Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005] 

Appendix N: Data Capture Guidelines 

Summary of Changes 

The following Summary of Changes details revisions of Appendix N subsequent to the initial 
publication of the Draft Appendix N in April 2004. These changes represent new or updated 
guidance for Flood Hazard Mapping Partners. 

Date Affected 
Section(s) 
Summary of Change 
09/2004 All “Preliminary Draft – Not for Distribution” deleted. Dates 
updated to September 2004. 
09/2004 All References to appendices standardized. 
09/2004 All References to North Carolina Department of 
Transportation broadened to Departments of 
Transportation. 
09/2004 All References to WISE and ESRI software have been deleted 
except where WISE software must be specifically 
referenced. 
09/2004 Survey 
Coordinates 
Text revised to specify state plane coordinates using RTK 
and Static, with temporary control pairs. 
09/2004 2.2 Text revised to delete items 5 and 6. 
09/2004 2.3 References to specific surveying equipment deleted. 
09/2004 2.4 Text revised to require underscores rather than spaces in 
names for cross sections. 
09/2004 2.6 and Figure 4 Photographs replaced. Names used to reference 
photographs revised. 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005] 

09/2004 8 Text revised to allow data for approximate survey to be 
entered into a shapefile showing the location and 
attributes. 
09/2004 Figure 50 Revised. 
09/2004 8.4 Fields added for approximate culvert survey. 
09/2004 Figure 52 Revised. 
12/2004 All Headers revised to refer to “Guidelines & 
Specifications…” Version removed from footers. Section-
level and sub-section-level revision dates moved to 
headings. Dates updated to December 2004. Summary of 
Changes added. 
4/2005 All Document date updated to April 2005. 
5/2005 All Document date updated to May 2005. 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Table of Contents 

1 Overview [April 2005]........................................................................................ 1 
2 Basic Survey ............................................................................................................... 3 


2.1 General Survey Requirements [April 2005] ................................................... 3 


2.2 Starting the Survey [April 2005]................................................................... 3 


2.3 Setting Elevation Reference Marks (ERM) [April 2005]................................. 4 


2.4 Naming Structures and Cross Sections [April 2005]........................................ 4 


2.5 Format of Survey Text Files [April 2005] ..................................................... 5 


2.6 Naming Digital Photographs [April 2005] .................................................... 7 
3 Bridge Survey [April 2005] ................................................................................. 8 


3.1 Bridge Sketch [April 2005].......................................................................... 8 


3.2 Bridge Survey Text File [April 2005]............................................................ 9 


3.3 Bridge Photographs [April 2005]................................................................ 10 


3.4 Bridge Survey [April 2005] ....................................................................... 10 


3.5 Close Interstate or Highway Structures [April 2005] .................................... 15 
4 Culvert Survey [April 2005] .............................................................................. 19 


4.1 Culvert Sketch [April 2005]....................................................................... 19 


4.2 Culvert Survey Text File [April 2005] ........................................................ 20 


4.3 Culvert Photographs [April 2005] .............................................................. 21 


4.4 Culvert Survey [April 2005] ...................................................................... 21 
5 Dam Survey [April 2005] ................................................................................. 28 


5.1 Dam Sketch [April 2005]........................................................................... 28 


5.2 Dam Survey Text File [April 2005]............................................................ 30 


5.3 Dam Photographs [April 2005]................................................................... 31 


5.4 Dam Survey [April 2005] .......................................................................... 31 
6 Cross Section Survey ................................................................................................ 38 


6.1 Cross Section Sketch [April 2005] ............................................................. 38 


6.2 Cross Section Survey Text File [April 2005] ............................................... 40 


6.3 Cross Section Photographs [December 2004] ............................................. 40 


6.4 Cross Section Survey [April 2005]............................................................. 40 
7 Overview and Problem Surveys................................................................................ 43 


7.1 Overview Survey [April 2005] ................................................................... 43 


7.2 Channel Shots [April 2005] ....................................................................... 45 


7.3 Skewed Streams [April 2005].................................................................... 45 


7.4 State Plane Coordinates .................................................................................... 47 


7.5 Super-Elevated Curves...................................................................................... 48 


7.6 Relief Structures................................................................................................ 48 
8 Approximate Survey [April 2005]...................................................................... 51 


8.1 Digital Photographs [April 2005] ............................................................... 51 


N-i Table of Contents 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

8.2 DOT Bridge Survey Reports Recon [April 2005] ......................................... 52 


8.3 Approximate Bridge Survey [April 2005] ................................................... 52 


8.4 Approximate Culvert Survey [April 2005].................................................. 53 
9 Historical High Water Marks [April 2005].......................................................... 55 


List of Figures 

Figure 1. Field Survey Flow Chart ................................................................................................ 1 
Figure 2. Formatting Text Files ..................................................................................................... 5 
Figure 3. Sample Survey Shots for a Bridge.................................................................................. 6 
Figure 4. Examples of Digital Photographs................................................................................... 7 
Figure 5. Typical Bridge Sketches................................................................................................. 9 
Figure 6. Examples of Bridge Photographs ................................................................................. 10 
Figure 7. Trapezoidal Opening for Bridge................................................................................... 10 
Figure 8. Bridge Shots ................................................................................................................. 12 
Figure 9. Example of One Rail Height ........................................................................................ 12
Figure 10. Example of Multiple Rail Heights.............................................................................. 12 
Figure 11. Bridge Pier Shots........................................................................................................ 13 
Figure 12. Examples of Low Chords ........................................................................................... 14
Figure 13. Close Bridges.............................................................................................................. 15 
Figure 14. Deck Thickness versus LOW CHORD Shots ............................................................ 16 
Figure 15. Survey Codes for a Bridge ......................................................................................... 17 
Figure 16. Sample Survey Text File using LOW CHORD for a Bridge ..................................... 18 
Figure 17. Typical Culvert Sketches............................................................................................ 20 
Figure 18. Examples of Culvert Photographs.............................................................................. 21 
Figure 19. Profile View of a Culvert ........................................................................................... 23 
Figure 20. Planimetric View of a Culvert.................................................................................... 23
Figure 21. Interpretation of Culvert............................................................................................. 24 
Figure 22. Overlapping Box Culverts.......................................................................................... 24 
Figure 23. Hydraulic Width of Culverts ...................................................................................... 25
Figure 24. Skewed Culverts......................................................................................................... 26 
Figure 25. Sample Survey Text File for a Culvert....................................................................... 27 
Figure 26. Typical Earthen Dam Sketches .................................................................................. 29 
Figure 27. Typical Dam with Riser Sketches .............................................................................. 30 
Figure 28. Examples of Dam Photographs .................................................................................. 31 
Figure 29. Embankment and Top of Dam Shots.......................................................................... 32 
Figure 30. Dam and Water Shots................................................................................................. 33 
Figure 31. Portion of Text for Dam Shots ................................................................................... 33 
Figure 32. Spillway Shots............................................................................................................ 34 
Figure 33. Shots Downstream of Dam......................................................................................... 35 
Figure 34. Sample Survey Text File for a Dam........................................................................... 37 
Figure 35. Example of Cross Section Sketch............................................................................... 39 


N-ii Table of Contents 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 36. Examples of Cross Section Photographs.................................................................... 40 
Figure 37. Sample Survey Text File for a Cross Section............................................................. 42 
Figure 38. Example of Top of Road Shot Coded Incorrectly as GR ........................................... 43 
Figure 39. Profile View of Overview Survey .............................................................................. 44 
Figure 40. Adjusting Problem Bridge Shots................................................................................ 44 
Figure 41. Types of Channel Shots.............................................................................................. 45 
Figure 42. Two Types of Channels.............................................................................................. 45 
Figure 43. Skewed Bridges.......................................................................................................... 46 
Figure 44. Skewed Culvert .......................................................................................................... 46 
Figure 45. Poor and Correct Alignment of Skewed Culvert........................................................ 47 
Figure 46. Codes for State Plane Coordinates ............................................................................. 47 
Figure 47. Relief Structures ......................................................................................................... 49 
Figure 48. Example of Approximate Survey Photograph............................................................ 51 
Figure 49. DOT Bridge Survey Report........................................................................................ 52 
Figure 50. Approximate Bridge Survey....................................................................................... 53 
Figure 51. Hydraulic Width of Bridge......................................................................................... 53 
Figure 52. Approximate Culvert Survey...................................................................................... 54 
Figure 53. Hydraulic Width of Culvert........................................................................................ 54 
Figure 54. Sample Sketch for Historical Flooding Survey.......................................................... 55 


List of Tables 

Table 1. Survey Codes for a Bridge............................................................................................. 17 
Table 2. Survey Codes for a Culvert............................................................................................ 26 
Table 3. Survey Codes for a Dam................................................................................................ 36 
Table 4. Survey Codes for a Cross Section.................................................................................. 42 
Table 5. Optional Survey Codes for Structures and Cross Sections............................................ 49 


N-iii Table of Contents 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

1 Overview [April 2005] 

The open stormwater system is made up of bridges, culverts, dams and stream cross sections. 
Surveying this system consists of initial field reconnaissance and field surveys for hydraulic 
structure geometry and immediate overbank cross section data. The field survey includes 
obtaining channel and floodplain cross sections, identifying or establishing elevation reference 
marks (ERMs) (following guidance in Appendix A: Flood Insurance Study Guidelines and 
Specifications for Study Contractors ), obtaining the physical dimensions of hydraulic and flood 
control structures, and taking photographs at each hydraulic structure and at the location of cross 
sections to determine Manning’s roughness coefficient. A flowchart for the field survey is 
shown. 

Figure 1. Field Survey Flow Chart 

First, a field reconnaissance is conducted. 
The purpose of the field reconnaissance is 
to drive (and walk, if necessary) each 
stream to ensure that all structures are 
accounted for in the modeling. The 
reconnaissance will also identify any 
hydraulic structures on private property that 
will require property owner coordination 
and permission. 

Field Reconnaissance 
Gather Historical 
High Water 
Information 
Field Interviews/ 
Survey Historical 
High Water Marks 
Establish Vertical 
Control (GPS) 
Field Survey, 
Cross Sections 
Field Survey, 
Hydraulic Sections 
Survey Reduction 
Quality Control 
Quality Control 
Survey Technical 
Support Data 
Notebook (TSDN) 
Historical flooding information is 
researched and compiled (published and 
non-published) from available sources 
including FEMA, US Army Corps of 
Engineers, USGS, Departments of 
Transportation, municipalities and other 
agencies and consulting firms. 

In general, the structure surveys obtain the 
structure geometry and the natural ground 
at a hydraulic structure. Each hydraulic 
structure is represented with a combination 
of the natural ground at the upstream face 
of the structure and the roadway profile 
along the centerline or crown of the 
roadway (highest profile. 

The surveyors will set an Elevation Reference Mark (ERM) at each structure. During the survey 
of the structure, the ERM will be shot to give the benchmark an elevation and location (X,Y). An 

N-1 Section 1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

ERM normally will be a chiseled square at the upstream left face of the structure in the head wall 
or wing wall. If a structure does not have a headwall, then a large spike in a telephone pole, top 
of manhole, chiseled square on top of pipe of structure, or on a stable structure will be used. 

For bridge surveys, the roadway profile is defined as the highest-grade line of the road along the 
structure. The survey of the top of road begins, at a minimum, 200 feet down-station from the 
beginning of the structure and ends, at a minimum, 200 feet up-station of the end of the structure. 
The ground points represent the natural ground geometry at the bottom of the fill at the upstream 
face of the structure. 

The survey of a culvert is similar to that of the bridge. The top of road sections and natural 
ground sections are collected in a similar manner as the bridge survey. The upstream and 
downstream inverts of each culvert barrel(s) are also collected, as well as the shape, material, 
dimensions and entrance and exit types (headwalls and wingwalls). 

Three cross sections are surveyed for a dam: an upstream ground (underwater) section of the 
pond or lake, a section across the top of dam, and section downstream of the dam embankment. 
If a spillway is present, elevation points are obtained at the top of dam, top of spillway, and 
bottom of spillway. The upstream and downstream side slope of the dam as well as the top width 
are measured and documented in the survey sketch. If a riser is present, elevations are obtained 
for the top of the riser, the invert of the riser, the inverts of the barrel or outlet works, and any 
obstruction on the riser, such as a metal grate or cover will be noted. The downstream natural 
ground section is obtained off of the fill or bottom of the slope of the dam and surveyed similar 
to upstream section of a bridge or culvert. 

At least four digital photographs are taken at each hydraulic structure. In addition, a detailed 
sketch is made of the structure and vicinity. Sketches for structures include the structure, channel 
banks, edge of water, channel, direction of flow, rails, benchmark location, structure dimensions 
and any historical high water marks and references collected during the survey. 

Hydraulic cross sections are surveyed and included in the hydraulic model. Because of the 
accurate terrain information for the floodplains, only the main channel portions (bank to bank) 
and immediate floodplain areas are field surveyed. This channel geometry information is then 
propagated upstream and downstream in the reaches between bridges. A minimum of two digital 
photographs are taken at each cross section. 

Attempts to obtain historical high water marks are made on every detailed studied stream. In 
some cases, no historical high water information can be obtained for a stream. Information 
acquired from witnesses is: name of the witness, witness’s address, length of residency, type, 
date and frequency of any high water events. Also included is the interviewer’s name, 
photograph, date of interview, and stream location. Permission is obtained from property owners 
prior to any required survey. The high water mark is surveyed and used in later model calibration 
and verification for detailed study streams. 

N-2 Section 1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

2 Basic Survey 

2.1 General Survey Requirements [April 2005] 
Bridges, culverts, dams and cross sections alter and restrict the flow of water and shall be 
recorded in survey notes, sketches and shots. 

Survey Sketches 

The structure survey sketch shall include notes representing the structural geometry and the 
natural ground using standard survey codes. The survey notes shall represent the hydraulic 
opening of each structure as well as surveying the top of road (the highest point) in order to 
determine how high the water must rise to proceed over the road. For a bridge, the survey must 
locate the trapezoidal opening as well as its hydraulic width. In addition, piers restrict the flow of 
water and need to be part of the survey. For a culvert, the hydraulic opening is determined by the 
shape, size, number, and hydraulic widths of the culverts. For a dam, the survey must define the 
height of the dam, the width of the spillway opening, the size and depth of risers, and the 
hydraulic width of the pipe from the riser to the downstream outlet. The survey requirements for 
each structure will be described in detail in this chapter. 

The structure survey sketches will provide a planimetric and profile view of the structure. The 
orientation for sketches should be looking at the upstream face of the structure. A template for 
the structure drawings will be provided. The sketches shall show the structure, piers, 
channelbanks, channel, direction of flow, rails, deck, footings, abutments, culvert inverts, shape 
and size of opening, benchmark location, other dimensions, and other details of the structure. 

Survey Coordinates 

All structure and cross section surveys will be surveyed using state plane coordinates. The two 
acceptible GPS methods are RTK and Static. A mininum of two temporary control points are 
to be set near each structure. Cross section require one control point and using north as a 
backsight bearing. 

Two alignment points need to be shot and coded, ALPT1 and ALPT2, to define the alignment. 
These shots will create a new baseline that is perpendicular to the creek. For more information 
on this, refer to the State Plane Coordinates section in “Overview and Problem Surveys”. 

2.2 Starting the Survey [April 2005] 
Start the survey as follows: 

1. Take the 4 pictures required for the bridge, culvert or dam, the 2 pictures required for 
a levee or channel, or the 2 pictures for a cross section. 
2. Set an elevation reference mark (ERM) in the headwall of the structure. 
N-3 Section 2.1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

3. Provide a sketch of a planimetric and a profile view of the structure and other 
requested structure information on the given template. 
2.3 Setting Elevation Reference Marks (ERM) [April 2005] 
Surveyors must set an Elevation Reference Mark on the upstream left headwall of each structure. 
This could be either a chiseled square or a chiseled X. If there is a chiseled square on one of the 
headwalls, check with any old Flood Insurance Rate Maps to see if this is an old ERM. If so, do 
not create a new ERM. Use the existing one. 

Follow this order of where to set the ERMs. If the first location is unattainable, use the second, 
and so on. 

1. Upstream left headwall; 
2. Upstream right headwall; 
3. Downstream left headwall; 
4. Downstream right headwall; 
5. Spike in a nearby power pole set towards the road and 0.5 feet above the ground; 
6. Top of the rim of a Manhole (not in road); and 
7. Flange bolt of a fire hydrant (not on top). 
All ERMs must have a full description of the location in relation to the structure and road. 

2.4 Naming Structures and Cross Sections [April 2005] 
All structures and cross sections shall have a unique ID. A structure name should have the stream 
name or the abbreviated name followed by the number of the structure on that stream. All 
numbers start from the downstream limit and increase upstream. 

There are many ways to create a naming scheme for a project. One common method is to 
abbreviate the stream name. For example, SC3 is the third structure from the downstream limit 
on Swift Creek. Swift Creek would be SC. If there is another stream in the project with a SC 
(Swan Creek), then change SwiftCreek to STC and SwanCreek to SNC. 

Another example of naming files is to just use the first name of the stream. For example, Swift 
Creek would be Swift and Swan Creek would be Swan. This could be a problem if there are 
streams with long names or if the project has many names with Tributary in them. 

The file name will use underscores to indicate spaces in the name of the cross section. Each 
survey file must have a unique file name. For example, XS_1.txt. 

Before surveying, review all the stream names to determine the best way to name the files and 
streams. Create a list of all the streams that are to be surveyed and find all the crossing and street 

N-4 Section 2.3 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

names of that stream. This way a structure ID will already be assigned where the stream crosses 
the road. 

Once in the field, there may be a time when a new road is built and is not on the current map or 
the bridge is in a park or private property. These will need to be surveyed as all structures need to 
be surveyed that cross the stream within the study limits. If all the IDs are assigned, use the letter 
A at the end of the ID. For example, SC3 would represent the third structure and SC3A would 
represent the fourth structure upstream. 

2.5 Format of Survey Text Files [April 2005] 
For quality control, the surveyors are usually directed to take the first two shots in the field as the 
occupying point (OCC) and the back sight (BS) and to describe them as control points. These 
two shots should remain in the survey, but two additional shots to describe the structure need to 
be added above these shots. To save the OCC and BS points, copy shots 1 and 2, the OCC and 
the BS, and paste them at the top of the survey. Now there should be two OCC and two BS 
points. The first two descriptions can be changed to describe the structure, but the OCC and BS 
descriptions will remain in the survey. 

Figure 2. Formatting Text Files 

data collector 

1,13878618.350,3023941.825,121.122,GPS_H_LAN_11B2,13878984.000,3023921.366,118.635,GPS_H_LAN_11A3,13878308.673,3023976.571,118.083,ALPT24,13878304.382,3023963.576,118.419,OPEN5,13878351.112,3023944.586,118.516,GR6,13879068.480,3023995.192,119.164,TR 

First 2 shots copied and replaced with appropriateDescriptions and header included. 
U00-10 
1,13878618.350,3023941.825,121.122,BR U00-10 92 1.92,13878984.000,3023921.366,118.635,QUEENSTON DRIVE1,13878618.350,3023941.825,121.122,GPS_H_LAN_11B2,13878984.000,3023921.366,118.635,GPS_H_LAN_11A3,13878308.673,3023976.571,118.083,ALPT24,13878304.382,3023963.576,118.419,OPEN5,13878351.112,3023944.586,118.516,GR

6,13879068.480,3023995.192,119.164,TR 

The first two shots are changed later in the office. The first two descriptions are changed to 
define the structure and some of its measurements. 

N-5 Section 2.5 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

For a bridge, the code should read BR SC3 46 2.2. This code means BR for bridge, SC3 is the 
ERM ID, 46 is the width of bridge, and 2.2 is the deck thickness. 

A culvert’s first code is as follows: CUL SC2 78. The CUL represents culvert, SC2 is the ERM 
ID, and 78 is the hydraulic width of the culvert. 

A dam’s first code is as follows: DAM SC4 22 1.8. The DAM represents a dam, SC4 is the 
ERM ID, 22 is the width of the top of dam, and 1.8 is the embankment side slope. 

The first shot for a cross section only needs XS, for cross section, and the ERM ID. The second 
shot’s code is the street name in which the stream crosses. 

Survey text files should be comma-delimited (text only). The first field shall be the shot number 
follow by the northing field, easting field, elevation field, and description field. Finally, a header 
needs to be inserted in the first line of the text file. The header will be the same as the structure 
name. All structure names must be unique. There cannot be a duplicate name in the project. 
Below is an example of a typical survey file. 

Figure 3. Sample Survey Shots for a Bridge 

WK_BGBR11 
1,764213.544,2111149.97,286.890,CUL WK_BGBR11 982,764213.544,2111149.97,286.890,MILLBROOK ROAD0624,764213.544,2111149.97,286.890,W BIB 9A0625,764248.160,2110789.62,319.450,W BIB 9B1035,764248.463,2111423.05,275.042,ERM1009,765047.017,2111729.83,283.641,TR1010,765067.885,2111740.81,287.721,GR1014,765097.525,2111650.99,283.330,CB1015,765096.980,2111645.21,277.763,TE1016,765093.222,2111640.97,277.676,H2O1017,765093.734,2111639.07,277.697,UIB1 7 101018,765094.884,2111636.03,277.653,H2O1019,765096.338,2111632.30,277.678,H2O1020,765097.258,2111629.27,277.663,UIB2 7 101021,765099.064,2111624.86,277.725,H2O1022,765099.514,2111623.31,277.751,TE1025,765108.556,2111614.26,282.566,CB1030,765039.783,2111581.57,286.862,ALPT21031,765010.312,2111670.01,283.829,ALPT11032,764995.459,2111643.25,271.066,DS IN1033,764995.300,2111643.31,274.050,DIB1 7 101034,764999.754,2111632.38,274.163,DIB2 7 10 

It is assumed that a survey code is upstream (US) unless it is identified 
as downstream.To identify a downstream shot, the surveyor must add 
DS after the survey code, such as GR DS or CB DS. 

N-6 Section 2.5 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

2.6 Naming Digital Photographs [April 2005] 
Every structure and cross section will have a unique identification name. The photos taken at the 
structure or cross section will share that same identification name. 

Four digital photos will be taken for each structure and two digital photos taken for each cross 
section. Each digital photo will be named using the identification name followed by an 
underscore and the picture number. For example, if the structure identification name is E_BEB3, 
picture 1 (US face) would be called E_BEB3_USF.PNG, picture 2 (US channel) would be 
called E_BEB3_USC.PNG. 

.. E-BEB3_USF.PNG – Upstream face; 
.. E-BEB3_USC.PNG – Upstream channel; 
.. E-BEB3_DSC.PNG – Downstream channel; and 
.. E-BEB3_DSF.PNG – Downstream face. 
Figure 4. Examples of Digital Photographs 


N-7 Section 2.6 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

3 Bridge Survey [April 2005] 


The Merriam-Webster definition of a bridge is “a 
structure carrying a pathway or roadway over a 
depression or obstacle.” Unlike a culvert, a bridge 
has an earthed floor underneath rather than a 
cement bottom.1 

3.1 Bridge Sketch [April 2005] 
Each sketch for a bridge shall include the following: (use the template if provided): 

.. Project Name – Name of project or the area being studied; 
.. Stream Name – Name of the studied stream; 
.. Location – Road name that crosses the stream; 
.. Date of survey; 
.. FEMA Contract number; 
.. File name – Survey file name in the data collector; 
.. Surveyors – Names of those surveying, listed as last name, comma, first initial; 
.. ERM ID – Specific location and type of benchmark (i.e. USGS benchmark disk on the 
upstream left headwall.); 
.. Elevation – Elevation of the ERM in the correct datum; 
.. Bridge hydraulic width – The distance that the stream flows through the structure. For 
example, a bridge whose roadway is 20' wide, but whose rails, piers, or sidewalk extends 
out one foot on each side of the structure would be 22' wide. 
.. Rail height – Distance from the road to the top of the rail; 
.. Deck thickness – Distance from top of road to low chord (top of opening of bridge); 
.. Pier dimensions; 
.. North Arrow; 
.. Direction of stream flow; and 
.. Photo IDs and Location – location and direction of where the photo was taken. Place the 
circled photograph number where the picture was taken and an arrow in the direction the 
photograph was taken. 
1 Merriam-Webster Dictionary, 10 ed., s.v. “bridge.” 

N-8 Section 3.1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Each sketch shall include both planimetric and profile view. The profile view should be oriented 
looking downstream at the upstream face of the structure. The sketches shall show the structure, 
piers, channel banks, channel, direction of flow, rails, deck, footings, abutments, ERM location, 
other dimensions, etc. A typical sketch is shown. 

Figure 5. Typical Bridge Sketches 


3.2 Bridge Survey Text File [April 2005] 
See the end of this section for an example of a Survey Text File for a Bridge. A header or a 
structure name is needed above the first shot of that text file. Each text file should have a unique 
header. 

After the header, two shots or entries that provide the program with a useful description of the 
structure must follow the header. Shot number one provides the type of structure, the ERM for 
the structure, bridge width, and the deck thickness. 

For example, BR SF4 24 3.0 identifies the structure as a bridge (BR), the ERM ID is SF4, the 
bridge width is 24 feet, and the deck thickness is 3.0 feet. The second shot provides the street 
name of the bridge. The street name for this bridge is Stanley-Spencer Mountain Road. 

N-9 Section 3.2 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

3.3 Bridge Photographs [April 2005] 
A minimum of four digital photographs will be submitted for each bridge. The required aspects 
or view of the photographs include: 

.. SOMEWHERE_RD_USF. Standing upstream of structure, looking downstream at the 
structure; 
.. SOMEWHERE_RD_USC. Standing on or below the structure, looking upstream at the 
channel; 
.. SOMEWHERE_RD_DSC. Standing on or below the structure, looking downstream at 
the channel; and 
.. SOMEWHERE_RD_DSF. Standing downstream of structure, looking upstream at the 
structure. 
Figure 6. Examples of Bridge Photographs 


3.4 Bridge Survey [April 2005] 
It is the surveyors’ responsibility to identify what will interfere or obstruct the flow of water. The 
survey should represent the hydraulic opening of all structures as well as surveying the top of 
road (the highest point to determine how high the water must rise to proceed over the road). With 
a bridge, the survey must locate the trapezoidal opening as well as its hydraulic width. Piers also 
restrict the flow of water and need to be part of the survey. 

Figure 7. Trapezoidal Opening for Bridge 


N-10 Section 3.3 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

There are a variety of shots and codes that are needed to represent a bridge. A bridge requires 
structure data and two cross sections to be surveyed, a top of road section (TR) and a ground 
section (GR). The following shots are descriptions used in the survey: top of road data (TR, 
BEGIN, END, RAIL), the structure data (P1 1.0, TOE, DS IN), and the ground section (GR, 
CB, TE, H2O). The table at the end of this section lists more in detail the valid codes required 
for a bridge survey. 

The ground (GR) section shall represent the natural ground at the bottom of the fill. The survey 
of the ground shall extend 200 feet from each channel bank running perpendicular to the creek. 
The ground section should represent where the water will go once the water goes outside the 
channel. The stream channel is defined as the water being contained in the channel at normal 
levels. The stream channel should be surveyed at the upstream face of the bridge. 

A common method of surveying the stream channel is to take the channel shots from the top of 
the upstream side of the bridge. The survey codes for the stream channel are CB (channelbank), 
TE (top and edge), and H2O (water). All bridges must have two CBs, two TEs, and adequate 
number of H2O shots. Channelbank (CB) is defined as the top of the stream channel. Top and 
edge (TE) of water is defined as the top of the water in the streambed and where the water meets 
the land or the side of the channel. The number of water shots taken depends on the size of the 
channel. Water shots should be taken where there is a break in elevation in the channel. If the 
water is not clear, then probe the water to find any change in depth. There should be a minimum 
of three H2O shots. Two of those shots are at the bottom of the slope of the creek bed. If there is 
only one H2O shot in the middle of the creek, the representation of the channel would look like a 
“V”. 

Top of Road 

The top of road (TR) points defines the highest-grade line of the road along the structure. The 
survey of the top of road shall begin, at a minimum, 200 feet down-station from the beginning of 
the structure and end, at a minimum, 200 feet up-station of the end of the structure. The 
beginning (BEGIN) and end (END) of bridge is defined as the top of road where the abutment 
begins. The BEGIN is the start of the left abutment and the END is the start of the right 
abutment. The top of the abutment is calculated by taking the top of road elevation (coded 
BEGIN and END) and subtracting the deck thickness. The deck thickness is coded within the 
first shot of the surveyed text file. (See the Code List at the end of this section). If the top of road 
is earthen and not asphalt or concrete, the TR is still used as a code even if it appears to be 
ground. A footbridge is an example of having an earthen top of road. 

N-11 Section 3.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 8. Bridge Shots 


Rail 

If there is a rail on the bridge, use a RAIL shot. The RAIL shot will be taken on top of the rail 
where the rail begins and ends. If the rail appears to change heights, survey a RAIL shot where 
there is a significant change in elevation. See example below (Figure 18). There should be a 
minimum of two rail shots for each set of rail heights that will be averaged for the rail height. 

Figure 9. Example of One Rail Height 


Figure 10. Example of Multiple Rail Heights 


Other Codes 

Other codes need to be in the survey (Piers, TOE, DS IN, ERM, and alignment points (ALPT)), 
but not all bridges will have Piers or TOEs. 

TOEs are only needed if the abutment is on an angle (not straight down). In some of the older 
bridges, the abutments are at a 90-degree angle (straight down). In these cases, a TOE code is 
not needed. The BEGIN and END codes will still be taken on the top of the road at the abutment 
stationing. The TOEs will be generated automatically by drawing a line from the top of the 
abutments, created by the BEGIN and END, to the natural ground created by the GR section. 

N-12 Section 3.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Footbridges are built directly over a channel and will not have an abutment (TOE shot) as shown 
in Figure 18. 

Piers 

The pier shots (P2 1.0) have to be taken on the upstream face of the bridge and at its base. Piers 
will be coded as one continuous solid pier. Piers are also coded within the field data. Do not 
shoot another GR of H2O at the piers. If a pier is in a scour hole, survey the pier base as if it 
were filled in. In order to compensate, either raise the rod directly in front of the pier over the 
scour hole at the normal ground or extend the rod out in front of the pier until the normal ground 
is represented. Do not survey anything in a scour hole. If there is a footing or a cap, write the 
measurements (height and width) in the additional comments section of the drawing template. 

The pier description must be followed by a pier number and its thickness (P1 1.5). The Piers are 
numbered from left to right. The piers are coded as part of the ground section. If there is a pier in 
the water, that pier will also be a water (H2O) shot. 

Below is an example of where to take the shot with a pier in a scour hole, and also to survey pier 
2 as a water shot. Other shots were omitted to avoid clutter. 

Figure 11. Bridge Pier Shots 


In the example above, the TOE shots were taken but not needed. This is a surveyor’s option. 
Survey the TOE shots on a vertical abutment if there was a change in elevation. 

Low Chord (LC) 

The surveyor must supply either the deck thickness or one or more low chords. The deck 
thickness is defined as the distance between the top of road elevation and the bottom of the 
bridge deck or low chord. 

N-13 Section 3.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 12. Examples of Low Chords 

If the surveyor provides low chords without a 
deck thickness, an average deck thickness is 
calculated based on the low chords. If only one 
low chord is provided without a deck thickness, 
the deck thickness is calculated and stored, 
based on the low chord, as well as the actual 
elevation. If both a deck thickness and low 
chords are provided, both are stored but the LC 
code is used to calculate the deck thickness. LC 
codes are used if the actual deck thickness 
measurement is hard to obtain or if there is a 
super elevated turn. Shoot two LCs if there are 
multiple low chords. 


Upstream and Downstream Faces of Structure 

The USSTRUCT and DSSTRUCT codes are required as they measure the hydraulic width of the 
structure. The shots are to be taken on top of the bridge at the upstream (USSTRUCT) and 
downstream (DSSTRUCT) face of the structure over the stream. Using these codes will overwrite 
the existing hydraulic width value found in the first shot. 

Elevation Reference Mark and Downstream Invert 

All bridges and culverts need an ERM and a DS IN. The ERM, or Elevation Reference Mark, 
must be set and surveyed at each structure. The ERM is a temporary benchmark to be referenced 
later. The DS IN, or DownStream INvert, is the deepest water shot taken on the downstream 
side on the bridge. Avoid taking a DS IN in a scour hole. If the downstream channel has a rocky 
bottom due to the construction of the bridge, probe through the rocks to find the stream bottom, 
otherwise move a little downstream where the streambed is attainable. 

N-14 Section 3.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

3.5 Close Interstate or Highway Structures [April 2005] 
For bridges only, there are cases when two 
bridges are close enough to be modeled as 
one structure. Bridges are only to be 
modeled as one structure when two bridges 
are less than 50 feet from one another and 
they share the same shape. For example, the 
two bridges have the same deck thickness, 
rails, abutments, and number and shape of 
piers. These close structures are commonly 
found on major highways and interstates and 
were built using the same plans. 

The ground section will be surveyed on the 
upstream side of the upstream structure and the downstream invert will be taken on the 
downstream side of the downstream structure. The top of road section will be taken at the highest 
elevated road. The low cord or the deck thickness will be measured between the highest elevated 
road and the lowest deck. 

For example, if the highest elevated road is at an elevation of 100 feet and the lowest elevated 
road is at 96 feet with a deck of 2 feet. The deck thickness will be calculated to the difference 
between the two road elevations (4 feet) and adding the deck (2 feet), which makes the deck 6 
feet. An LC shot can be shot in lieu of measuring a deck thickness. The hydraulic width of the 
bridge will be the sum of the two widths of each bridge and the distance separating the two 
bridges. If the two bridges were 42 feet wide with a distance of 26 feet in between them, the 
width of the bridge would be 110 feet. 

Figure 13. Close Bridges 


N-15 Section 3.5 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 14. Deck Thickness versus LOW CHORD Shots 

Either Deck Thickness or LOW CHORD shots 
may be used to determine deck thickness. 

1,13900360.570,3139785.132,58.530,BR P00-30 38.0 3.0 

OR 

7,13900357.033,3139829.593,60.541,BEGIN 
10,13900357.033,3139829.593,57.341,LC 
8,13900195.454,3139835.912,60.307,END 
11,13900195.454,3139835.912,57.507,LC 

Thickness for shot 10 is 3.2 feet. 
Thickness for shot 11 is 2.8 feet. 
Deck thickness is calculated at 3.0 feet.


N-16 Section 3.5 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Table 1. Survey Codes for a Bridge 

Valid Codes Example Notes for use 
HEADER 
Structure Type ERM 
Hydraulic width Deck 
BR SF4 24 3.0 
Shot 1 only. Bridge with ERM ID, Hydraulic width 
and Deck Thickness. If Deck Thickness is 
supplied, it is not necessary to use LOW CHORD 
Road Name Mountain Road, Interstate 85 Shot 2 only. 
FIELD SHOTS (Bridge) 
ERM ERM SF4, ERM N_TAR-4 Elevation reference mark 
TR TR Top of Crown Data 
BEGIN BEGIN Top of Crown at Begin Abutment 
END END Top of Crown at End Abutment 
RAIL RAIL Top of Rail. Must be inside TR. 
GR GR Ground Field Data 
CB CB Channelbank 
P? Width P1 3.0, P4 2.3 Pier #1 and Width 
TOE TOE Toe of Fill Station 
TOE TE TOE TE Toe of Fill Station and Edge H2O 
TE TE Edge H2O 
H2O H2O Underwater Field Data Shot 
HIS HIS Historical Shot 
DS IN DS IN Downstream Invert for Bridge 
OPEN OPEN Open Area Field Shot 
BRUSH BRUSH High Brush Field Shot 
WOOD WOOD Wooded Canopy Field Shot 
ALPT ALPT1, ALPT2 Alignment points (left, right) 
LC or LOW CHORD LC 
Bottom of suspension structure. Must be inside 
of Begin and End. If LC is used, it is not 
necessary to supply Deck Thickness. 

Figure 15. Survey Codes for a Bridge 

OPEN OPEN 
N-17 Section 3.5 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 16. Sample Survey Text File using LOW CHORD for a Bridge 

U20-2 
1,13878649.380,3019506.624,120.841,BR U20-2 76.0 
2,13879384.780,3019487.254,122.978,BARKER CYPRESS 
1,13878649.380,3019506.624,120.841,H_DIN_1 
2,13879384.780,3019487.254,122.978,H_LAN_12 
3,13878581.860,3019520.325,104.740,H2O 
4,13878582.852,3019519.517,104.808,H2O 
5,13878585.552,3019518.683,105.680,TE 
6,13878605.509,3019519.738,110.907,P1 1.4 
7,13878638.154,3019516.560,119.458,GR 
8,13878650.431,3019515.926,121.042,GR 
9,13878660.838,3019517.306,121.266,TOE 
10,13878661.048,3019517.407,122.532,LC 
11,13878657.988,3019498.682,122.015,CB 
12,13878742.104,3019509.338,122.306,GR 
13,13878801.661,3019506.965,121.947,GR 
14,13878859.131,3019506.000,122.218,GR 
15,13878896.482,3019504.989,122.124,GR 
16,13878896.515,3019504.989,122.124,OPEN 
17,13878899.260,3019527.576,123.943,ALPT1 
18,13878899.977,3019539.121,124.101,TR 
19,13878842.998,3019541.268,124.470,TR 
20,13878786.292,3019543.254,124.859,TR 
21,13878731.543,3019545.490,125.232,TR 
23,13878696.666,3019548.514,129.085,RAIL 
24,13878669.845,3019535.840,125.154,BEGIN 
25,13878619.904,3019549.086,125.230,TR 
27,13878502.279,3019541.545,125.157,END 
28,13878504.890,3019552.787,125.252,TR 
30,13878463.567,3019559.801,126.589,RAIL 
31,13878449.010,3019554.153,125.832,TR 
32,13878384.540,3019556.611,126.009,TR 
33,13878328.447,3019559.033,126.086,TR 
34,13878273.629,3019560.861,126.214,TR 
35,13878273.511,3019549.542,126.083,ALPT2 
36,13878270.766,3019519.814,124.902,OPEN 
37,13878270.719,3019519.815,124.901,GR 
38,13878337.985,3019517.340,123.184,GR 
39,13878400.862,3019511.553,122.275,GR 
40,13878463.913,3019509.565,122.225,GR 
41,13878496.103,3019513.638,122.083,CB 
42,13878503.521,3019522.387,122.134,TOE 
43,13878503.468,3019522.142,122.653,LC 
44,13878512.950,3019521.211,119.852,GR 
45,13878548.091,3019521.401,110.564,P2 1.4 
46,13878565.061,3019518.663,105.694,TE 
47,13878567.956,3019518.266,104.878,H2O 
48,13878577.880,3019520.488,125.466,ERM UC 
49,13878663.015,3019517.676,125.513,USSTRUCT 
50,13878676.048,3019592.510,125.520,DSSTRUCT 
51,13878615.852,3019595.333,105.260,DS IN 
52,13879384.780,3019487.265,122.958,H_LAN_12 

N-18 Section 3.5 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

4 Culvert Survey [April 2005] 

The definition of a culvert is a prefabricated 
structure carrying a pathway or roadway over a 
depression or obstacle. Unlike a bridge, a culvert 
has a concrete or metal bottom. 


4.1 Culvert Sketch [April 2005] 
Each sketch for a culvert shall include the following (use the template if provided): 

.. Project Name - Name of project or the area being studied; 
.. Stream Name – Name of the studied stream; 
.. Location – Road name that crosses the stream; 
.. Date of survey; 
.. FEMA Contract number; 
.. File name – Survey file name in the data collector; 
.. Surveyors – Names of those surveying, listed as last name, comma, first initial; 
.. ERM ID - Specific location and type of benchmark (i.e. USGS benchmark disk on the 
downstream left headwall, chiseled square on the upstream left headwall.); 
.. Elevation – Elevation of the ERM in the correct datum; 
.. Culvert length - The distance that the stream flows through the structure. If the 
culvert has a bend, this needs to be factored into the culvert hydraulic width. 
.. Type - The type of culvert (i.e. concrete box, circular concrete pipe, elliptical metal 
pipe, etc); 
.. Number – Number of openings; 
.. Rail height - Distance from top of road to top of rail. (If any); 
.. North Arrow; 
.. Direction of stream flow; and 
.. Photo IDs and Location – location and direction of where the photograph was taken. 
Place the circled photograph number where the picture was taken and an arrow in the 
direction the photograph was taken. 
N-19 Section 4.1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005] 
N-20 Section 4.2 
Each sketch shall include both planimetric and profile view. The profile view should be oriented 
looking at the upstream face of structure. The sketches shall show the shape of the structure, 
culvert inverts, number and size of opening, channelbanks, channel, direction of flow, rails, 
ERM location, dimensions, etc. A typical sketch for a culvert is shown. 
4.2 Culvert Survey Text File [April 2005] 
The text file must begin with two shots or entries that provide the program with a useful 
description of the structure. Shot number one provides the type of structure, the abbreviated 
name, and the culvert hydraulic width. For example, CUL AC2 99 identifies the structure as a 
culvert (CUL), the identification of the culvert is AC2, and the culvert hydraulic width is 99 feet. 
The second shot provides the street name of the culvert. The end of this section shows an 
example of a survey text file for a culvert. A header or a structure ID is needed above the first 
shot of that text file. Each text file should have a unique header. 
Figure 17. Typical Culvert Sketches 

Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

4.3 Culvert Photographs [April 2005] 
A minimum of four digital photographs will be submitted for each culvert. The required aspects 
or view of the photographs include: 

.. SOMEWHERE_RD_USF. Standing upstream of structure, looking downstream at the 
structure; 
. SOMEWHERE_RD_USC. Standing on the structure, looking upstream at the channel; 
.. SOMEWHERE_RD_DSC. Standing on the structure, looking downstream at the 
channel; and
. SOMEWHERE_RD_DSF. Standing downstream of structure, looking upstream at the 
structure. 
Figure 18. Examples of Culvert Photographs 


4.4 Culvert Survey [April 2005] 
It’s the surveyor’s job to see what will interfere with or obstruct the flow of water. The survey 
should represent the hydraulic opening of all structures as well as surveying the top of road (the 
highest point to determine how high the water must rise to proceed over the road.) With a 
culvert, the survey must locate the opening of the culvert(s) as well as its hydraulic width. The 
culvert headwalls and columns do not need to be surveyed. The three types of culvert are 
Circular Pipe (P), Elliptical (E), and Box (B). 

Top of Road 

The following shots are descriptions used in the survey: top of road data (TR, TR RAIL 2.0), 
the structure data (UIB1 7.0 7.0, DIB2 7.0 7.0, DS IN), and the ground section (GR, CB, TE, 
H2O). See the code list at the end of this culvert section for the first two shots description and 
the following field shots. 

The top of road (TR) points define the highest-grade line of the road along the structure. The 
survey of the top of road shall begin, at a minimum, 200 feet down-station from the beginning of 
the structure and end, at a minimum, 200 feet up-station of the end of the structure. 

N-21 Section 4.3 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

If there is a rail near the culvert, use a RAIL shot. The RAIL shot will be taken on top of the rail 
where the rail begins and ends. If the rail appears to change heights, survey a RAIL shot where 
there is a significant change in elevation. There should be a minimum of two rail shots for each 
set of rail heights. 

Ground Section 

The ground (GR) points shall represent the natural ground at the bottom of the fill. The survey of 
the ground shall extend 200 feet from each channel bank running perpendicular to the creek. The 
ground section should represent where the water will go once the water goes outside the channel. 
The stream channel is defined as the stream water being contained in the channel at normal 
levels. The stream channel should be surveyed at the upstream face of the culvert. 

The survey codes for the stream channel are CB (channelbank), TE (top and edge), and H2O 
(water). All culverts must have two CBs, two TEs, and adequate number of H2O shots. 
Channelbank (CB) is defined as the top of the stream channel. Top and edge (TE) of water is 
defined as the top of the water in the streambed and where the water meets the land or the side of 
the channel. Water (H2O) is defined as the shots in the water at the bottom of the streambed. 

The number of water shots taken depends on the size of the channel. Water shots should be taken 
where there is a break in elevation in the channel. If the water is not clear, then probe the water 
to find any change in depth. There should be a minimum of three H2O shots. Two of those shots 
are at the bottom of the slope of the creek bed. If there is only one H2O shot in the middle of the 
creek, the representation of the channel would look like a “V”. 

Culvert Shots 

All culvert shots must be in the center of openings (inverts). The following descriptions are 
examples of three 10’ high and 8’ wide box culverts with a 2’ thickness. The sketches that follow 
the description explain the three different ways to obtain the shots for these boxes. Use only one 
method for each box. 

.. Recommended Method 
The first box is given a code of UIB1 10 8. This means Upstream Invert of Box 1 with a 

height of 10 and a width of 8. 

OR 

.. Method Two 
The second shot is taken at the top of the opening of box 2 given a code of UTB2 10.0 

8.0 0.0. This means Upstream Top of Box 2 with a height of 10, a width of 8, and a 
thickness of 0. 
OR 
N-22 Section 4.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

.. Method Three 
The third shot is taken at the top of the structure of box 3 given a code of UTB3 10.0 8.0 

2.0. This means Upstream Top of Box 3 with a height of 10, a width of 8, and a thickness 
of 2. 
A pipe culvert is done the same way except “P” (pipe) is used rather than “B” (box). In the 
example below, UIP4 3.5 is used. This means Upstream Invert of Pipe 4 (fourth culvert) with a 

3.5 diameter opening. 
For all culverts, you must survey the downstream inverts of each culvert opening as well as 1 
downstream channel invert shot. 

Figure 19. Profile View of a Culvert 


Figure 20. Planimetric View of a Culvert 


Any of the above methods of coding a culvert can be used. There can be any number of reasons 
to use these assortments of shots. There will be times when the shots need to be at the top of the 
culvert. Some of these examples are rod height restrictions, undercut pipes, and sediment in the 
culvert. Only one of these types of shots needs to be taken for each culvert. The recommended 
method is surveying the invert of the culvert. 

N-23 Section 4.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

These shots are interpreted by taking the location and elevation of that surveyed shot and 
drawing a box, circle, or an elliptical pipe. At a surveyed point coded UIB1 10 8, a line 4 feet 
from either side of that point (8’ wide) is drawn, the line is extended up to 10 feet in height, and 
then the rectangle is closed. If the shot was UTB2 6 4 1.5, a value of 1.5 is subtracted to find the 
top of the box opening, then draw a line 2 feet from either side (4’ wide), subtract the height (6’) 
to find the invert, and then close the rectangle. If the shot was surveyed at the top of the opening 
of the culvert, the thickness would be zero. 

Figure 21. Interpretation of Culvert 


If the surveyed inverts are not in the center of the culvert, there will be an overlap with the 
boxes. See the following example. There are two boxes at 10 feet wide with a 1-foot divider. If 
the inverts are taken 1 foot towards that divider for each culvert, the divider will not be drawn 
and the culverts will merge into one. The divider will be calculated by culvert shots. The exact 
size of the divider is not important. If the divider is 1 foot and the survey only measures the 
distance between the culverts at 0.7 that is fine. The main concern is the size of the boxes and the 
inverts of the culverts in the center of the boxes. 

Figure 22. Overlapping Box Culverts 


Hydraulic Width 

There are a few ways to measure the hydraulic width of the culvert. The first method is to find 
the distance between the upstream and downstream inverts of each culvert. Many data collectors 

N-24 Section 4.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

can determine the distance automatically between two points. The distance between UIB1 and 
DIB1 should be measured to get the hydraulic width of box 1. 

Another method is to use a tape measure. This measurement must be made inside the culvert. 
Measuring the culvert from the top of the road may create a bend in the tape. When there is a 
bend in the culvert, survey on top of the road where that bend is located underground. Use that 
shot to help determine the true hydraulic width with the bend. 

Figure 23. Hydraulic Width of Culverts 
Upstream and Downstream Faces of Structures 

The USSTRUCT / DSSTRUCT codes are required as they measure the hydraulic width of the 
structure. The shots are to be taken on top of the middle culvert at the upstream (USSTRUCT) 
and downstream (DSSTRUCT) face of the structure. Using these codes will over-write the 
existing hydraulic width value found in the first shot. Do not use these shots if there is a bend in 
the culvert. 

Flared or Skewed Culverts 


Flared culverts or cut to fill culverts are usually elliptical and 
will be coded with an E for the third letter of the code. The 
measurements, culvert width, and the invert shots are to be 
taken where the entire culvert is enclosed, as shown in the 
photograph. 

There is a common problem with measuring skewed box culverts. Measuring the face will not 
give the correct measurement of the box. The correct way to measure the width of this type is to 
measure the inside of the box at a 90-degree angle. Below is an example of a skewed culvert. 
The height shouldn’t need any correction. 

N-25 Section 4.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 24. Skewed Culverts 


Table 2. Survey Codes for a Culvert 

Valid Codes Example Notes for use 
HEADER 
Structure Type BM Hydraulic width 
CUL AC2 99 
Shot 1 only. Culvert with 
Benchmark and Hydraulic width of 
the Culvert. 
Road Name Garrison Boulevard Shot 2 only. 
FIELD SHOTS (Culvert) 
ERM ERM AC2, ERM N_TAR-4 Elevation reference mark 
TR TR Top of Crown Data 
RAIL RAIL Top of Rail 
GR GR Ground Field Data 
TE TE Edge H2O 
H2O H2O Underwater Field Data Shot 
CB CB Channelbank 
DS IN DS IN Downstream Invert for Culvert 
OPEN OPEN Open Area Field Shot 
BRUSH BRUSH High Brush Field Shot 
WOOD WOOD Wooded Canopy Field Shot 
ALPT ALPT1, ALPT2 Alignment points (left, right) 
UIB# Height Width UIB2 10.1 10.8 Upstream Invert Box 2 
DTE# Height Width Thick DTE3 5.6 7.9 0.5 DS Top Ellipse 3 
DTP# DIA Thick DTP1 7.0 0.3 DS Top Pipe 1 
DS = Downstream 
US = Upstream 
I = Culvert Invert @ Centerline 
T = Top of Culvert @ 
Centerline 
B = Box, P = Pipe 
E = Elliptical Culvert 

N-26 Section 4.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 25. Sample Survey Text File for a Culvert 

U20-10 
1,13884469.810,3007486.297,138.149,CUL U20-10 103 
2,13884259.280,3007429.304,137.770,FRY ROAD 
1,13884469.810,3007486.297,138.149,H_DIN_5A 
2,13884259.280,3007429.304,137.770,H_DIN_5B 
3,13884460.767,3007487.914,138.641,ERM UL 
5,13884463.554,3007489.669,140.164,RAIL 
9,13884334.867,3007352.793,140.282,RAIL 
10,13884369.190,3007388.005,136.927,CB 
11,13884382.836,3007402.634,130.055,GR 
12,13884389.167,3007409.621,126.388,TE 
13,13884392.584,3007413.345,125.198,H2O 
14,13884401.096,3007421.951,125.312,H2O 
15,13884409.258,3007430.658,125.251,H2O 
16,13884412.533,3007433.970,126.452,TE 
17,13884419.368,3007441.749,130.167,GR 
19,13884405.138,3007426.358,125.136,UIB1 10 12 
20,13884396.147,3007416.877,124.957,UIB2 10 12 
21,13884320.947,3007487.795,124.456,DIB2 10 12 
22,13884330.293,3007496.827,124.476,DIB1 10 12 
23,13884323.690,3007491.363,124.790,DS IN 
24,13884324.557,3007491.103,140.702,DSSTRUCT 
25,13884400.790,3007422.646,140.634,USSTRUCT 
26,13884371.046,3007443.994,139.591,TR 
27,13884411.521,3007486.597,138.645,TR 
28,13884454.685,3007532.734,137.048,TR 
29,13884493.927,3007575.721,136.904,TR 
32,13884585.876,3007672.269,137.000,ALPT1 
33,13884622.115,3007634.222,138.055,BRUSH 
34,13884622.143,3007634.198,138.056,GR 
35,13884575.007,3007595.595,137.593,GR 
36,13884534.003,3007552.524,137.808,GR 
37,13884490.380,3007505.049,137.749,GR 
38,13884453.493,3007468.610,137.905,CB 
39,13884357.223,3007373.035,136.691,GR 
40,13884313.299,3007325.663,136.863,GR 
43,13884233.382,3007238.533,137.281,BRUSH 
44,13884202.589,3007265.291,136.857,TR 
45,13884241.347,3007306.893,137.137,TR 
46,13884283.134,3007351.250,137.190,TR 
48,13884320.543,3007390.211,137.992,ALPT2 
50,13884259.280,3007429.306,137.693,H_DIN_5 

Except for the first two shots or entries, these shots can be in random order and do 
not need to follow this pattern as long as valid codes are used. A header or a 
structure ID is needed above the first shot. 

N-27 Section 4.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

5 Dam Survey [April 2005] 

The Encyclopædia Britannica definition of a dam is “structure built across a stream, river, or 
estuary to retain water. Its purposes are to meet demands for water for human consumption, 
irrigation, or industry; and to reduce peak discharge of floodwater.”2 


5.1 Dam Sketch [April 2005] 
Each sketch for a dam shall include the following: 

.. Project Name – Name of project or the area being studied; 
.. Stream Name – Name of the studied stream; 
.. Location – Road name that crosses the stream; 
.. Date of survey; 
.. FEMA Contract Number; 
.. File name – Survey file name in the data collector; 
.. Surveyors – Names of those surveying, listed as last name, comma, first Initial. For 
example: Smith, J ; 
.. ERM ID – Specific location and type of benchmark (i.e. USGS benchmark disk on the 
upstream left headwall.); 
.. Elevation – Elevation of the ERM in the correct datum; 
.. North Arrow; 
.. Direction of flow; 
.. Top Width – Width of the top of dam; 
.. Side Slope – Embankment side slope of dam; 
.. Riser – size and material; 
.. Culvert Type – The type of culvert (i.e. concrete box, circular concrete pipe, elliptical 
metal pipe,); 
.. Number – Number of openings; 
2Encyclopædia Brittanica 2003, s.v. “dam (engin.).” 

N-28 Section 5.1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

.. Culvert hydraulic width – The distance that the stream flows through the bottom of the 
riser to the outlet pipe. If the culvert has a bend, this needs to be factored into the culvert 
hydraulic width. 
.. Spillway – Height and Width; 
.. Weir – Thickness of the weir where the water runs over; and 
.. Photo IDs and Location – Location and direction of where the photograph was taken. 
Place the circled photograph number where the picture was taken and an arrow in the 
direction the photograph was taken. 
Each sketch shall include both planimetric and profile view. The profile view should be oriented 
looking downstream at the structure. The sketches shall show the structure, channelbanks, 
channel, direction of flow, benchmark location, north arrow, dimensions, etc. A typical sketch is 
shown. 

Figure 26. Typical Earthen Dam Sketches 


N-29 Section 5.1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 27. Typical Dam with Riser Sketches 


5.2 Dam Survey Text File [April 2005] 
The text file must begin with two shots or entries that provide the program with a useful 
description of the structure. Shot number one provides that the type of structure, the abbreviated 
structure name, top width of the dam, and the side slope of the dam. For example, DAM DC3 14 

2.5 identifies the structure as dam (DAM) with the benchmark identification as DC3, the top 
width of the dam is 14, and the upstream side slope is 2.5. The second shot provides the name of 
the crossing road. 
N-30 Section 5.2 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

5.3 Dam Photographs [April 2005] 
A minimum of four digital photographs will be submitted for each dam. The required aspects or 
view of the photographs include: 

.. SOMEWHERE _USF. Standing upstream of structure, looking downstream at the 
structure; 
.. SOMEWHERE _USC. Standing on the structure, looking upstream at the pond or lake; 
.. SOMEWHERE_DSC. Standing on the structure, looking downstream at the channel; 
and 
.. SOMEWHERE_DSF. Standing downstream of structure, looking upstream at the 
structure. 
Figure 28. Examples of Dam Photographs 


5.4 Dam Survey [April 2005] 
It is the surveyor’s responsibility to identify what will interfere with or obstruct the flow of 
water. The survey should represent the hydraulic opening of all structures as well as surveying 
the top of road (the highest point to determine how high the water must rise to proceed over the 
road.) With a dam, the survey must locate the spillway and/or the opening of the riser as well as 
the pipes that go under the dam. The survey shall also include a downstream and upstream 
ground cross sections. 

Embankment and Top of Dam 

The embankment side slope is measured by taking the inverse of the rise/run. These are not 
required codes in the survey. Take two shots, one on top of the embankment and the other near 
the bottom perpendicular to the top of dam. Find the change in elevation and divide it by the 
horizontal distance, and then take the inverse. For example, if the change in elevation is 8 and the 
horizontal distance is 20 (8/21), the slope would be 0.4 and the inverse of the slope (1/x) would 
be 2.5. 

N-31 Section 5.3 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 29. Embankment and Top of Dam Shots 


The top of dam (TR) points defines the highest-grade line of the dam along the structure and the 
over banks. The survey of the top of dam shall begin, at a minimum, 100 feet down-station from 
the beginning of the dam and end, at a minimum, 100 feet up-station of the end of the dam, using 
the code TR. When going beyond the dam, the top of road survey must show how high the water 
must get to go over the extended road. The top of dam will not always be concrete or asphalt. 
Most dams will consist of vegetation or will be earthen. Shots shall be taken at breaks in 
elevation or at maximum 25-foot intervals. 

Ground Sections 

The upstream ground (GR) points shall represent the natural ground section as well as the water 
inverts of the pond or lake just off the dam. The ground section shall begin with the same station 
as the top of dam survey. The survey codes for the pond are GR (ground), CB (channelbank), 
TE (top and edge), and H2O (water). All dams must have two CBs, two TEs, and adequate 
number of H2O shots. The cross section across the pond should be surveyed at the bottom of fill 
of the dam and extend 100 feet beyond the channelbanks. The Channelbank (CB) is defined as 
the top of the pond’s bank. Top and edge (TE) of water is defined as the top of the water in the 
pond and where the water meets the land or the side of the channel. Water (H2O) is defined as 
the shots at the bottom of the streambed in the water. The amount of water shots taken depends 
on the size of the pond. 

Water Shots 

Surveying the water shots in the pond can be challenging. Most likely you will need a boat to 
take the water shots. For a successful shot, the pond needs to be very still as well as the boat. 

One method of surveying in the water is to take soundings. The first step is to mark off and 
number the stations on top of the dam. A minimum of 5 stations is recommended or every 50 
feet, and the spacing between stations should be no greater than 100 feet apart. Starting from the 
left at the TE looking downstream, mark off the first 50 feet with the number 1, the next 50 feet 
with a number 2, and so forth until it ends up near the right edge of pond (TE). 

Once all the stations are set, one surveyor walks on the top of the dam while two others survey 
the soundings in the boat. The surveyor on top of the dam will stand on the first station marked 

N-32 Section 5.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

number 1, while the boat takes a sounding in line with that station. The person(s) in the boat 
would extend the rod to the bottom of the pond and read the number where the rod meets the 
surface of the water. The surveyor on the dam will write those numbers in the notes and later 
subtract them from the elevation of the TE. 

If the pond is shallow, walking across with the rod is an option but beware of soft sediment. 
After acquiring the TE shot, extend the rod into the pond for a water shot. 

In the office, download the survey file and copy all the TRs with the numbers at the end and 
paste them at the end of the survey. Rename all the TRs with H2Os. Change the elevation of 
these shots to match the elevation in the notes. 

The following example shows sketches of the dam shots and a portion of a text format. 

Figure 30. Dam and Water Shots 


Figure 31. Portion of Text for Dam Shots 

4,919.3279,576.0364, 91.2530,TE 
19,928.7958,498.5637, 96.4390,TR 1 2.8 
20,992.8429,492.7395, 96.5600,TR 2 6.6 
21,1056.8358,493.0522, 95.6460,TR 3 5.8 
22,1122.2576,492.3201, 95.4070,TR 4 6.1 
23,1179.8873,494.5825, 95.3710,TR 5 6.6 
24,1267.0692,493.9005, 93.2310,TR 6 4.6 
25,1365.9968,496.0914, 91.2140,TE 
32,1379.4407,545.2858, 90.9540,H2O 
19,928.7958,498.5637, 88.4590,H2O 1 
20,992.8429,492.7395, 84.6300,H2O 2 
21,1056.8358,493.0522, 85.4560,H2O 3 
22,1122.2576,492.3201, 85.1570,H2O 4 
23,1179.8873,494.5825, 84.6510,H2O 5 
24,1267.0692,493.9005, 84.6510,H2O 6 

N-33 Section 5.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Downstream Sections 

The downstream natural ground section should be taken off of the fill or bottom of the slope of 
the dam and surveyed like an upstream section of a bridge or culvert. The codes for the 
downstream section of a dam are GR DS, CB DS, TE DS, and H2O DS. The DS codes the shots 
to be part of the downstream section of the survey. Omitting the DS would place those shots with 
the upstream ground section. 

Spillways 

If spillway is present, obtain elevation points of 
the top of dam (TR), top of spillway (TR TOP 
SPY1), bottom of spillway (TR BOT SPY1). If 
two spillways are present, spillway 1 would be 
on the left side of the dam while spillway 2 
would be on the right. Each spillway will have 
two TR TOP SPY# and two TR BOT SPY#. 
The example shown has a bridge that will not be 
surveyed. 


Figure 32. Spillway Shots 


Risers 

If a riser is present, obtain a surveyed shot at the top of the riser (RTOP 5 8). This shot is taken 
where the water goes over into the vertical pipe or box that allows the water to travel under the 
dam. The numbers following the shot are the dimensions of the top of the riser. These 
dimensions can be in any order (width, length). A circular pipe requires only one dimension. The 
bottom of the riser is coded RBOT. 

At the bottom of the riser there will be outlet pipes. These are coded the same way a culvert is 
coded. For example, if there are two circular pipes measuring 3 feet at the bottom of the riser, 

N-34 Section 5.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

they would be coded from left to right UIP1 3 and UIP2 3. The downstream outlet pipes also 
must be surveyed and given a code beginning with D (DIP1 3, DIP2 3). There will not be any 
downstream invert (DS IN) shot because of the downstream cross section. 

Figure 33. Shots Downstream of Dam 


There are other codes for the different types of risers. 
Some risers have orifices, which are small openings 
around the riser. These are to be surveyed if water 
would pass through these openings. These will be 
coded ORIF 2 1 along with the size of the opening 
(Height (2) and width (1), or the diameter). Each 
orifice along the riser must be shot and coded. Some 
risers will have a trash rack. A trash rack is a frame 
on top of a riser to prevent debris from entering the 
pipe. The shot shall be taken at the top of the trash 
rack and coded TRK 5 8 2.5 (width, length, height). 
A drainage valve needs to be shot and located within the survey. This code is VALVE and need 
to be surveyed on top of the valve. Not all dams have orifices, trash racks, or valves. The picture 

shown is of a trash rack and a valve. 

See codes for a dam on the following page. 


N-35 Section 5.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Table 3. Survey Codes for a Dam 

Valid Codes Example Note 
HEADER 
DAM ERM Top width SS DAM SC-3 20.0 2.5 
Shot 1 only. Dam with ERM ID, Top 
Width and embankment side slope (x.x: 
1) 
Road Name SR 2210, US220, Main Street Shot 2 only. 
FIELD SHOTS (Dam) 
ERM SF4, N_TAR-4 Elevation reference mark 
TR TR Top of Dam 
GR [DS] GR, GR DS Ground Field Data 
TE [DS] TE, TE DS Edge H2O 
H2O [DS] H2O, H2O DS Underwater Field Data Shot 
CB [DS] CB, CB DS Channel bank 
OPEN OPEN Open Area Field Shot 
BRUSH BRUSH High Brush Field Shot 
WOOD WOOD Wooded Canopy Field Shot 
ALPT ALPT1, ALPT2 Alignment points (left, right) 
FIELD SHOTS (Spillway) 
TR TOP SPY# TR TOP SPY1 Top of Spillway 1 (2 shots req.) 
TR BOT SPY# TR BOT SPY2 Bottom of Spillway 2 (2 shot min.) 
FIELD SHOTS (Outlet Pipes) 
UIB# Height Width UIB2 10.1 10.8 Upstream Invert Box 2 
DTE# Height Width Thick DTE3 5.6 7.9 0.5 D/S Top Ellipse 3 
DTP# DIA Thick DTP1 7.0 0.3 D/S Top Pipe 1 
D = Downstream 
U = Upstream 
I = Culvert Invert @ Centerline 
T = Top of Culvert @ Centerline 
B = Box, P = Pipe 
E = Elliptical Culvert 
FIELD SHOTS (Riser Barrel) 
RTOP DIA/Width [Length] RTOP 2.5, RTOP 3.7 6.1 Top of Riser Barrel (not trash rack) 
RBOT RBOT Bottom of riser 
ORIF DIA/Height Width ORIF 0.7 2.0, ORIF 0.5 0.0 Centerline elevation of orifice 
TRK DIA/Width Length Height TRK 5.1 8.1 2.0, TRK 4.5 0.0 1.5 Top of Trash Rack 
VALVE VALVE Location of drainage valve 

Codes having parameters with [ ] around them indicate that the parameter is not essential and can be left 
blank. However, leaving a parameter blank has implications. For example, the code RTOP 2.5 implies 
that 2.5 is a diameter of a riser barrel, therefore a length is not needed. The code GR in a dam survey 
implies that it is a ground shot on the upstream side of the dam, whereas GR DS shots apply to the 
downstream cross section. 

N-36 Section 5.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 34. Sample Survey Text File for a Dam 

D_ERT8A 
1,854226.635,2014210.168,538.110,DAM D_ERT8A 7 1.6 
2,854541.701,2014220.953,548.130,RUSSELL RD 
1001,854359.127,2013917.497,528.773,GR 
1002,854221.540,2013873.437,522.515,CB 
1003,854220.552,2013870.516,521.802,TE 
1004,854220.384,2013866.536,520.580,H2O 
1005,854221.212,2013863.021,518.909,H2O 
1006,854185.928,2013955.814,531.619,ALPT1 
1007,854183.787,2013950.116,531.408,TR 
1008,854170.179,2013920.233,529.331,TR 
1009,854166.790,2013904.698,521.478,TR 
1011,854135.941,2013826.498,523.818,TR 
1012,854121.788,2013809.822,521.702,TOP SS DS 
1013,854116.681,2013811.141,518.344,BOT SS DS 
1014,854137.223,2013819.301,523.211,TOP SS US 
1015,854139.662,2013818.914,521.994,BOT SS US 
1016,854122.593,2013775.640,523.685,TR 
1018,854097.596,2013669.724,523.609,TR 
1019,854088.427,2013624.651,523.605,TR 
1020,854086.453,2013614.915,523.010,TR TOP SPY1 
1021,854086.507,2013603.826,521.129,TR BOT SPY1 
1022,854085.908,2013599.391,521.153,TR BOT SPY1 
1023,854081.928,2013583.791,524.772,TR TOP SPY1 
1024,854068.253,2013531.177,526.146,TR 
1025,854059.871,2013486.784,528.146,TR 
1026,854059.631,2013485.519,528.578,ALPT2 
1027,854176.943,2013516.239,528.734,GR 
1028,854174.097,2013549.132,528.594,GR 
1029,854172.376,2013560.044,527.215,GR 
1030,854168.601,2013591.414,522.457,CB 
1031,854168.034,2013593.584,521.828,TE 
1032,854166.836,2013597.773,519.382,H2O 
1033,854147.625,2013611.644,517.086,H2O 
1034,854167.052,2013652.803,517.383,H2O 
1035,854173.637,2013711.759,512.080,H2O 
1036,854200.436,2013769.196,510.189,H2O 
1037,854212.550,2013823.456,513.170,H2O 
1038,853935.780,2013945.251,519.364,GR DS 
1039,853946.288,2013895.830,516.411,GR DS 
1040,853950.654,2013848.836,512.490,GR DS 
1041,853952.680,2013826.574,510.192,CB DS 
1042,853953.098,2013824.092,506.699,TE DS 
1043,853953.153,2013823.098,506.563,H2O DS 
1044,853953.360,2013821.460,506.564,H2O DS 
1045,853953.402,2013820.472,506.672,TE DS 
1046,853956.852,2013816.580,509.395,CB DS 
1047,853942.704,2013764.101,510.063,GR DS 
1049,853933.010,2013723.213,513.257,GR DS 
1050,853933.006,2013723.194,513.257,GR DS 
1051,853924.756,2013678.363,516.231,GR DS 

Except for the first two shots or entries, these shots can be in random order and do not need 
to follow this pattern as long as valid codes are used. A header or a structure ID is needed 
above the first shot. 

N-37 Section 5.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

6 Cross Section Survey 


6.1 Cross Section Sketch [April 2005] 
Each sketch for a cross section shall include the following: 

. Project Name - Name of project being studied; 
. Stream Name – Name of the studied stream; 
. Location – Nearest road intersection; 
. Date of survey; 
. FEMA Contract number; 
. File name – Survey file name in the data collector; 
. Surveyors – Names of those surveying, listed as last name, comma, first initial; 
. ERM ID - Specific location and type of benchmark (i.e. set in a telephone pole (# 43 
C 3887) with 2 guy wires and transformer.); 
. Elevation – Elevation of the ERM in the correct datum; 
. GPS location – can use hand held; 
. North Arrow; 
. Direction of stream flow; and 
. Photo IDs and Location – location and direction of where the photograph was taken. 
Place the circled photograph number where the picture was taken and an arrow in the 
direction the photograph was taken. 
Each sketch shall include both planimetric and profile view. The profile view should be oriented 
looking downstream. The planimetric view shall show where the cross section was surveyed. 
The sketches shall show the geometry of the cross section, ERM location, etc. A typical sketch is 
shown. 

N-38 Section 6.1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 35. Example of Cross Section Sketch 


N-39 Section 6.1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

6.2 Cross Section Survey Text File [April 2005] 
The text file must begin with two shots or entries that provide the program with a useful 
description of the cross section. The first shot number one provides the type of survey and the 
abbreviated structure name. For example, XS CCX1 identifies the structure as cross section (XS) 
with the benchmark identification of CCX1. The second shot provides the name of the nearest 
road, property owner, or any location descriptor. 

6.3 Cross Section Photographs [December 2004] 
A minimum of two digital photographs will be submitted for each cross section. The required 
aspects or view of the photographs include: 

.. XS_1_USC. Standing at the cross section, looking upstream at the channel; and 
.. XS_1_DSC. Standing at the cross section, looking downstream at the channel. 
Figure 36. Examples of Cross Section Photographs 


6.4 Cross Section Survey [April 2005] 
Each Mapping Partner will determine the location of the cross section. Refer to Appendix A of 
the Guidelines and Specifications for Flood Hazard Mapping Partners for methods to determine 
location. 

The survey may be done in state plane, depending on the project specifications. Alignment points 
(ALPTs) are required. 

The survey is similar to a cross section of an upstream face of a structure, but the survey will 
only extend approximately 50 feet past the channel banks. The survey of a cross section should 
always be oriented so that looking downstream, the survey stations would increase from left to 
right (Northing) and increase from downstream to upstream (Easting). 

N-40 Section 6.2 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Ground Sections 

The cross section shall represent the natural ground. The ground section should represent where 
the water would go once the water goes outside the channel. 

The stream channel is defined as the water being contained in the channel at normal levels. The 
survey codes for the stream channel are CB (channel bank), TE (top and edge), and H2O 
(water). All cross sections must have two CBs, two TEs, and adequate number of H2O shots. 
Channel bank (CB) is defined as the top of the stream channel. Top and edge (TE) of water is 
defined as the top of the water in the streambed and where the water meets the land or the side of 
the channel. Water (H2O) is defined as the shots in the water of the streambed. Water shots 
define the bottom of the channel. 

The number of water shots taken depends on the size of the channel. Water shots should be taken 
where there is a break in elevation in the channel. If the water is not clear, then probe the water 
to find any change in depth. There should be a minimum of three H2O shots. Two of those shots 
are at the bottom of the slope of the creek bed. If there is only one H2O shot in the middle of the 
creek, the representation of the channel would look like a “V”. More H2O shots will be needed 
based on the size of the channel. 

N-41 Section 6.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Table 4. Survey Codes for a Cross Section 

Valid Codes Example Notes for use 
HEADER 
XS BM XS CCX1 Shot 1 only. Cross Section with 
Benchmark 
Road Name New road off Stowe Road Shot 2 only. 
FIELD SHOTS (Cross Section) 
ERM ERM CCX1 Elevation reference mark 
GR GR Ground Field Data 
TE TE Edge H2O 
H2O H2O Underwater Field Data Shot 
CB CB Channelbank 
OPEN OPEN Open Area Field Shot 
BRUSH BRUSH High Brush Field Shot 
WOOD WOOD Wooded Canopy Field Shot 
ALPT ALPT1, ALPT2 Alignment points (left, right) 

Figure 37. Sample Survey Text File for a Cross Section 

CCX_WA233 
1,763755.1600,2057543.8200,289.95,XS CCX_WA233 
2,763755.1600,2057185.2000,290.53,CCX_WA233. 
3,763755.7242,2057202.7587,288.99,ALPT1 
3,763755.7242,2057202.7587,288.99,GR 
4,763755.9892,2057176.0401,290.56,GR 
5,763757.0299,2057170.3985,288.69,GR 
6,763757.1382,2057166.8245,285.40,GR 
7,763759.5638,2057159.2319,284.14,CB 
8,763759.0692,2057151.3914,281.47,GR 
9,763759.1727,2057145.0171,277.39,TE 
10,763759.3727,2057142.5860,274.83,H2O 
11,763759.5044,2057129.5670,274.30,H2O 
12,763759.7048,2057114.9193,276.17,H2O 
13,763759.0849,2057112.1385,277.53,TE 
14,763757.2932,2057105.4344,281.61,GR 
15,763757.1510,2057097.7461,284.52,CB 
16,763757.4565,2057083.2396,284.56,GR 
17,763756.8081,2057075.8987,287.16,GR 
18,763755.1600,2057061.3327,281.91,GR 
18,763755.1600,2057061.3327,281.91,ALPT2 

Except for the first two shots or entries, these shots can be in random order and do not 
need to follow this pattern. A header or a structure ID is needed above the first shot. 

N-42 Section 6.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

7 Overview and Problem Surveys 

7.1 Overview Survey [April 2005] 
For an overview survey, survey two cross sections, the geometry of the top of road (TR) and the 
upstream ground section (GR) with the streambed between channel banks as well as the structure 
shots. Shots can be in any order. The survey should run along the line of the backsight or the 
alignment points (ALPT). 

The ground section will be taken at the bottom of the fill of the structure. 

The survey file will allow for the creation of three data sections: top of road section, field 
(ground) section, and structure data block. Only the TRs, BEGIN, END, and RAIL shots will 
be part of the top of road data. Only the GRs, CBs, TEs, and H2Os will be part of the ground 
section. The TOEs, Piers, culvert inverts, and downstream inverts are part of the structure data 
block. 

Other codes such as ERM (benchmark), ALPTs, and GPS shots are needed for the survey. Do 
not take a GR shot on top of the road. Below is an example of a top of road shot being coded as a 
GR, which results in an incorrect ground section. 

Figure 38. Example of Top of Road Shot Coded Incorrectly as GR 


The survey should be looked at in a profile view rather than a planimetric view. Below is an 
example of a profile view. The green line represents a ground shot (GR) surveyed in the field. 
The top line represents the top of road. The rail is represented by the code RAIL and will be 
added to the top of the road elevation where the rail shot was taken. The area in the middle of 
this view is the trapezoidal opening of the structure. This represents what the creek will pass 
through. The gray represents the fill or the blockage. The vertical lines are the piers and the red 
dots are the channelbanks. 

N-43 Section 7.1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 39. Profile View of Overview Survey 


Below is a planimetric view of a bridge structure. This shows that all shots do not have to be 
directly on a base line. The TRs are in the center of the road due to the crown being higher than 
the edge of pavement. If the top of road is higher on the downstream side, then survey the TRs 
along that baseline. Trees, branches, telephone poles, and road signs can get in the way of the 
survey which cause the ground shots to not be in a straight line. The example below shows that a 
GR shot can be moved horizontally to allow for an easier shot as long as the shot doesn’t change 
vertically. Also, all the CBs, TEs, H2Os, DS IN, TOEs, and pier shots were taken from the top of 
the bridge. 

Figure 40. Adjusting Problem Bridge Shots 
N-44 Section 7.1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 

Updated May 2005]

7.2 Channel Shots [April 2005] 
There should be a minimum of three H2O shots. Always, two of these shots are at the bottom of 

the slope of the creek bed. If there is only one H2O shot in the middle of the creek, the 

representation of the channel would look like a “V”. To the left is an example of one H2O. More 

H2O shots will be needed based on the size of the channel. H2O shots should be taken at the 
upstream face of a structure. 

Figure 41. Types of Channel Shots Below are two types of channels. The drawing to 
the left has two CBs, two TEs, and three H2Os. 
Notice two of the H2O shots are at the edge of the 
channel bottom. The drawing above only has one 
and shows a poor representation of the channel. 
The TEs determine the stream centerline. It is 
critical for those shots be taken at the inside edge 
of the channel. The drawing on the right has a dry 
channel. Two TEs are required in a survey to 
determine the centerline and shape of the channel. 
The shot in the middle of the channel is a GR since 
there is no water. Water shots (H2O) are not 
always needed. There will be times when there 
could be a GR between a CB and a TE. 


Figure 42. Two Types of Channels 


7.3 Skewed Streams [April 2005] 
Skewed streams are not perpendicular to the structure. All skewed streams are unique. For a 
culvert, all the TE’s, CB’s, and H2O’s will be taken near the opening of the structure. When 
surveying a skewed stream for a bridge, survey the ground and channel section in line with the 
bottom of fill. The channel section will not be lined up with the channel at the structure. 

N-45 Section 7.2 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Remember, the back sight should remain parallel with the road while trying to keep ground and 
channel section in line with the structure. 

There will be special situations that the survey needs to be translated to align the top of road with 
the GR section in the office. The adjustment needs to be made to the top of road section. Bring 
the survey data into Autocad or Microstation and translate the TR section to line up with the GR 
section. The channel section of the ground section should align with the opening of the structure. 

Figure 51 shows two examples of skewed bridges. Bridge # 1 is skewed but the angle of the 
water entering the bridge is 90 degrees. The stream flows through the piers. Bridge # 2 is also 
skewed but the angle of the water entering the bridge is at ~ 55 degrees. This angle must be 
written on the survey drawing template. This means the piers are acting wider than their actual 
size. The actual pier width should be recorded. 

Figure 52 is a diagram of a skewed culvert. The baseline is created by the alignment points 
(ALPT). All the TRs will be part of the top of road baseline and all the GRs, TEs, CBs, and 
H2Os will be part of the ground section baseline. The diagram explains what happens to the 
survey points. Notice the left TE (top and edge of water) is not inside the culvert and the right 
CB (Channelbank) is in between Box 2 and 3. This will enclose box three with sediment and 
give a false survey. Culverts do not require a skew angle. 

Figure 43. Skewed Bridges 

Figure 44. Skewed Culvert 


N-46 Section 7.3 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Below are two HEC-RAS examples of a poor alignment and the correct alignment. 

Figure 45. Poor and Correct Alignment of Skewed Culvert 


7.4 State Plane Coordinates 
State plane coordinates must be used rather than assumed coordinates. Two extra codes need to 
be taken to allow the alignment of the survey to be perpendicular to the stream. The codes are 
ALPT1 (station alignment point 1) and ALPT2 (station alignment point 2). When both ALPT1 
and ALPT2 are present, they define a stationing baseline for all the shots. ALPT1’s station will 
be 1000 by default. ALPT1 should be left of ALPT2 looking downstream. 

The purpose of these codes is to eliminate the need to align the total station parallel to the 
structure or cross section to capture the station in the northing coordinate. The ALPT codes 
establish a stationing axis that can be used to calculate station for all other shots. 

Figure 46. Codes for State Plane Coordinates 
N-47 Section 7.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

7.5 Super-Elevated Curves 
Super-Elevated Curves refer to bridges or culverts on these sections of road. The top of road 
section will be taken at the highest elevated side of the road. The deck thickness is measured as 
the distance between the BEGIN (at highest elevated road) and the deck at the lowest side of the 
bridge. For example, if the highest elevated road (upstream) is at an elevation of 100 feet and the 
lowest elevated road (downstream) is at 97 feet with a measured deck of 4 feet. To find the 
correct deck thickness, calculate the difference between the two road elevations (3 feet) and 
adding the deck (4 feet), which makes the deck 7 feet. This means that when the high water 
reaches the bottom of the deck, the water will need to go 7 feet until it goes over the road. This is 
to determine two things: how high does the water have to get to go over the road and how low is 
the actual deck (top of the trapezoid). Shooting the low chord (LC) is another way to determine 
the deck thickness. 

7.6 Relief Structures 
A Relief structure is defined as a structure that will give relief to the main channel, still allowing 
floodwater to pass under the road. The relief structure will allow any water to pass through the 
structure before it will reach the top of road. A relief structure can be another stream that may 
merge with the studied creek downstream, or a bridge or culvert. The relief structure must also 
be part of the stream’s flood plain. 

If it appears that the floodwaters will overtop the road before they pass through the relief 
structure, the relief structure is not be surveyed. For example, if the water is rising to flood 
levels, will that relief structure be used before the water floods over the road? 

A relief culvert must be 3 feet in diameter or greater. Relief culverts will be numbered from left 
to right. The channel codes for the relief structure will require a GR in front of them (GR CB, 
GR TE). The survey can only have two channel banks and two top and edges. This allows the 
shots to be coded within the ground section. Two side-by-side bridges will require two BEGINs, 
ENDs, and TOEs. Those bridge shots will need either a 1 or 2 after those shots (BEGIN 1, 
BEGIN 2, etc). The relief channel code shots will need the GR in front of the codes similar to 
the culvert. Since there will be two or three structures surveyed, there will be two or three 
downstream inverts (DS IN). Place a 2 or 3 after each DS IN but do not place a 1 after the main 
structure. Keep the shots for each structure together in the survey. 

See the following examples of relief structures. 

N-48 Section 7.5 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Figure 47. Relief Structures 


Upstream and Downstream Face of Structure 

The USSTRUCT / DSSTRUCT codes are required as they measure the hydraulic width of the 
structure. The shots are to be taken on top of the bridge at the upstream (USSTRUCT) and 
downstream (DSSTRUCT) face of the structure over the stream. Using these codes will overwrite 
the existing hydraulic width value found in the first shot. For a Culvert, these shots will be 
taken at the middle culvert. 

[September 2004]

 Table 5. Optional Survey Codes for Structures and Cross Sections 

Valid Codes Example Note 
DSSTRUCT (structures only) DSSTRUCT Downstream face at C/L of stream 
USSTRUCT (structures only) USSTRUCT Upstream face at C/L of stream 
ALPT1 ALPT1 Station Alignment Pt. 1 (left d/s) 
ALPT2 ALPT2 Station Alignment Pt. 2 (right d/s) 
BM BMid BM GPS051 Horizontal and vertical control pt. 

N-49 Section 7.5 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

Notes about Optional Survey Codes 

When both ALPT1 and ALPT2 are present, they define a stationing baseline for all the shots. 
ALPT1’s station will be 1000 by default. ALPT1 should be left of ALPT2 looking downstream. The 
purpose of these codes is to eliminate the need to align the total station parallel to the structure or 
cross section alignment in order to capture the station in the northing coordinate. Using these points 
requires reduction to get the station of the shots. If the user anticipates having to adjust the stations 
of some of the points (typical for a skewed structure), then this option is not recommended. 

The presence of two BM codes allows for complete translation and rotation of the shots into the state 
plane coordinate system provided the benchmarks’ XYZ locations are available. 

The first benchmark encountered in the file is assumed to contain the most accurate horizontal and 
vertical positioning. The second BM is only used for rotation and for checking the real world 
coordinates. A difference greater than 1.0 feet in the horizontal distance between the BM shots and 
the true state plane coordinate distance will be flagged as a problem. If only one BM code is 
provided, the survey will be translated, but not rotated. 

N-50 Section 7.5 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

8 Approximate Survey [April 2005] 

The survey measurements for approximate 
structures shall be taken on the upstream side 
of the structure. The hydraulic opening shall 
be measured using a level rod, survey wheel, 
wooden foldout ruler, and a hand level. 
Elevation will be referenced to the highest 
point on the road at the structure. The vertical 
datum for all hydraulic structures will be 
interpolated from the digital elevation model. 

Channel inverts, channel bank elevations, 
and deck measurements will be referenced to 
the top of crown. The channel measurements 
shall be taken at the upstream face of the structure. Channel top width, channel bottom width, 
channel bank elevation, and the invert are the four measurements that are needed for the channel. 


All measurements are to be rounded to the nearest foot except channel height, deck thickness, 
and culvert dimensions. Data will be entered into a GIS point coverage or shapefile showing the 
location and the attributes for structures surveyed for approximate or limited detailed studies. 

8.1 Digital Photographs [April 2005] 
One photograph will be taken at looking at the upstream face of each structure. The photograph 
shall represent the channel, top of road, and the structure. If the upstream face is unattainable, the 
photograph can be taken at the downstream face and with a note in the comments field. 

Figure 48. Example of Approximate Survey Photograph 


N-51 Section 8.1 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

8.2 DOT Bridge Survey Reports Recon [April 2005] 
DOT Bridge Survey Reports (BSR) and Culvert Survey Reports (CSR) may be used to gather 
survey data for the approximate structures. The BSRs and CSRs could be filed with the Bridge 
Maintenance Unit or the Hydrology Department. County maps with the BSR and CSR numbers 
can be found digitally at the DOT website or order them with the Bridge Maintenance Unit. The 
DOT county structure number shall be part of the GIS point coverage. 

Figure 49. DOT Bridge Survey Report 


8.3 Approximate Bridge Survey [April 2005] 
A trapezoidal opening with the low cord, number of bents and widths, and hydraulic width of 
bridge will represent the bridge. 

The channel measurements shall be taken at the face of the bridge. 

The bridge will be surveyed by measuring the following: 

.. Deck thickness - distance from top of crown of road to low cord (bottom of bridge at 
opening); 
.. Top width – Distance between the top abutments (BEGIN and END); 
.. Toe width - Bottom of Abutments - Distance between the bottom abutments (TOES); 
.. Hydraulic width – Distance between US face and DS face of bridge (Outside to Outside); 
.. Number of piers; 
.. Pier width; 
N-52 Section 8.2 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

.. Invert – Distance between the US bottom of channel and the crown of road; 
.. Channel top width – Top width of channel from channel bank to channel bank at 
structure; 
.. Channel bottom width – Bottom width of channel at the structure; and 
.. Channel bank elevation – distance from top of crown of road to the channel bank. 
Figure 50. Approximate Bridge Survey 


Figure 51. Hydraulic Width of Bridge 


8.4 Approximate Culvert Survey [April 2005] 
Culverts will be represented by the actual barrel dimension obtained from the survey. The four 
types of culverts are Arch, Box, Circular, and Elliptical. The rise (height) and Span (width) will 
be measured at all culverts with the exception of circular culverts, which only need the rise. The 
channel measurements shall be taken at the face of the bridge. A hand level is suggested on 
determining the channel invert. 

N-53 Section 8.3 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

These fields will be part of the approximate culvert survey: 

.. Number of Barrels – Number of Boxes, Circular pipes, or Elliptical pipes; 
.. Shape or Culvert type – Box, Circular, or Elliptical; 
.. Rise – Height of Culvert or Diameter for a circular culvert; 
.. Span – Width of Culvert; 
.. Hydraulic width – Distance between US face and DS face of culvert; 
.. Upstream Invert – Distance between the US bottom of channel and the crown of road; 
.. Channel top width – Top width of channel from channel bank to channel bank at 
structure; 
.. Channel bottom width – Bottom width of channel at the structure; and 
.. Channel bank elevation – distance from top of crown of road to the channel bank. 
Figure 52. Approximate Culvert Survey 


Figure 53. Hydraulic Width of Culvert 


N-54 Section 8.4 


Guidelines and Specifications for Flood Hazard Mapping Partners [April 2004; Sections 
Updated May 2005]

9 Historical High Water Marks [April 2005] 

All streams must have at least two high water 
marks from different storms. To get this 
information, ask neighboring landowners if they 
have witnessed a major storm or hurricane. The 
surveyor may need to research to help the residents 
remember what years each hurricane came through 
the area. 

The witness shall determine the precise location of 
the historical high water mark as well as the date 

Hurricane Floyd and/or year. If the witness can recall more than one 
storm, survey each location and use the code (HIS) 
with the year or storm after the code. 

Each set of notes for a historical shall include a historical title page. The historical title page shall 
include the following: 

.. Stream name; 
.. The name of the interviewer; 
.. The name of the witness; 
.. The witness’s address; 
.. How long the witness has lived there; 
.. Date of interview; 
.. What type of high water events occurred? Ex. Heavy rain, Hurricane; 
.. How often; 
.. Location of high water mark. Be very descriptive and use distances from landmarks. Ex. 
oak tree, fence, house, and stream); and 
.. Any other types of comments. 
After the interview, be sure to ask the owner for permission to survey on the land. Survey to find 
the elevation of the high water mark. 

Figure 54. Sample Sketch for Historical Flooding Survey 


N-55 Section 9