-related messages.  The messages could forward the 
materials FEMA develops or direct the recipients to the levee-dedicated Web page.
?	Enclosures could be sent with standard and nonstandard correspondence about topics 
other than levees that are sent to community officials and other stakeholders involved 
directly and indirectly in flood map updates.  FEMA regularly communicates with 
community officials and other stakeholders through standard and nonstandard 
correspondence regarding Letters of Map Amendment (LOMAs), Letters of Map 
Revision Based on Fill (LOMR-Fs), and Letters of Map Revision (LOMRs).  Along 
with the LOMA, LOMR-F, and LOMR correspondence, FEMA could forward levee-
related question-and-answer materials as unreferenced enclosures or provide materials 
that direct the recipients to the levee-dedicated Web page to learn more.  The FEMA 
MSC contractor also regularly distributes printed materials to various stakeholders.  
Levee-related informational materials could be distributed by the MSC contractor staff.
?	PowerPoint presentation(s) could be prepared for FEMA Headquarters and Regional 
Office management and staff to use at briefings for oversight groups, community 
meetings, and stakeholder conferences.  FEMA Headquarters and Regional Office 
management and staff have numerous opportunities to meet with groups of 
stakeholders, whether during community meetings, Community Assistance Visits, 
national and regional stakeholder conferences and meetings, or briefings with 
congressional delegations.  To facilitate consistent and clear communication on levee 
policy, regulations, and procedures, it would be very beneficial for presenters to have 
and use a well-vetted PowerPoint or DVD presentation.  FEMA could also provide this 
presentation to CTPs, State NFIP Coordinators, and others who may meet with groups 
of stakeholders without FEMA staff being in attendance.
?	Toolkits of information about flood insurance and map changes available for 
communities could be placed on the levee-dedicated Web site and on the 
floodsmart.gov Website 

*	New Communication Vehicles:
?	An informational letter could confirm to community officials (specifically, Chief 
Executive Officers (CEOs) and floodplain administrators) that levees do exist in their 
communities and could document what FEMA plans to do and the actions the 
community must take.  A significant amount of time and effort will likely be required for 
communities to obtain and submit the required documentation to show that a levee 
provides 1-percent-annual-chance or greater flood protection.  Therefore, using the 
sequencing information in the Multi-Year Flood Hazard Identification Plan and available 
information on the locations of levees as a guide, FEMA should consider sending 
informational letters to communities for which they already have or will be initiating a 
flood data update in 2006.  If the levee-dedicated Web page can be set up first, the 
letter could direct the CEO, floodplain administrator, and others to visit the site; if it is 
not available, the letter would forward whatever question-and-answer materials are 
available at the time.  It is not recommended that FEMA immediately send such letters 
to NFIP-participating communities with levees, if the flood data updates have not been 
initiated or will be initiated in 2007 or beyond.  Sequencing and schedules could change, 
and community CEOs and floodplain administrators may not be able or motivated to act 
when an update is more than a year in the future.
?	A pamphlet could explain FEMA policy, regulatory, and procedural requirements 
regarding levee evaluation and mapping and explain where more information and 
assistance can be obtained.  As mentioned earlier, the recommended pamphlet would 
present information in question-and-answer format and could be distributed to 
stakeholders as an enclosure to standard and nonstandard correspondence.  If the 
pamphlet were to be assigned a document number, FEMA could also have the 
pamphlet produced in large volumes by its Printing and Publications Branch or by the 
U.S. Government Printing Office.
?	A tutorial that provides a step-by-step explanation of the levee protection evaluation 
processes could be developed.  As a means of explaining these processes, FEMA 
should develop a tutorial, similar to the one made to explain the CTP program to 
potentially interested parties and the tutorials on the FEMA Flood Hazard Mapping 
Web site.  This tutorial would guide community CEOs and floodplain administrators 
through both processes and walk them through a decision-making approach so that they 
may take the appropriate action regarding levees in their communities.
?	Produce print or multimedia materials that put levee safety in context for nontechnical 
audiences.
?	Use the FIS report to expand on issues related to the history of the levees, relative 
protection provided by the levees and similar risk reduction systems, the inherent risk in 
building residential and nonresidential structures on the landward side of these systems, 
and alternative floodplain development practices that could be considered in levee 
affected areas.  

*	Targeted Audiences – It is critical that FEMA, in implementing this public awareness and 
outreach campaign, should engage both public- and private-sector audiences.  FEMA should 
develop a delivery strategy for each of these groups, as the messages may vary somewhat.  
One proposed approach has been documented already in a draft report entitled “FEMA 
Levee Policy Change Implementation:  Proposed Public Awareness Approach,” dated 
February 2006. 
*	The following are the public-sector audiences with whom FEMA should communicate:
?	Federal agencies that are not involved in the delivery of messages
?	Mapping Coalition members that are not involved in the delivery of messages
?	State NFIP Coordinators and other State agencies not involved in the delivery of 
messages
?	Regional entities not involved in the delivery of messages
?	Community officials

*	The following are the categories of private-sector stakeholder groups with whom FEMA 
should communicate: 
?	Engineers and surveyors
?	Construction, development, and real estate companies
?	Lending institutions and flood zone determination companies
?	Insurance companies and agents
?	Small business owners and homeowners

*	A detailed list of the organizations and individuals in each of the public- and private-sector 
stakeholders is provided in Appendix A of the previously referenced February 2006 draft 
report.

Measuring Success of Public Awareness and Outreach Activities
To measure the success of the public awareness and outreach activities described in this Appendix, 
FEMA Headquarters, FEMA Regional Offices, FEMA partners, and the FEMA contractor staff 
involved in these activities must be aware of potential roadblocks so that their impact may be 
avoided or minimized.  The staff involved also should collect and assess feedback from 
stakeholders.
*	Potential Roadblocks – Some of the roadblocks that may hinder the successful fulfillment of 
the public awareness and outreach campaign are listed below.  FEMA Headquarters and 
Regional Office staff should develop a comprehensive list through consultation with 
partners and contractors.  The staff involved in this campaign should monitor 
communication activities and notify the FEMA leadership if these roadblocks come to 
fruition and will have a negative impact on the public awareness and outreach campaign:
?	Federal agency committee members do not disseminate information to their 
headquarters and district office staff members.
?	Federal agency Webmasters are unable or unwilling to post information on their Web 
sites.
?	FEMA is not able to meet with the full membership of the Mapping Coalition.
?	Mapping Coalition members are unable to identify points of contact for the professional 
associations they represent.
?	Professional associations are unable to include levee-related messages in routine 
newsletters, e-mail messages, or other routine communication materials sent to 
members.
?	The MSC contractor is unable to distribute hard copies of levee-related messages along 
with printed copies of flood maps and reports.
?	Technical problems with Lyris software cause delays in dissemination of levee-related 
e-mail messages or make this approach cost prohibitive.
?	FEMA insurance specialists and the NFIP Bureau and Statisticial Agent are unable to 
distribute levee-related messages along with other information sent to insurance 
companies and agents, or at training sessions.
?	State agencies, regional entities, and community officials are unable or unwilling to 
make levee-related messages available to the people they serve.
?	FEMA representatives do not attend national stakeholder conferences.
?	Association points-of-contact are not able to distribute levee-related messages at 
national and regional stakeholder conferences that FEMA does not attend. 
?	FEMA staff are unable to carry out the public awareness and outreach activities, and 
FEMA does not have sufficient funding for FEMA contractors to carry out these 
activities.

*	Feedback Collection Mechanisms – FEMA should collect feedback on the effectiveness of 
the public awareness and outreach campaign by tracking: 
?	Number and content of incoming levee-related e-mails submitted through the “E-Mail a 
Map Specialist” page on the FEMA Web site
?	Number and source of comments, questions, and suggestions made by FEMA staff and 
FEMA contractor staff at regular coordination meetings (e.g., FEMA Headquarters 
“Map Mod conference calls” with FEMA Regional Offices)
?	Number and content of incoming levee-related calls to the FEMA Map Assistance 
Center
?	Number and content of inquiries received from congressional delegations
?	Number and source of comments, questions, and suggestions made by attendees at 
national and regional stakeholder conferences or training sessions attended by FEMA 
representatives
?	Number of subscribers reached through the Lyris e-mail notification
?	Number of visits to the levee Web page on the FEMA Flood Hazard Mapping Web site
?	Number of requests for FEMA-developed outreach materials and templates

Based on the collected feedback, FEMA should consider refining the public awareness and outreach 
materials developed or the approach taken to delivering those messages.



Appendix E.	Levee Database Framework Design 
Recommendations
Overall Recommendations
The following overall recommendations are proposed to develop the framework for a levee 
inventory and database:
*	Capture levee centerline location within a GIS framework.
*	Come to an agreement among Federal agencies on a common vocabulary that defines levees 
and their characteristics.
*	Include enough levee characteristics and attributes to permit a high-level analysis of mapped 
areas shown as providing protection, levee certification status, and the risks associated with 
levee failure.

Each is discussed in greater detail below.
The framework should be geospatial.  The levee database should be a geospatially based dataset.  
The advantages of a spatially oriented dataset are:
*	It answers the basic question of where levees are located.
*	It provides a spatially oriented dataset that allows levees to be depicted on a map with other 
data such as flooding sources, drainage basins, USACE projects, FEMA communities, 
counties, FIRM panels, DFIRM datasets where available, congressional and assembly 
districts, etc.
*	It permits the levee data to be incorporated into some hydrologic and hydraulic data models.
*	It allows levees to be used in conjunction with other GIS datasets to answer spatial queries, 
such as in which congressional district the levee is located.  This aspect also eliminates the 
need to capture elements of other datasets as attributes of the levee entity, thereby reducing 
the amount of data that needs to be stored with the levee entity and streamlining data 
maintenance.
*	The GIS layer, if positionally accurate, could be used as part of the official FEMA DFIRM 
database in the S_Gen_Struct layer, when the DFIRM is created.

Establish a Common Vocabulary
*	It is important that there be a common vocabulary to describe the entities and attributes that 
will make up a levee database.  The various Federal agencies have different definitions for 
flood protection and risk and apply different procedures to levee certification, which may 
also be accomplished by nongovernment professional engineers.  Documenting the data 
models or schemas will provide a foundation for the different interested parties to understand 
the information being captured and how it may benefit them.
*	To establish this vocabulary, it is helpful to define the entities and attributes for the database 
and represent them in an entity-relationship (E-R) diagram.  An E-R diagram provides a 
graphical representation of the data model and schema and allows easy identification of the 
connections between different entities.  It will also assist to define cardinality between the 
entities (i.e., where there are one-to-one, one-to-many, and many-to-many relationships). 
*	It is equally important that a data dictionary be created to identify the attributes being 
captured for each entity, how they are captured, and what appropriate vocabulary control 
mechanisms are in place to ensure data quality.  The separate levee database initiatives 
documented in this report have different purposes but also areas of consistency.  The data 
dictionaries will assist in getting all parties “on the same sheet.”
*	Before developing a data model, the essential elements of the database must be defined and 
used consistently.  To some extent, the definitions of these elements are dependent on the 
ultimate purpose of the database and how it will be used.  These definitions then are 
reflected in the data model.  The following recommendations are offered as points of 
discussion about these primitives.
?	Defining a Levee – A levee is a manmade structure, usually an earthen embankment, 
designed and constructed in accordance with sound engineering practices to contain, 
control, or divert the flow of water so as to provide protection from temporary flooding.  
Each unique levee is a continuous, unbroken segment that has a defined beginning and 
end point.  Characteristics such as ownership, freeboard, and type of construction may 
change along the levee, but if the levee is contiguous, then it is considered a single 
levee. 
?	Defining a Levee System – A levee system is a flood protection system that consists of 
a levee or levees and associated structures, such as closure and drainage devices, 
floodwalls, and natural topography, that are constructed and operated in accordance 
with sound engineering practices.  Failure at any one point of the levee system will 
result in the flooding of the area on the landward side of the system.  One levee system 
is separated by another levee system by flooding sources and topography.  A levee 
system is unique if a failure within that system does not affect another levee system.
?	Adjacent Floodprone Areas – Different terms are used to describe potential flooding on 
either side of the levee – inward and outward, along and behind, right bank and left 
bank, protected and unprotected.  Because some levees could completely enclose an 
area, these terms can be confusing.  It is recommended that the term “waterside” be 
used for the area parallel to the levee that contains the flood source and “landside” for 
the area parallel to the levee that may be protected.
?	Flood Protection – Levees have been built to provide varying degrees of protection (for 
different storm events, different land uses on the landside of the levee, etc.).  For the 
purposes of FEMA’s levee database, all the requirements of 44 CFR 65.10 would have 
to be met before the levee could definitively be said to provide protection.  Upon 
meeting the CFR criteria, the landside area of the levee can receive a flood zone 
designation that classifies it as outside the SFHA (X, X (shaded), B, or C).  
?	Certification – Certification should represent a levee that has been certified by an 
appropriate governing agency to meet all the requirements of 44 CFR 65.10.

Capture Levee Characteristics and Attributes Needed for Analysis
The following levee characteristics should be included in the levee database framework.  These 
characteristics are needed to perform a high-level analysis of levee protection status, certification 
status, and risk.
*	Ownership Information –Because the owner is generally charged with maintenance and 
upkeep of the levee, the owning entity, whether public or private, should be identified, along 
with a contact person within the entity.
*	Flood Protection Status – Levees that are shown as providing some level of protection are 
typically identified on a FEMA FIRM as Zone X (no SFHA), Zone X (shaded) (within the 
500-year flood event), and their corresponding legacy zone designations of C (no SFHA) and 
B (within the 500-year flood event).  In addition, it would be useful to identify where Zone D 
(undetermined) exists on the landside of levees as well.
*	Another important attribute to capture in this category would be the flood zone designations 
on the waterside of levees.  In many cases, the designations will be Zone A (100-year flood 
event), a Zone A designation with BFEs (e.g., AE, AH, AO), or the coastal flood 
designations of Zones V and VE.  Identifying the zone designation on the waterside of 
levees will be useful in determining where detailed studies have been performed and where 
BFEs exist that will aid in freeboard analysis.
*	Certification Status – Certification should represent a levee that has been certified by an 
appropriate governing agency to meet all the requirements of 44 CFR 65.10.  Some levees 
were certified before 44 CFR 65.10 was enacted.  It would be beneficial to note the 
locations of those levees but to designate them as not in conformance with the 44 CFR 65.10 
criteria.  It also would be beneficial to identify whether certifications are still valid (i.e., 
whether those levees with a current accreditation are based on professionally verified 
technical information).  Problems such as seepage or the scouring of levee sidewalls may 
have occurred recently on a levee that had been certified to meet the CFR criteria.
*	Risk Associated With Failure – Levees were designed and built to protect various land uses, 
from urban and suburban areas to agricultural fields.  In any sort of high-level levee analysis, 
it is important to know which levee systems, levees, or portions of levees protect the areas 
with the greatest risk of life and property losses from a levee failure.  Risk can be identified 
many different ways (e.g., people, property values, insurance valuation), but a good measure 
of risk is one of the population density adjacent to the levee.



Appendix F.	FIRM Map Zone Designations
FIRM Map Zone Designations (source:  FEMA)
Zone A.  Zone A is the flood insurance rate zone that corresponds to the 100-year floodplains that 
are determined in the FIS by approximate methods.  Because detailed hydraulic analyses are not 
performed for such areas, no 100-year flood elevations or depths are shown within this zone.  
Mandatory flood insurance purchase requirements apply.
Zone AE and A1-A30.  Zones AE and A1-A30 are the flood insurance rate zones that correspond 
to the 100-year floodplains that are determined in the FIS by detailed methods.  In most instances, 
100-year flood elevations derived from the detailed hydraulic analyses are shown at selected 
intervals within this zone.  Mandatory flood insurance purchase requirements apply.
Zone AH.  Zone AH is the flood insurance rate zone that corresponds to the areas of 100-year 
shallow flooding with a constant water-surface elevation (usually areas of ponding) where average 
depths are between 1 and 3 feet.  The BFEs derived from the detailed hydraulic analyses are shown 
at selected intervals within this zone.  Mandatory flood insurance purchase requirements apply.
Zone AO.  Zone AO is the flood insurance rate zone that corresponds to the areas of 100-year 
shallow flooding (usually sheet flow on sloping terrain) where average depths are between 1 and 
3 feet.  The depth should be averaged along the cross section and then along the direction of flow to 
determine the extent of the zone.  Average flood depths derived from the detailed hydraulic analyses 
are shown within this zone.  In addition, alluvial fan flood hazards are shown as Zone AO on the 
FIRM.  Mandatory flood insurance purchase requirements apply.
Zone AR.  Zone AR is the flood insurance rate zone used to depict areas protected from flood 
hazards by flood-control structures, such as a levee, that are being restored.  FEMA will consider 
using the Zone AR designation for a community if the flood protection system has been deemed 
restorable by a Federal agency in consultation with a local project sponsor; a minimum level of flood 
protection is still provided to the community by the system; and restoration of the flood protection 
system is scheduled to begin within a designated time period and in accordance with a progress plan 
negotiated between the community and FEMA.  Mandatory purchase requirements for flood 
insurance will apply in Zone AR, but the rate will not exceed the rate for unnumbered A zones if the 
structure is built in compliance with Zone AR floodplain management regulations.
For floodplain management in AR zones, elevation is not required for improvements to existing 
structures. However, for new construction, the structure must be elevated (or floodproofed for 
nonresidential structures) such that the lowest floor, including basement, is a maximum of 3 feet 
above the highest adjacent existing grade if the depth of the BFE does not exceed 5 feet at the 
proposed development site.  For infill sites, rehabilitation of existing structures, or redevelopment of 
previously developed areas, a 3-foot elevation requirement is in effect, regardless of the depth of the 
BFE at the project site.
The Zone AR designation will be removed, and the restored flood-control system will be shown as 
providing protection from the 100-year flood on the NFIP map, when the restoration project is 
completed and all the necessary data is submitted to FEMA.
Zone A99.  Zone A99 is the flood insurance rate zone that corresponds to areas of the 100-year 
floodplains that will be protected by a Federal flood protection system where construction has 
reached specified statutory milestones.  No BFEs or depths are shown within this zone.  Mandatory 
flood insurance purchase requirements apply.
Zone D.  The Zone D designation on NFIP maps is used for areas where there are possible but 
undetermined flood hazards.  In areas designated as Zone D, no analysis of flood hazards has been 
conducted.  Mandatory flood insurance purchase requirements do not apply, but coverage is 
available.  The flood insurance rates for properties in Zone D are commensurate with the 
uncertainty of the flood risk.
Zone V.  Zone V is the flood insurance rate zone that corresponds to the 100-year coastal 
floodplains that have additional hazards associated with storm waves.  Because approximate 
hydraulic analyses are performed for such areas, no BFEs are shown within this zone.  Mandatory 
flood insurance purchase requirements apply.
Zone VE and V1-30.  Zone VE and V1-V30 are the flood insurance rate zones that corresponds to 
the 100-year coastal floodplains that have additional hazards associated with storm waves.  BFEs 
derived from detailed hydraulic analyses are shown at selected intervals within this zone.  
Mandatory flood insurance purchase requirements apply.
Zones B, C, and X.  Zones B, C, and X are the flood insurance rate zones that correspond to areas 
outside the 100-year floodplains, areas of 100-year sheet flow flooding where average depths are 
less than 1 foot, areas of 100-year stream flooding where the contributing drainage area is less than 
1 square mile, or areas protected from the 100-year flood by levees.  No BFEs or depths are shown 
within these zones.  Zone X (shaded) is defined as areas of 500-year floods, areas of 100-year 
floods with depths less than 1 foot or with a drainage area less than 1 square mile, and areas 
protected by levees from the 100-year flood.


Appendix G.	List of Acronyms
AEP 					Annual Exceedance Probability
ASFPM				Association of State Floodplain Managers

BFEs					Base Flood Elevation

CEO					Chief Executive Officer
CTPs					Community Technical Partners

DFIRM					Digital Flood Insurance Rate Map
DWR 					California Department of Water Resources

E-R					entity-relationship
ERDC 					Engineer Research and Development Center

FEMA					Federal Emergency Management Agency
FHBM					Flood Hazard Boundary Map
FIA 					Federal Insurance Administration
FIRM					Flood Insurance Rate Map
FIS					Flood Insurance Study
FLIS 					FEMA Levee Inventory System

GIS 					Geographic Information System

H&H 					hydrologic and hydraulic
HEC-FAA
HFAWG 				Hydrologic Frequency Analysis Work Group
HUD 	U.S. Department of Housing and 
  Urban Development

LOMA					Letter of Map Amendment
LOMR					Letter of Map Revision
LOMR-F				Letter of Map Revision Based On Fill

Map Mod				Flood Map Modernization
MCC					Mapping Coordination Contractor
MSC 					Map Service Center

NAFSMA				National Association of Flood and 
         Stormwater Management Agencies
NAHB 					National Association of Homebuilders
NED 					national economic development
NFIP					National Flood Insurance Program
NOAA					National Oceanic and Atmospheric Administration
NRC 					National Research Council
NRCS 					Natural Resources Conservation Service
NSP					National Service Provider
NWS					National Weather Service
OMB					Office of Management and Budget

P&G 					Principles and Guidelines

R&D					research and development

SDSFIE				Special Data Standards for Facilities, Infrastructure, 
					  and Environment
SFHA					Special Flood Hazard Area
SPF 					Standard Project Flood

USACE				U.S. Army Corps of Engineers
USGS					U.S. Geological Survey


Appendix H.	References
Interagency Advisory Committee on Water Data, Hydrology Subcommittee.  Guidelines for 
Determining Flood-flow Frequency:  Bulletin 17B.  U.S. Department of Interior, Geological 
Survey, Office of Water Data Coordination.  Reston, Virginia, 1982.  183 pp.

Thomas, W.O., Jr., Lumb, A.M., Flynn, K.M., and Kirby, W.H.  Users Manual for Program 
PEAKFQ, Annual Flood Frequency Analysis Using Bulletin 17B Guidelines.  Water Resources 
Investigations Report.  U.S. Department of Interior, Geological Survey, Office of Surface Water.  
Reston, Virginia, 1998.  96 pp.

U.S. Department of Army, Corps of Engineers.  “Engineering and Design, Hydrologic Analysis of 
Interior Areas,” Engineer Manual 1110-2-1413.  CECS-EH.  January 1987.

U.S. Department of Army, Corps of Engineers, Hydrologic Engineering Center.  “HEC-FFA, Flood 
Frequency Analysis:  User’s Manual.”  CPD-13.  Davis, California, 1992.  79 pp.

U.S. Department of Army, Corps of Engineers, Hydrologic Engineering Center.  “Hydrologic 
Frequency Analysis,” Engineer Manual 1110-2-1415.  Davis, California, March 1993.

U.S. Department of Army, Corps of Engineers.  “Levee Owner’s Manual for Non-Federal Flood 
Control Works:  The Rehabilitation and Inspection Program, Public Law 84-99.”  March 2006.

U.S. Water Resources Council.  Economic and Environmental Principles and Guidelines for 
Water and Related Land Resources Implementation Studies.  Washington, D.C., 1983.



  Figures are not available on the percentage actually protected by levees.
  The 100-year flood is equivalent to the terms 1-percent-annual-chance flood, FEMA base flood, and base 
flood.
  Communities must provide interior drainage of areas behind levees.  When the drainage system will not 
provide adequate removal of storm waters, the community must identify areas that may flood as a result of 
inadequate drainage.  These areas may be designated as Special Flood Hazard Areas (SFHAs) and require 
application of land use regulations within the interior SFHAs.  
  On approval of levee certification documentation prepared by a professional engineer or an appropriate 
federal agency, FEMA will recognize the levee as providing protection against the base flood.  When the 
levee no longer provides the specified protection, it is considered to be decertified and the recognition is 
withdrawn.
  Flood risk is the product of the probability of occurrence of a flood and the consequences of that flood.  
Residual risk is the portion of risk that remains after a flood damage reduction structure  has been built. Risk 
remains because of the possibility that the capacity design level of protection for the structure is exceeded by 
a flood event that the structure fails and/or there are problems with the interior drainage.
  An explanation of zone definitions is provided in Appendix E.
  The U.S. Army Corps of Engineers is currently developing a risk assessment system that will be coordinated 
among Federal agencies.
  As noted earlier, levee owners or sponsors certify that levees meet FEMA standards (44 CFR 65.10).  If the 
certification information is acceptable, FEMA recognizes (or accredits) on NFIP maps that a levee system 
provides protection from the base flood.
  Statistics are not available for the percentage of the population actually protected by levees.
  The 100-year flood is equivalent to the terms 1-percent-annual-chance flood, FEMA base flood, and base 
flood.
  Most NRCS levees are designed to provide 4 percent (25-year) protection to support agricultural use of the 
land.
  On approval of levee certification documentation prepared by a professional engineer or an appropriate 
federal agency, FEMA will recognize the levee as providing protection against the base flood.  When the 
levee no longer provides the specified protection, it is considered to be decertified and the recognition is 
withdrawn.
  The term “temporary flooding” indicates that levees provide protection against temporary water level rises.  
When water is against a linear structure on a permanent basis as part of dam or lock system, it is normally 
referred to as a dike or a component of the dam and not as a levee.  There are cases, however, where these 
structures have been labeled levees. 
  Freeboard is intended to account for uncertainty in establishing the design water surface elevation that 
results from uncertain flow estimates and hydraulic conveyance.  Factors that can be estimated and accounted 
for should not be relegated to freeboard.  Accounting for such as effects as future watershed development (if 
permitted), bridge impairments, and wave action should be estimated and included in the design water surface 
elevation.

  The cited USACE Manuals are being revised or will be in the near future.
  Consideration could be given to including in the FIS issues related to the history of the levees, relative 
protection provided by the levees, and similar risk reduction systems, the inherent risk in building residential 
and non-residential structures on the landward side of these systems, and alternative floodplain development 
practices that could be considered in levee affected areas.  The FIS could become a part of the awareness and 
outreach approach or part of the delivery vehicle.
  In Sections 4 through 8, several terms for the 1-percent-annual-chance flood are used interchangeably.  
These include the 100-year flood, the base flood, and the FEMA base flood.  As is the case in Part 4.1., the 
context determines which particular term is used.
  Sacramento County and the City of Sacramento combined to create flood risk maps for the public.  These 
maps included the depth of flooding given various levee failure scenarios, the area of flooding, and the time 
between a levee failure and a flood inundation to one’s property (by zone).  The maps are in color and, with a 
little study, can be extremely informative.  The website is 
http://www.cityofsacramento.org/utilities/flood/Sacramento_Flood_Maps.html.
  The National Association of Homebuilders (NAHB) points out that any move toward mandatory purchase 
of flood insurance behind levees should be supported by analysis indicating that the increased costs to 
homeowners are outweighed by the benefits.  Simply acknowledging that residual risk exists does not 
automatically justify the costs of mandated insurance purchase.  

  The 100-year flood is equivalent to the 1-percent-annual-chance flood, the FEMA base flood, and the base 
flood.
 
 
 
 
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