Hydrology Documentation

3.2 HYDROGRAPHY--MAJOR CODE 050

Flowing and standing water and manmade features directly related to hydrography are collected in this category.

3.2.1 General Principles

Coding Principles

The majority of codes apply to both topographic and topographic- bathymetric editions, but some codes only apply to topographic- bathymetric editions. The individual coding descriptions identify these codes. If a feature appears on a topographic edition and the coding description indicates that it applies only to topographic-bathymetric editions, do not collect the feature.

The term "water body" is used to refer to any hydrographic feature collected as an area as well as any areola hydrographic feature collected as a degenerate line or as a node because of its small size. Use is not limited to a lake or a pond.

All double-line streams are digitized as areas. Where double- line streams join other water bodies or other double-line streams the two features are separated from one another by closure lines.

If a hydrographic feature is less than or equal to 0.030 inches in length (regardless of map scale), it is collected as a degenerate line or node; no shoreline code is added.

Do not collect islands that are less than or equal to 0.030 inches in length (regardless of map scale), unless they are named.

Feature Classification and Delineation

In the real world, hydrographic features vary considerably. The treatment of these features on USGS maps also varies considerably, making determination of the appropriate code difficult in some cases. In many cases, symbol references provide only a general idea of what a feature may look like. It is necessary, when collecting hydrographic features, to pay attention to such things as shape or form, context within the map, names, labels, and marginal information, some or all of which may be important aids to classification. Generally, use the code that best describes the feature, even if the symbolization of that feature varies from the symbolization that is referenced.

Lakes are defined as standing bodies of water with predominantly natural shoreline. Reservoirs are constructed basins formed to contain water or other liquids for various purposes. The names and labels of these features do not always convey the proper classification, and care must be taken not to use names and labels alone in determining how to classify them. Many features that are known as "Reservoirs" or labeled on the graphic as "Reservoir" may in fact, be lakes or ponds. As a general rule, if a water body has a regular geometric shape or other information indicates it is contained by a constructed basin, then it is a reservoir. If it does not appear to be contained by a constructed basin, then it is a lake or pond.

Many constructed reservoirs found on the map can be coded according to their specific type. Individual codes exist for covered reservoir, salt evaporator, aquaculture pond, industrial water impoundment, sewage disposal pond, tailings pond, soda evaporator, and filtration pond, all of which are types of reservoirs. The code for reservoir (050 0101) is used only when no other specific attribute code is available to describe the type of reservoir. Swimming pools and nonwater reservoirs are collected in the Manmade Features category.

Where a stream or river has been dammed, use the following guidelines in determining whether to collect the water body above the dam as stream or lake.

o Collect the water body as stream if it retains its river-like appearance, and the width of the water body above the dam is similar to the width of the water body below the dam. Many rivers have been dammed to maintain water levels for navigation, or for flood control, in which case there is commonly a series of dams on the river.

o Collect the water body as lake if it is actually an impounded water body created by the dam, and the width of the water body above the dam is significantly greater than the width of the water body below the dam. If a submerged river is shown within an impounded lake, collect both a lake and submerged stream.

To determine whether a given feature should be collected as a stream or as a ditch or canal, use the appearance and location of the feature. Do not rely only on names and labels, because in some regions of the country the term ditch is used as a synonym for creek. Ditches and canals have regular geometric shapes and are cut through land to provide irrigation or drainage, and for navigation around obstacles or between water bodies. If contours have been turned upstream and dropped at a hydrographic feature, as in symbols 312(A), 532.8(C), or 2302.07(D), or if the feature parallels a contour and has little or no gradient, collect the feature as a ditch or canal. Streams are naturally occurring, do not have a regular geometric form, and normally have a gradient and flow downslope. Streams that have been relocated or altered for purposes other than drainage or irrigation are considered to be streams and not ditches. In some cases, only a portion of a stream has been realigned, and the purpose of that realignment cannot be determined from the map. Unless the realigned portion is identified by a ditch label, or a change in name to a named ditch, collect it as a stream. Streams that have been channelized or canalized for navigation (the Ohio and Mississippi Rivers, for example), are collected as streams and not canals, even though a set of locks and dams may have transformed portions of the river from a free-flowing water body to a series of slack water pools.

Hydrographic features form networks where large and small rivers, streams, lakes, ponds, and so on, flow in and out of each other. On the map, these networks appear as blue areas with no dividing lines. However, in collecting digital data, each part of the network must be classified as the appropriate feature and assigned a code. What the feature is and where it begins and ends is not always clear. The following guidelines can be used to help make these determinations:

o There are cases where it is difficult to classify the "bumps" or "fingers" of water bodies. Where a single-line stream appears to widen as it enters a double-line stream or lake, a judgement must be made as to whether the widened area is part of the double-line stream or lake (a "finger" in the larger water body that extends to the single-line stream) or if the single-line stream has widened to a double-line stream, which then enters the larger water body (double-line stream or lake). As a general rule, lakes tend to have many "fingers" and most of the time these are considered to be part of the lake. A single-line stream usually enters a lake without becoming a double-line stream. However, "fingers" on a double-line stream are usually part of the incoming stream. In both cases, the length and width relationship of the incoming water body must be taken into consideration. If it is longer than it is wide, or has a narrow neck, it may be considered as a separate incoming feature from the single-line stream.

o A single-line stream may flow into something other than a double-line stream, which then connects to the larger water body. Determine the feature based on shape, size, and positioning of the feature. For example, a single-line stream may flow into a partial oxbow (lake or pond) that connects to a double-line stream. Each of these three features is collected as an individual feature.

o Where a "finger" occurs in a water body, whether there is an entering stream or not, the overall size and the size of the opening neck are criteria that can be used to decide if it is part of the larger water body or not. Generally, the larger the size of the "finger" and the more narrow the neck, the more likely it is to be a separate, and possibly different, feature.

o Whether a widened portion of single-line stream is collected as a small lake or as a double-line portion of the single-line stream, is dependent on its relative width, shape (linearity versus roundness), and name. Use judgement and common sense in determining whether you have a lake or a stream.

o The "fingers" on impounded water bodies are considered part of the impounded water body up to the point where the entering stream returns to its normal channel. The normal channel of a stream can be recognized by its fairly consistent width or may be indicated on the map by the previous stream bed or contours.

o Name is not always an indicator of the feature classification and should be used only in conjunction with other criteria.

o In all cases, use your knowledge of what these features look like on the ground, along with your best judgement and common sense. Recognize that there may not be a single "right" way of delineating and coding connecting water bodies; several different solutions may all be equally "correct."

The classification of some hydrographic features added during photorevision cannot be determined solely on symbology, because earthen and manmade shoreline are both shown in purple, and the intermittent nature of features cannot always be determined from photography. Classification of these features must, therefore, be based on context. If photorevised shoreline has a regular, geometric shape or similar nearby shoreline is shown as manmade, or both, collect the shoreline as manmade. If in doubt, collect the shoreline as earthen (050 0200). In deciding whether or not to collect a feature as intermittent, look at the overall drainage pattern in the area. Hydrographic features are only collected as perennial if there is little doubt that they contain water year round; if uncertain, collect them as intermittent.

Flow Direction

The direction of flow is indicated on the map by the contours and the overall pattern of the drainage network. Information on the flow of water bodies is collected to support data users who model network flow on hydrographic phenomena for scientific studies. Flow is coded in one of two ways in the DLG data. For double-line features, the descriptive attribute codes for right bank (050 0605) and left bank (050 0606) are applied. For single-line features, the node attribute codes for upper origin (050 0001), upper origin at water body (050 0002), sink (050 0003), entering water body (050 0004), and exiting water body (050 0005) are applied.

For double-line features, capture the direction of flow by theoretically looking downstream and indicating right and left bank. For streams that have complex channels or islands, apply right and left bank codes to the outermost double-line channel, so long as the outermost channel can reasonably be considered to be a diverging and converging channel of the stream. Remember that the stream must maintain a roughly linear shape. The shore of any land area between the right and left banks is collected as shoreline.

In some areas, adjoining quadrangles must be consulted in order to determine direction of flow.

Node codes and right and left bank codes are only used when flow can readily and confidently be determined from the topography and overall pattern of the drainage network as shown on the map. Do not spend more than a few minutes looking for indications of direction of flow. If in doubt, do not code flow. Usually the direction of flow of streams and ditches in very flat areas, and of ditches in arid areas, cannot be determined unless contours cross the feature, the feature connects up with water bodies for which elevations are shown, or flow arrows are shown on the map. In coastal areas where flow cannot be determined, the gut code (050 0122) may be applied to water between the lowest contour and the open sea.

3.2.1.1 Node Attribute Codes

Node attribute codes assist in determining the direction of water flow of single-line hydrographic features. Node attribute codes are not used at the origin of double-line hydrographic features, or where double-line hydrographic features enter or exit water bodies. They are, however, used where single-line hydrographic features enter or exit double-line hydrographic features, including where single-line hydrographic features widen to, or narrow from, double-line hydrographic features.

3.2.1.2 Area Attribute Codes

In a structured file, it is not necessary to explicitly code the line around an area unless the line itself has characteristics that must be described. However, USGS maps have traditionally described characteristics of the limits of some hydrographic features. This includes whether a shoreline is earthen (blue) or masonry (black), and whether or not it can be accurately located (dashed versus solid). (The limits of a perennial versus intermittent stream or lake have also been symbolized differently. However, because it is the lake or the stream that is perennial or intermittent, that information is explicitly encoded on the area, rather than on the shoreline.)

Where the characteristics of a line around a hydrographic feature can vary, the line is always attributed. For example, sewage disposal ponds may have earthen shorelines (blue) or they may have masonry shorelines (black). Therefore, the line around a sewage disposal pond must always be attributed. Sometimes, however, the line around a hydrographic feature is simply a symbol, and it is collected as an unattributed line and the line symbology is derived from the area code. For example, the blue lines around evaporators, cranberry bogs, duck ponds and the like have been described as being "ditches." However, on the ground, the limits of these features are in some cases ditches, in some cases embankments, and in some cases ditches on embankments. The blue line on the map shows the extent of the hydrographic feature, but does not describe any characteristics of the line; the line is, therefore, unattributed. Please note that although in the past aquaculture ponds, filtration ponds, and industrial water impoundment have been shown with either earthen shorelines (blue) or masonry shorelines (black), the distinction is no longer considered important, and in the future these features will always be outlined in black; the line is, therefore, unattributed.

Where the outline of a water body is attributed, the entire outline is attributed. Although the shoreline may be interrupted by a manmade structure, which is collected either in this category or in the Manmade Features category, the line of contact between a water area and a land area is always also collected as some type of shoreline.

Appendix 3.2.A provides unambiguous information on the attribution of the outlines of hydrographic features collected as areas. In general, if the outline of the feature is always shown on the map with the same symbology, the line is unattributed because it is in essence a symbol. Follow these guidelines even if an individual feature on a map is outlined using a nonstandard symbol. In some cases, the outlines of two hydrographic features may coincide, so the instructions for coding of the outlines of both features must be considered. Also, if part of the outline of an area is formed by another hydrographic feature, that portion of the outline is collected as that feature.

Additional hydrographic features can exist within a larger hydrographic feature. This is most common in a bay, estuary, gulf, ocean, or sea, or a gut, but can also occur in a lake, or a double-line stream or canal. Even though the additional features can be collected as areas, the integrity of the larger hydrographic feature is not affected. All areas within a larger hydrographic feature receive the code of the larger feature and their own code or codes. This includes areas that are created by linear features that close, and features collected as areas. An exception to this general principal is any area where the blue water tint has been cleared; some flats (see code 050 0115), some channels (see code 050 0419), spoil area, dredged area, or dump area (050 0424), and holiday area (050 0426).

3.2.1.3 Line Attribute Codes

Line attribute codes are used only where specific characteristics of a line that surrounds an area must be described. Unlike general purpose attribute codes, line attribute codes apply to features that can only be collected as a line.

USGS maps use line symbology to distinguish between earthen shorelines (blue) and manmade shorelines (black) and to describe the accuracy of the location, definite (solid line) versus indefinite (dashed line). There are unique codes to collect these characteristics: 050 0200 for earthen definite shoreline; 050 0201 for manmade shoreline; 050 0203 for earthen indefinite shoreline. Apparent shoreline (050 0207) is a special type of indefinite shoreline shown only on topographic-bathymetric editions. The descriptive attribute codes for right bank (050 0605) and left bank (050 0606) are used instead of the earthen definite shoreline code (050 0200) on double-line features where flow is collected. For all other shoreline characteristics, the right bank and left bank codes are used in addition to the appropriate shoreline code.

Additional line codes are used to collect other hydrographic features symbolized on the map, for example, Carolina bays (050 0205) and limiting danger lines (050 0206). Closure lines (050 0202) are used to code lines that are not shown on the map and must be added to the DLG.

Where no specific information is required to describe characteristics of the line, an unattributed line is collected. Unattributed lines can be collected regardless of whether an area feature has a symbolized perimeter or not. If the perimeter of an area is always symbolized in a particular way, the line symbol can be derived from the area feature and no specific line coding is required.

A closure line is used where it is necessary to separate polygons that represent different hydrographic features when the separation is not explicitly indicated on the graphic. For example, in order to separate a stream polygon from a lake polygon, a closure line is collected where the double-line stream enters the lake.

Closure lines are required whenever flow is collected from one water body to another. For example, a closure line is collected where a double-line stream flows into another double-line stream and left bank and right bank are collected to indicate flow. Closure lines between like features are not necessary when flow is not coded. For example, no closure line is collected where two sections of double-line ditch connect with one another, if the direction of flow cannot be determined and the banks of both sections of ditch are coded as shoreline or manmade shoreline rather than left bank and right bank.

Closure lines are not used to close small gaps in linear features where the symbology has been broken on the map, although they have been used in this way in the past. In most cases, the symbology has been intentionally broken, because the feature is not visible on the earth's surface. In particular, map editors took great care to ensure that the dash and dot pattern of an intermittent stream, symbol 405(A), was adjusted to clearly indicate stream junctions. For example, editors made sure that intermittent streams started, and joined other streams, with the dash portion of the symbol, and that the dot portion of the symbol did not occur at sharp bends or other places where it might be confusing. If a gap is clearly the result of a scribing or registration error, and not an intentional break in the symbology, then the gap is ignored and the hydrographic feature is collected as a continuous line through the gap.

The closure line code is not assigned to the line segment digitized across the gap created where the symbol for an underpassing feature is broken back from the symbol of an overpassing feature, although it has been used in this way in the past. Instead, the line segment is assigned the underpassing code (050 0617) and the code or codes of the hydrographic feature.

If a feature collected as an area is intermittent, the intermittent code (050 0610) is applied only to the area, not to the line that bounds the area.

See section 3.2.1.2 on Area Attribute Codes for when to apply a line attribute code and when to collect an unattributed line around a specific area. See the description for closure line (050 0202) for more information on the use and placement of these lines.

3.2.1.4 Single-Point Attribute Codes

There are no general principles that apply to the single-point attribute codes.

3.2.1.5 General Purpose Attribute Codes

Hydrographic features that are symbolized as single-line are collected as lines, whereas features that are symbolized as double-line are collected as areas.

3.2.1.6 Descriptive Attribute Codes

There are no general principles that apply to the descriptive attribute codes.

3.2.1.7 Parameter Attributes

The descriptive attribute codes for right bank (050 0605) and left bank (050 0606) are used instead of the earthen definite shoreline code (050 0200) on double-line features where flow is collected. For all other shoreline characteristics, the right bank and left bank codes are used in addition to the appropriate shoreline code.

3.2.1.8 List of Hydrography Attribute Codes

o Node attribute codes

050 0001 Upper origin
050 0002 Upper origin at water body
050 0003 Sink
050 0004 Entering water body
050 0005 Exiting water body

o Area attribute codes

000 0000 Outside area
050 0100 Alkali flat
050 0101 Reservoir
050 0102 Covered reservoir
050 0103 Glacier or permanent snow field
050 0104 Salt evaporator050 0105 Inundation area
050 0106 Aquaculture pond
050 0107 Industrial water impoundment
050 0108 Area to be submerged
050 0109 Sewage disposal pond
050 0110 Tailings pond
050 0111 Marsh, wetland, swamp, or bog
050 0112 Mangrove area
050 0113 Rice field - Code Deleted
050 0114 Cranberry bog
050 0115 Flat (tidal, sand, gravel, mud, etcetera)
050 0116 Bay, estuary, gulf, ocean, or sea
050 0117 Shoal
050 0118 Soda evaporator
050 0119 Duck pond
050 0120 Void area
050 0121 Obstruction area in water area
050 0122 Gut
050 0123 Dry-dock chamber
050 0124 Filtration pond
050 0125 Foul ground
050 0126 Mine danger area

o Line attribute codes

050 0200 Shoreline
050 0201 Manmade shoreline
050 0202 Closure line
050 0203 Indefinite shoreline
050 0204 Apparent limit - Code Deleted
050 0205 Outline of a Carolina bay
050 0206 Limiting danger line
050 0207 Apparent shoreline
050 0208 Sounding datum
050 0209 Low-water line
050 0210 Airboat trail
050 0299 Processing line

o Single-point attribute codes

050 0300 Spring
050 0301 Nonflowing well
050 0302 Flowing well
050 0303 Riser
050 0304 Geyser
050 0305 Windmill
050 0306 Cistern - Code Deleted

o General purpose attribute codes

050 0400 Rapids
050 0401 Falls
050 0402 Gravel pit or quarry filled with water - Code Deleted
050 0403 Gagging station
050 0404 Pumping station
050 0405 Water intake
050 0406 Dam or weir
050 0407 Lock chamber
050 0408 Spillway
050 0409 Gate
050 0410 Rock
050 0411 Crevasse
050 0412 Stream
050 0413 Braided stream
050 0414 Ditch or canal
050 0415 Aqueduct or pipeline
050 0416 Flume
050 0417 Penstock
050 0418 Siphon
050 0419 Channel
050 0420 Wash
050 0421 Lake or pond
050 0422 Reef
050 0423 Sand in open water
050 0424 Spoil area, dredged area, or dump area
050 0425 Fish ladder
050 0426 Holiday area

o Descriptive attribute codes

050 0601 Underground
050 0602 Overpassing
050 0603 Elevated
050 0604 Tunnel
050 0605 Right bank
050 0606 Left bank
050 0607 Under construction
050 0608 Salt
050 0609 Unsurveyed
050 0610 Intermittent
050 0611 Abandoned or discontinued - Code Deleted
050 0612 Submerged or sunken
050 0613 Wooded - Code Deleted
050 0614 Dry
050 0615 Mineral or hot
050 0616 Navigable - transportation - Code Deleted
050 0617 Underpassing
050 0618 Earthen construction - Code Deleted
050 0619 Interpolated elevation - Code Deleted
050 0620 Decimal fraction of 0.0 feet or meters
050 0621 Decimal fraction of 0.1 feet or meters
050 0622 Decimal fraction of 0.2 feet or meters
050 0623 Decimal fraction of 0.3 feet or meters
050 0624 Decimal fraction of 0.4 feet or meters
050 0625 Decimal fraction of 0.5 feet or meters
050 0626 Decimal fraction of 0.6 feet or meters
050 0627 Decimal fraction of 0.7 feet or meters
050 0628 Decimal fraction of 0.8 feet or meters
050 0629 Decimal fraction of 0.9 feet or meters
050 0630 Boulders
050 0631 Sand
050 0632 Gravel
050 0633 Rock (flat or reef)
050 0634 Mud
050 0635 Shell
050 0636 Coral
050 0637 Tide
050 0639 Undredged

o Parameter attribute codes

050 0000 Photorevised feature
051 ---- Water surface elevation, whole feet, 9999 or less
052 ---- Water surface elevation, whole meters
053 0--- Angle of rotation - Code Deleted
054 ---- Water surface elevation, whole feet, greater than 9999
056 ---- Water surface elevation, whole feet below datum
057 ---- Water surface elevation, whole meters below datum
055 0--- River mile mark
058 0000 Best estimate of classification or position
059 00-- Coincident feature

3.2.2 Node Attribute Codes

This code identifies the node at the uppermost origin of a single-line hydrographic feature. This code is used only at the true beginning of a watercourse, where it first appears on the map; it is not used where one hydrographic feature diverges from another, or where a particular name first appears. Do not use this code for a single-line feature that originates at a water body (see code 050 0002).

Use this code in conjunction with code 050 0300 if a single-line hydrographic feature originates at a spring.

This code identifies the node where a single-line hydrographic feature originates either within the limits of, or at the point of exit from, a water body. It is not used to identify any subsequent exits from water bodies further downstream (see code 050 0005).

When a single-line hydrographic feature is shown beginning within, rather than at, a water body, this code is applied only to the beginning point, not to the point where the feature crosses the perimeter of the water body.

This code identifies the definite point where a single-line or double-line hydrographic feature disappears. This code is used only if the sink is shown by symbols 407(A), 141.8(B), 541.12(C), or 2202.04(D), or labeled "Stream Disappears."

On a single-line feature, digitize a node at the apex of the sink symbol, where it intersects the stream, and assign the node this code. On a double-line feature, digitize a line across the end of the feature and assign the line this code.

This code identifies the node where a single-line hydrographic feature enters a water body, or ends within the limits of a water body. (This includes the node where a single-line hydrographic feature widens to a double-line hydrographic feature.)

When a single-line hydrographic feature is shown ending within, rather than at, a water body, this code is applied only to the end point, not to the point where the feature crosses the perimeter of the water body.

This code identifies the node where a single-line hydrographic feature exits a water body, or begins within the limits of a water body, other than the upper origin (see code 050 0002). (This includes the node where a double-line hydrographic feature narrows to a single-line hydrographic feature.)

When a single-line hydrographic feature is shown beginning within, rather than at, a water body, this code is applied only to the beginning point, not to the point where the feature crosses the perimeter of the water body.

3.2.3 Area Attribute Codes

This code is described in section 3.0.6.1.

This code identifies an area shown by symbols 450(A), 141.16(B), 541.28(C), or 2203.08(D). Generally labeled "Alkali flat."

The outline of the area is unattributed.

This code identifies a constructed basin as shown by symbols 179(A), 112.6(B), or 512.61(C). May be labeled.

The outline of the area is coded shoreline (050 0200) or manmade shoreline (050 0201).

Do not use this code for an artificially impounded water body with a predominantly natural shoreline (see code 050 0421). See "Feature Classification and Delineation" in section 3.2.1 for more information.

This code identifies an area shown by symbols 180(A), 512.62(C), or 2106.08(D). Generally labeled "Reservoir," but may be named.

The outline of the area is unattributed.

This code does not apply to 1:100,000-scale maps.

This code identifies an area shown by symbols 428, 429, 430 (A); 141.27, 141.28 (B); 541.43, 541.44, 541.45 (C); or 2205.04(D).

The outline of the area is unattributed.

This code identifies each section of a salt evaporator shown by symbols 439(A), 141.15(B), 541.27(C), or 2205.10(D). Must be labeled "Salt Evaporator."

The outline of the area and any internal separators are unattributed.

Inundation areas, which are lands subject to flooding, may be either controlled or uncontrolled.

Controlled inundation areas, shown by symbols 448(A), 141.38(B), or 541.56(C), have structures, such as dams or embankments, to control the water and inundate specific areas. Controlled inundation areas include debris basins, dewatering areas, percolator basins, retarding basins, and spreading grounds, as well as the area between the normal operating level and the high water line in lakes impounded by dams. If the high water line is labeled with an elevation value, the elevation parameter code is also assigned to the area. The outline of a controlled inundation area is unattributed.

Uncontrolled inundation areas include areas along the coast where flooding is natural and periodic, as shown in the description following symbol 454(A), 146.1(B), or 546.1(C). Only the low-water line of the uncontrolled inundation area is coded (see code 050 0209). The line for the approximate limit of flooding is unattributed.

This code identifies an area used for production of finfish, shellfish, or aquatic plants. These areas may be shown by a variety of treatments generally similar to that for fish hatchery, which is shown by symbols 179(A), 112.6(B), 512.61(C), or 2205.11(D). Must be labeled to indicate that it is an aquaculture site, but the label may vary depending on the species and the controlling agency. Includes fish hatchery, fish farm, minnow pond, catfish farm, crayfish farm, shrimp farm, watercress pond.

The outline of the area and any internal separators are unattributed.

Fish ponds, which are shown in the ocean on maps of Hawaii, are not collected in the DLG.

This code identifies a basin for the storage or treatment of water related to industrial use. Common labels include "Industrial Waste Pond," "Cooling Pond," "Fly Ash Pond," "Clarification Pond," "Settling Basin." If unlabeled, may still be identifiable as an industrial water impoundment because of proximity to an industrial site.

The outline of the area and any internal separators are unattributed.

This code identifies an area shown by symbols 702(A); 141.39(B); 541.57(C); 2108.02 or 2203.07 (D). This symbol is used when a dam is under construction and the limits of the intended reservoir are known. If the high water line is labeled with an elevation value, the elevation parameter code is also assigned to the area.

The outline of the area is unattributed.

All features shown within the area to be submerged are collected in the appropriate category. Any hydrographic features collected as areas within the area to be submerged are assigned this code in addition to all other appropriate codes. For example, a double-line stream within an area to be submerged is coded 050 0412 and 050 0108.

This code identifies an area related to the treatment of sewage, which may be shown by symbols 178(A); 112.5,(B); 512.59(C); or 2205.12, 2205.13 (D). Generally labeled "Sewage Disposal Pond." If unlabeled, may still be identifiable as a sewage disposal pond because of proximity to a sewage disposal plant.

The outline of the area and any internal separators are coded shoreline (050 0200) or manmade shoreline (050 0201).

This code identifies an area shown by symbols 323(A), 134.2(B), 538.1(C), or 2112.05(D). Generally labeled "Tailings Pond."

The outline of the area is unattributed.

This code identifies an area shown by symbols 431(A), 143.1(B), 543.1(C), or 2205.05(D).

Any portion of a wetland that is overprinted with blue as in symbols 433(A), 143.2(B), 543.2(C), or 2205.06(D), or is overprinted with both blue and green as in symbols 143.4(B) or 543.4(C), is also coded submerged or sunken (050 0612). The green tint indicates woods, which are collected in the Vegetative Surface Cover category.

Wetlands less than or equal to 0.10 inches in length may be shown on the graphic, but they are not collected in the DLG.

The outline of the area, which follows the edge of the pattern or open window negative, is unattributed.

This code identifies an area shown by symbols 437(A); 144.1(B); 544.1(C); or 2205.08, 2402.06 (D).

The outline of the area, which follows the edge of the pattern or open window negative, is unattributed.

This feature is no longer collected.

This code identifies an area shown by symbols 438(A), 141.36(B), 541.49(C), or 2205.09(D). Must be labeled "Cranberry Bog."

The outline of the area is unattributed. Internal separators may be shown on the map, but are not collected in the DLG.

This code identifies a number of features that fall into the general category of flat (foreshore flats, areas that uncover within or alongside reefs, and the area between the shoreline and sounding datum line on topographic-bathymetric editions). On topographic editions, these features are shown by symbols 232(A), 517.1(C), or 2113.01(D). On topographic-bathymetric editions, flats are shown by symbols 135.7(B) or 535.10(C).

Areas that uncover within or alongside reefs, which may be shown by either black sand pattern or brown tint, depending on whether the edition is topographic or topographic-bathymetric, are collected as flats. If a reef encircles an area and the closed portion of the reef symbol points outward, then the area within the reef uncovers (even though it may be shown with the blue water symbology); digitize the area within the reef and assign it the flat code. Do not add the code for the larger hydrographic feature in which the flat occurs, since the blue tint should have been cleared within the reef.

Except as just noted, any area of flat overprinted with blue tint is also assigned the code of the larger hydrographic feature in which it occurs.

If the area is labeled boulder, sand, gravel, rock, mud, shell, or coral, also add the appropriate descriptive code (see codes 050 0630 through 050 0636).

Do not apply this code to sand dunes, sand in open water (see 050 0423), or beach areas on dry land.

The outline of the area is coded shoreline (050 0200), apparent shoreline (050 0207), sounding datum line (050 0208) or reef (050 0422). If the outline of the area is not symbolized, it is unattributed.

This code identifies a seaward area of water.

Where a double-line stream enters a bay, estuary, gulf, ocean, or sea, a closure line (050 0202) is digitized to separate the stream from the seaward area of water. The line is placed where the conformation of the land and water make the division obvious, or, if no division is obvious, where the stream reaches a width of 1 nautical mile (6,080 feet) with no further constrictions.

Where a gut adjoins a bay, estuary, gulf, ocean, or sea, a closure line (050 0202) is digitized to separate the gut from the seaward area of open water.

The outline of the area is coded shoreline (050 0200), manmade shoreline (050 0201), apparent shoreline (050 0207), sounding datum (050 0208), low-water line (050 0209), or closure line (050 0202).

This code is not used for named bays on streams and lakes. Such embayments are simply collected as part of the stream or lake on which they occur.

This code identifies a shoal area shown by symbols 243(A), or 512.142(C). Generally named, but may be labeled.

When collecting from topographic editions, the outline of the area is coded limiting danger line (050 0206). When collecting from topographic-bathymetric editions, the outline of the area, which is indicated by a bathymetric contour, is collected as an unattributed line.

The shoal area is also assigned the code of the larger hydrographic feature in which it occurs.

This code does not apply to 1:100,000-scale maps.

This code identifies each section of an evaporator shown by symbols 439(A), 141.15(B), 541.27(C), or 2205.10(D). Must be labeled "Soda Evaporator."

The outline of the area and any internal separators are unattributed.

This code identifies an area shown by symbols 141.17(B), or 541.29(C). Must be labeled "Duck Pond."

The outline of the area and any internal separators are unattributed.

The area beyond the national boundary is coded as a void area to distinguish it from the background area. The outline of the void area is unattributed, unless it is defined by a symbolized feature in the Hydrography category.

This code identifies an obstruction area in a water area shown with a double dashed line as in symbols 245(A), 512.143(C), or 2113.06(D). Must be labeled "Cable Area," "Pipeline Area," "Cable-Pipeline Area," or "Pipeline Obstruction Area."

The portion of the outline of the area that is shown with the dashed symbology is unattributed, and closure lines (050 0202) are collected to close off the open end or ends. The obstruction area is also assigned the code of the larger hydrographic feature in which it occurs.

This code does not apply to 1:100,000-scale maps.

A gut is a channel that is influenced by the tide of the body of water into which it flows, and within which the direction of water flow alternates with the rise and fall of the tide. Although some portion of almost every hydrographic feature that connects to a bay, estuary, gulf, ocean, or sea technically meets this definition, this code is only used in coastal areas where the non-tidal direction of flow cannot be determined readily and confidently. These are generally fairly extensive areas of marsh, wetland, swamp, or bog (050 0111) and/or low-lying land, intersected by a network of interconnecting water bodies. Named bayous, legs, narrows, slough, slues, creeks, inlets, or passages are often indicators of tidal influence on direction of flow.

The landward extent of a gut is wherever the direction of flow can be determined readily and confidently. This is typically at or near the lowest contour. Where a double-line stream enters a gut a closure line (050 0202) is digitized to separate the stream from the gut.

The seaward extent of a gut is where open water begins. A closure line is digitized to separate the gut from the bay, estuary, gulf, ocean, or sea.

Typically a gut is collected as a single fairly extensive area; the shoreline around all of the interconnecting water bodies is collected and the entire water area is collected as a single area. The individual water bodies and channels within a gut are not closed off from one another, unless they are features distinct from the gut. For example, the pipeline canals shown on maps of gulf coast oil fields must be closed off from the surrounding gut and collected as ditch or canal (050 0414).

The outline of the area is coded shoreline (050 0200), manmade shoreline (050 0201), apparent shoreline (050 0207), sounding datum (050 0208), low-water line (050 0209), or closure line (050 0202).

A dry-dock consists of a rectangular basin, a gate, and various walls. This code identifies only the dry-dock chamber, which is collected as an area. The gate at the end of the dry-dock chamber is collected as a line using code 050 0409; this line connects the side walls and passes through the apex of the gate symbol. If the side walls are parallel to one another, this line is perpendicular to the sidewalls. However, if the side walls are not parallel to one another, this line is parallel to an imaginary line that passes through the endpoints of both legs of the gate symbol. The walls that form the chamber of the dry-dock, shown on the map with black lines, are collected as manmade shoreline (050 0201).

The dry-dock chamber is also assigned the code of the larger hydrographic feature in which it occurs.

This code identifies an area related to purification and distribution of water, which may be shown by symbols 178(A), 112.5(B), 512.59(C), or 2205.13(D). Generally labeled "Filtration Pond" or "Filtration Bed." If unlabeled, may still be identifiable as a filtration pond because of proximity to a filtration plant or waterworks.

The outline of the area and any internal separators are unattributed.

This code identifies an area shown by a treatment similar to that in symbol 240(A), where the holding qualities for an anchor are poor, or where danger exists of striking or fouling the ground or other obstructions. Must be labeled "Foul Ground" or "Foul Area."

The outline of the area, which is indicated by a bathymetric contour, is collected as an unattributed line.

The foul ground area is also assigned the code of the larger hydrographic feature in which it occurs.

This code is used only when collecting from topographic-bathymetric editions. This code does not apply to 1:100,000-scale maps.

This code identifies an area having a danger from unexploded ordnance. The symbolization is similar to that for shoal area--see symbols 243(A), or 512.142(C). Must be labeled to indicate danger from explosives.

The outline of the area, which is indicated by a bathymetric contour, is collected as an unattributed line.

The mine danger area is also assigned the code of the larger hydrographic feature in which it occurs.

This code is used only when collecting from topographic-bathymetric editions. This code does not apply to 1:100,000-scale maps.

3.2.4 Line Attribute Codes

This code identifies a natural shoreline shown by symbols 400(A), 141.1(B), 541.1(C), or 2203.01(D). This code is also used to define the shorelines of double-line streams and ditches when the direction of flow cannot be determined (when direction of flow can be determined, use codes 050 0605 and 050 0606, rather than this code).

This code identifies a constructed shoreline shown by a black line.

Although breakwaters, jetties, piers, docks, causeways, and wharfs are collected in the Manmade Features category (see code 200 0466) any portion of a single-line breakwater, jetty, pier, dock, causeway, or wharf that defines the shoreline (that is, has water on one side and land on the other) is assigned the manmade shoreline code. When a breakwater, jetty, pier, dock, causeway, or wharf is collected as an area, any portion of the outline that is symbolized as manmade shoreline is collected as manmade shoreline. Although covered piers and wharfs are collected in the Manmade Features category as buildings (general case), any portion of the perimeter of a covered pier or wharf that bounds water is collected as manmade shoreline.

This codes identifies a line segment digitized to form the closure of an areola feature whose outline is not explicitly symbolized. The most common uses of closure lines are to separate two or more areas that must be assigned different sets of attribute codes, and to separate double-line hydrographic features that flow into one another and are coded with right and left bank. For example, a closure line is used wherever a double-line stream enters a lake or pond, or a bay, estuary, gulf, ocean, or sea, or wherever a double-line stream enters another double-line stream (if either of the streams is coded with right and left bank).

Digitize a closure line across the water body from one shoreline to the other shoreline at the place where it appears that one water body flows into the next. In complex areas, where it may not be clear which of one or more branches flows into the other, it does not matter which branch is closed with the closure line; select one.

A closure line is also digitized to close off areas that have only a portion of the perimeter symbolized when the symbolized portion is collected as an unattributed line and the unsymbolized portion has not been suppressed because of symbol conflict with a higher order feature. For example, a channel is shown by dashed lines along its length; the channel ends are left unsymbolized. The portrayed dashed lines are collected as unattributed lines and the ends of the area are closed off with closure lines.

This code identifies a line shown by symbols 401, 415 (A); 141.3(B); 541.3(C); or 2203.02(D), which indicates that the shoreline cannot be definitely established. Note that on 1:24,000-scale quads compiled using older Part 6 symbology, the same symbol which is now used for indefinite shoreline was used for both indefinite shoreline and the shoreline of intermittent water bodies. Only apply this code to the outlines of areas as indicated in Appendix 3.2.A, and do not apply this code to the outline of intermittent or dry water bodies.

This code is no longer used.

This code identifies the outline of a Carolina bay as shown by symbols 401(A), 141.7(B), 541.17(C), or 2205.19(D).

A Carolina bay is always collected as a line, even if the outline forms a closed ellipse, so the interior area is not assigned an attribute code unless it is a hydrographic feature in its own right. Because a Carolina bay is not collected as an area the codes for upper origin at water body (050 0002), entering water body (050 0004), and exiting water body (050 0005) are not used in conjunction with this feature.

This code identifies a line which represents the limit of an area considered to be dangerous for navigation. An example is shown by symbol 244(A). This code is used only when collecting from topographic editions; on topographic-bathymetric editions bathymetric contours indicate the extent of areas dangerous for navigation.

Only limiting danger lines related to rocks (050 0410), shoals (050 0117), and wreckage (which is collected in the Manmade Features category using codes 200 0467 and 200 0468) are collected. See the individual coding description for instructions on collecting the feature within the limiting danger line.

The area within a limiting danger line is also assigned the code of the larger hydrographic feature in which it occurs.

This code identifies a line shown by symbols 141.2(B) or 541.2(C), which represents a coastal shoreline in areas of marsh, grass, mangrove, or other similar marine vegetation. This symbol is shown at the outer edge of vegetation, instead of the mean high-water line.

This code is used only when collecting from topographic-bathymetric editions.

This code identifies a line shown by symbols 141.40(B) and 541.59(C), which represents the starting elevation (0) for bathymetric contours and is the mean lower low-water line.

This code is used only when collecting from topographic-bathymetric editions.

This code identifies a line shown by symbol 546.1(C), which represents the mean low-water or mean lower low-water line. The low-water line is shown as the lower limit of uncontrolled inundation areas in flat coastal areas where natural and periodic flooding occurs and the high water line cannot be located.

This codes identifies a line shown by symbols 141.9(B) and 541.16(C). Generally named, but may be labeled "Airboat Trail."

Canoe trails or wilderness waterways, also shown by these symbols, are not collected in the DLG.

This code is described in section 3.0.6.3.

3.2.5 Single-Point Attribute Codes

This code identifies a spring shown by symbols 427(A), 141.25(B), 541.40(C), or 2205.03(D). Must be labeled "Spring."

The spring is digitized at the center of the circular part of the symbol, and the tail is ignored. Unless the center of the circle falls directly on a line collected in this category, the spring is collected as a degenerate line. When the spring falls directly on a stream it is collected as a node, and the general alignment of the stream, rather than the tail symbol, is followed when digitizing the stream. Use this code in conjunction with code 050 0001 if the spring is the upper origin of the stream.

This code identifies a well shown by symbols 426(A), 141.26(B), 541.39(C), or 2205.02(D). Must be labeled "Well."

This code identifies a well shown by symbols 426(A), 141.26(B), 541.39(C), or 2205.02(D). Must be labeled "Flowing Well" or "Artesian Well."

A riser is a vertical overflow pipe controlling the water level in a reservoir, and is shown by symbols 198(A), 112.1(B), 512.72(C), or 2111.03(D). Must be labeled "Riser."

This code identifies a special type of spring that ejects hot water or steam periodically, shown by symbols 426, 427(A), 141.25, 141.26 (B), 541.39, 541.40 (C), or 2205.02, 2205.03 (D). Must be labeled "Geyser," "Gas Vent," "Mud Pot," "Fumarole," or "Steam Vent."

This code identifies a windmill shown by symbols 199(A), 112.3(B), 512.69(C), or 2111.04(D). If the label indicates the well is dry or salt, also assign code 050 0608 or 050 0614.

The windmill is digitized at the point where the arms of the symbol cross, or on older symbology, at the center of the circle.

This feature is no longer collected.

3.2.6 General Purpose Attribute Codes

This code identifies a rapids shown by symbols 442, 443 (A); 141.31, 141.32 (B); 541.53, 541.54 (C); or 2205.16, 2205.17 (D). Generally labeled "Rapids," but may be named.

On a single-line stream, if the upstream and downstream tick are less than 0.02 inch apart, collect the rapids as a node equidistant between the ticks. If the upstream and downstream tick are 0.02 inch or more apart, or if several ticks (often irregularly spaced) are shown, the rapids is collected as a line, by assigning the section of stream between the ticks this code in addition to the stream code (050 0412). Use your best judgement in determining whether to collect a particular section of stream as a single long rapids or a series of short rapids. Factors to consider include the distance between ticks, and the placement of the "Rapids" label.

On a double-line stream, a rapids is always collected as an area. If the rapids extends completely across the stream, unattributed lines are digitized from bank to bank along the upstream and downstream edges of the rapids. If the rapids does not extend completely across the stream, an unattributed line is digitized along the extent of the rapids. The banks of the stream are collected as right and left bank, shoreline, manmade shoreline, or indefinite shoreline, as appropriate. The rapids area is also assigned the stream code (050 0412).

This code identifies a falls shown by symbols 440, 441 (A); 141.29, 141.30 (B); 541.51, 541.52 (C); or 2205.14, 2205.15 (D). Generally labeled "Falls," but may be named.

On a single-line stream, a falls is collected as a node. On a double-line stream, a falls is collected as a line that extends from one shoreline to another. If the falls is symbolized by a pattern of ticks parallel to the shore, as in symbols 440(A), 141.29(B), 541.51(C), or 2205.14(D), the line is digitized along the upstream edge of the pattern of ticks.

A gravel pit or quarry filled with water is collected as a lake or pond (050 0421). This code is no longer used.

This code identifies a gagging station, shown by symbols 200(A), 112.45(B), 512.113(C), or 2111.05(D).

If the center of the symbol falls directly on a line collected in this category, the gagging station is collected as a node. Otherwise, the gagging station is collected as a degenerate line.

If the gagging station is labeled "Tide Gage" or "Tidal Gage," also apply code 050 0637.

A pumping station may be shown as an individual building, or a group of structures. Must be named or labeled to indicate it is a pumping station.

Use this code only for pumping stations associated with water (canals or ditches). Pumping stations associated with oil or gas are collected in the Pipelines, Transmission Lines, and Miscellaneous Transportation Features category.

A pumping station is collected as a degenerate line if the area occupied by the individual building or group of structures is less than 120 feet in the shortest dimension. If the area occupied is 120 feet or more in the shortest dimension, it is collected as an area. When collected as an area, the outline of the area is unattributed. Individual buildings within the area are collected as general case buildings (200 0400) in the Manmade Features category.

Do not collect individual pumps shown with a circle or a located object symbol.

This code identifies a water intake shown by a variety of treatments. It may be shown by the located object symbol, 198(A), 512.72(C), or 2111.03(D), or by a small outlined perimeter, either at the end of a pipeline, or by itself in open water. The intake itself, or the pipeline, may be labeled "Water Intake," "Waterworks Intake," or "Intake." The actual intake at the end of the pipeline may not be symbolized at all. Regardless of how it is shown, collect the intake as a degenerate line in open water, or as a node at the end of the pipeline. The pipeline itself is collected using code 050 0415.

This code does not apply to 1:100,000-scale maps.

This code identifies a feature shown by symbols 152, 153, 155 (A); 112.63, 112.65 (B); 511.20, 512.35, 512.37 (C); or 2108.01, 2108.02, 2108.04 (D). Generally labeled "Dam," "Weir," or "Diversion Weir," but may be named.

When shown as a single-line, the feature is collected as a line, and assigned this code. If the feature is carrying a road, as in symbols 155(A); 112.65(B); 511.20, 512.37 (C); or 2108.04(D), digitize it as the centerline equidistant between the two road casings.

When shown to scale, the feature is collected as an area. The portion of the outline of the area that bounds water is coded manmade shoreline (050 0201), and the remainder of the outline is unattributed.

The radiating lines within symbol 153(A) are not digitized.

When an earthen dam is shown by symbol 132.14(B), digitize a line along the dam and assign it the shoreline (050 0200) code. Dams of earthen construction shown by contours are collected only in the Hypsography category (except during limited update digital revision).

A lock consists of a rectangular basin, gates, and various walls. This code identifies only the lock chamber. The gates at either end of the lock chamber are collected as gate (050 0409). The walls that form the chamber and any other wall-like structures associated with the lock, and shown on the map with black lines, are collected as manmade shoreline (050 0201).

If a single gate is shown on a single-line stream and labeled "Lock," the gate symbol represents both the lock chamber and its gates. Digitize a node and assign it this code.

If two gates (indicating the gates at both ends of the lock) are shown on a single-line stream and labeled "Lock," collect each gate as a node using code 050 0409 and collect the line between the gates, which is the lock chamber, using this code in addition to the stream code (050 0412).

If the lock is shown to scale, digitize the lock as an area that is bounded by the gates on each end and by the walls that enclose the chamber. Use this code only on the area. Digitize each gate as a line using code 050 0409; this line connects the side walls and passes through the apex of the gate symbol. If the side walls are parallel to one another, this line is perpendicular to the side walls. However, if the side walls are not parallel to one another, this line is parallel to an imaginary line that passes through the endpoints of both legs of the gate symbol. Digitize the walls and other associated structures using code 050 0201 (manmade shoreline).

If the lock is shown to scale, but the lock is shown only by gates across a double-line stream (there are no symbolized sidewalls), digitize the lock as an area that is bounded by the gates on each end and by the shorelines of the stream. Use this code only on the area. Digitize each gate as a line using code 050 0409; this line connects the side walls and passes through the apex of the gate symbol. If the side walls are parallel to one another, this line is perpendicular to the side walls. However, if the side walls are not parallel to one another, this line is parallel to an imaginary line that passes through the endpoints of both legs of the gate symbol. Digitize the shorelines using codes 050 0605 and 050 0606.

When collected as an area, the lock chamber is also assigned the code of the larger hydrographic feature in which it occurs.

This code identifies a constructed passage for surplus water to run over or around a dam. Since a spillway may be shown by a variety of treatments and is not always labeled, considerable judgement may be involved in identifying and collecting this feature.

If shown by a small circle or dot, the feature is collected as a degenerate line. If shown by either a perennial or intermittent single-line hydrographic feature, it is collected as a line. If shown by a black outline, collect the feature as an area; any portion of the outline of the area that forms the shoreline of an adjacent water body is collected as manmade shoreline (050 0201), and the remainder of the outline of the area is unattributed. If shown as an integral part of the dam, collect the feature as a node on the digitized line of the dam.

If a spillway elevation is shown, add parameter code 05N ---- , which is used to encode the water surface elevation, to the node, point, line, or area.

If the label "Spillway Elevation NNNN," placed within the impounded water body, is the only indication that a spillway exists, do not collect a spillway; add the spillway elevation value to the impounded water body area instead. If another elevation value is shown for the impounded water body, do not collect the spillway elevation value.

A spillway shown by contours is collected only as contour in the Hypsography category, even if labeled. If a spillway elevation is shown, collect it as described in the preceding paragraph.

This code identifies a variety of gates used to control or divert the flow of water. Common labels include "Lock," "Sluice," "Dry-dock," "Flood," "Tidal," "Head," or "Check."

If shown by a > pointing upstream on a single-line hydrographic feature collect as a node at the apex of the symbol, unless it is labeled "Lock." See code 050 0407 for collection of a lock chamber symbolized by a single gate. If shown by a straight tick or black line on a single-line hydrographic feature collect as a node where the tick or line crosses the feature.

If shown by a > pointing upstream on a double-line hydrographic feature collect as a degenerate line at the apex of the symbol, unless it is a dry-dock gate or lock gate. If shown by a straight tick or black line on a double-line hydrographic feature, the entire extent of the tick or line is digitized and assigned this code.

A dry-dock gate or lock gate shown by a > on a areola hydrographic feature is collected as a line that connects the side walls of the dry-dock or lock on either side of the gate, and passes through the apex of the gate symbol. If the side walls are parallel to one another, this line is perpendicular to the side walls. However, if the side walls are not parallel to one another, this line is parallel to an imaginary line that passes through the endpoints of both legs of the gate symbol.

This code identifies a rock shown by symbols 236, 237, 246 (A); 112.97, 112.99 (B); 512.136, 512.137, 512.158, 512.159, 512.160(C); or 2113.03(D), or an individual rock within a group of rocks shown by symbols 238(A); 112.98(B); 512.138, 512.159 (C); or 2113.04(D). Each rock is digitized as a degenerate line.

A sunken rock shown by symbols 246(A), 112.99(B), or 512.160(C) is also assigned descriptive code 050 0612.

If a dotted line is shown around a rock or rocks, as in symbols 236, 238 (A); old symbol 112.98(B); 512.136, 512.138 (C); or 2113.04(D), the line is collected as a limiting danger line (050 0206).

This code identifies a crevasse shown by symbol 453(A).

If a crevasse field contains three or fewer crevasses, each individual crevasse is collected as a line. If a crevasse field contains four or more lines it is collected as an area. The outline of the field is unattributed.

This code does not apply to 1:100,000-scale maps.

This code identifies all naturally flowing water. Streams are shown by symbols 402 through 406, 408 (A); 141.4 through 141.6 (B); 541.4 through 541.9 (C); or 2202.01 through 2202.03, 2202.05 (D). See "Feature Classification and Delineation" in section 3.2.1 for guidance in distinguishing between a stream and a ditch or canal.

If shown as perennial, as in symbols 402, 403 (A), 141.4(B), 541.4, 541.5 (C), or 2202.01(D), this code is used alone. Any stream shown by these symbols is collected as a perennial stream, even if named or labeled as a wash.

If shown as intermittent, as in symbols 405, 406 (A), 141.6(B), 541.7, 541.8 (C), or 2202.02(D), add the descriptive code for intermittent (050 0610). Any stream shown by these symbols is collected as an intermittent stream, even if named or labeled as a wash.

If shown as unsurveyed, as in symbols 408(A), 141.5(B), 541.10, 541.11 (C), or 2202.05(D), add the descriptive code for unsurveyed (050 0609).

When a stream is collected as an area, the outline of the area is coded right bank (050 0605) and left bank (050 0606), shoreline (050 0200), manmade shoreline (050 0201), indefinite shoreline (050 0203), closure line (050 0202). (See section 3.2.1.3 on Line Attribute Codes for more information.)

A submerged stream within an impounded water body, shown by dashed blue lines, is digitized as a separate area and assigned this code and the descriptive code for submerged or sunken (code 050 0612). The outline of the area is unattributed, except for the open ends, which are collected as closure lines (050 0202).

This code identifies a braided stream, which is shown by a treatment generally similar to that in symbols 404(A), 541.6, 541.9 (C), or 2203.03(D).

Although a braided stream is typically perennial in nature, at its prevailing stage it does not entirely cover its bed. Instead, it flows in a number of sub- channels that expose island-like sand or gravel bars. The course of these sub-channels changes frequently.

This code is only used when the braiding involves at least five sub-channels, or covers an extensive area at least one-quarter mile in width and one mile in length.

The braided stream is collected as an area. The limit of the area on either side is the far bank of the outermost channel, or the limit of the sand or gravel stream bed, whichever extends furthest. These limiting lines are coded as right bank (050 0605) and left bank (050 0606). The upstream and downstream extent of the area is the point where the stream is unbraided, or insufficiently braided. The braided area is separated from a double-line stream using closure lines (050 0202). If the braided area occurs on a single-line stream, the nodes where the stream enters and exits the braided area are coded 050 0004 and 050 0005, respectively.

No streams (either single-line or double-line, intermittent or perennial) are collected within the braided area. The sand or gravel is collected in the Non-Vegetative Features category.

The descriptive code for intermittent (050 0610) is never used in conjunction with this code, regardless of how the braided stream is symbolized on the map.

This code identifies any manmade, flowing water feature used for irrigation, drainage, or transportation shown by symbols 416 through 422 (A); 141.19, 141.20 (B); 541.31, 541.32 (C); or 2204.01 through 2204.06 (D). See "Feature Classification and Delineation" in section 3.2.1 for guidance in distinguishing between a stream and a ditch or canal.

The descriptive code for intermittent (050 0610) is never used in conjunction with this code, regardless of how the ditch or canal is symbolized on the map.

The only descriptive attribute codes used in conjunction with ditch or canal are underpassing (050 0617), overpassing (050 0602), and tunnel (050 0604).

When a ditch or canal is collected as an area, the outline of the area is coded right bank (050 0605) and left bank (050 0606), shoreline (050 0200), manmade shoreline (050 0201), indefinite shoreline (050 0203), closure line (050 0202). (See section 3.2.1.3 on Line Attribute Codes for more information.)

If a canal is labeled "Pipeline Canal," the canal is collected using this code. The pipeline, which carries oil, is collected in the Pipelines, Transmission Lines, and Miscellaneous Features category.

This code identifies features represented by symbols 416, 418, 419, 421, 423, 424, 425 (A); 141.19 through 141.23 (B); 541.31 through 541.36 (C); or 2204.01, 2204.03, 2204.04, 2204.06 through 2204.09 (D). Generally must be labeled "Aqueduct" or "Pipeline," but some pipelines associated with water intakes may be labeled "Water Intake," "Waterworks Intake," or "Intake." (See code 050 0405 for coding of the intake itself, which is collected even if only the pipeline is symbolized on the map.)

An aqueduct in a tunnel is shown by symbols 424(A), 141.23(B), 541.35(C), or 2204.08(D) regardless of size. The portion of the aqueduct that is in the tunnel is digitized as a line and assigned this code and the code for tunnel (050 0604). A feature shown by symbol 424(A) and labeled "Water Tunnel" is coded the same way.

The only other descriptive attribute codes used in conjunction with aqueduct or pipeline are underground (050 0601), overpassing (050 0602), elevated (050 0603), submerged or sunken (050 0612), and underpassing (050 0617).

Pipelines which carry gas or oil, shown in black on the map, are collected in the Pipelines, Transmission Lines, and Miscellaneous Transportation Features category.

If a canal is labeled "Pipeline Canal," it is collected as a ditch or canal (050 0414). The pipeline is collected in the Pipelines, Transmission Lines, and Miscellaneous Features category.

This code identifies a feature shown by symbols 416, 418, 419, 421, 423, 425 (A); 141.19, 141.21, 141.22 (B); 541.31 through 541.34, 541.36 (C); or 2204.01, 2204.03, 2204.04, 2204.06, 2204.07, 2204.09 (D). Must be labeled "Flume." A flume is an open, inclined, artificial channel.

No descriptive attribute codes are used in conjunction with flume.

This code identifies a feature shown by symbols 423, 425 (A); 141.21(B); 541.34, 541.36 (C); or 2204.07, 2204.09 (D). Generally labeled "Penstock." If unlabeled, may still be identifiable based on context; a penstock is pipe conveying water from a canal or a dam into the turbine of a hydroelectric generating plant.

If a pipe that conveys water into the turbine of a hydroelectric generating plant is shown by symbols 424(A), 141.23(B), or 2204.08(D), collect it as an aqueduct or pipeline (050 0415) in a tunnel (050 0604), rather than a penstock.

This code identifies a feature shown by symbols 452(A), 141.21(B), 541.41(C), or 2205.18(D). Must be labeled "Siphon."

No descriptive attribute codes are used in conjunction with siphon.

This code identifies a dredged channel shown by symbols 444(A); 112.94, 141.34 (B); or 512.154 through 512.156, 541.15 C), or a named undredged channel shown by periodic labeling.

A dredged channel shown by parallel dashed lines is collected as an area. The symbolized portion of the outline of the area is unattributed. A closure line (050 0202) is digitized to close off any unsymbolized portion of the outline.

Any portion of a named waterway (generally the Intracoastal Waterway) that is undredged, and therefore shown only by periodic labeling, is collected as a line and assigned both this code and the undredged descriptive code (050 0639). The line is digitized following the course of the waterway and passing through the center line of the periodic occurrences of the label.

On topographic editions, a channel area is shown with blue tint, and is therefore, also assigned the code of the larger hydrographic feature in which it occurs. On topographic-bathymetric editions, a channel area is cleared of tint, and therefore, is not assigned the code of the larger hydrographic feature in which it occurs.

This code does not apply to the course of a submerged river in an impounded water body (see code 050 0412).

This code identifies a wash, which is a portion of a stream bed that is usually dry and contains water only during or after a rainstorm or snowmelt.

A single-line wash shown by an irregular dotted brown line (similar to a stipple pattern) is normally collected as a line. However, where a single-line wash is shown as a channel through an areola wash it is not collected in the DLG. Any feature shown by symbols 409(A), 141.6(B), 541.13(C), or 2202.06(D) is collected as an intermittent stream, even if named or labeled as a wash.

An areola wash is shown by brown sand pattern, as in symbols 317(A), 134.1(B), 534.3(C), or 2112.04(D). The outline of the area is unattributed.

Since a wash is never perennial, any feature named or labeled as a wash, but symbolized as perennial, is collected as a stream (050 0412) rather than a wash. If any perennial streams, or several interlacing intermittent streams, are shown running through an area of brown sand pattern, the area may be a braided stream (see code 050 0413), or it may be an area of sand adjacent to a stream (such sand is collected in the Non-Vegetative Features category).

This code identifies a standing body of water with a predominantly natural shoreline. Lakes or ponds are shown by symbols 410, 411, 412, 414 (A); 141.12, 141.13, 141.14 (B); 541.23, 541.25, 541.26 (C); or 2203.03, 2203.04, 2203.05, 2203.06 (D). An artificially impounded water body with a predominantly natural shoreline is collected as a lake or pond, even if named or labeled as a reservoir or river. See "Feature Classification and Delineation" in section 3.2.1 for more information.

If shown as perennial, as in symbols 410(A), 141.12(B), 541.23(C), or 2203.03(D), this code is used alone.

If shown as perennial salt, as in symbols 411(A), 141.12(B), 541.23(C), or 2203.04(D), add the descriptive code for salt (050 0608).

If shown as intermittent, as in symbols 412(A), 141.13(B), 541.26(C), or 2203.05(D), add the descriptive code for intermittent (050 0610).

If shown as dry, as in symbols 414(A), 141.14(B), 541.25(C), or 2203.06(D), add the descriptive code for dry (050 0614).

When a lake or pond is collected as an area, the outline of the area is coded shoreline (050 0200), manmade shoreline (050 0201), or indefinite shoreline (050 0203).

This code identifies a reef shown by symbols 233, 234 (A); 135.8, 112.100 (B); 512.135, 512.161, 517.2, 517.3, 535.11 (C); or 2113.02(D). Except when collected as a degenerate line, a reef is collected as a line that connects the high points of the closed, outer portion of the reef symbol. The appropriate descriptive code is also added to the line to indicate whether the reef is rock (050 0633) or coral (050 0636).

Areas that uncover within or alongside reefs, which may be shown by either black sand pattern or brown tint, depending on whether the edition is topographic or topographic-bathymetric, are collected as flats (050 0115). In addition, if a reef encircles an area and the closed portion of the reef symbol points outward, then the area within the reef uncovers (even though it may be shown with the blue water symbology) and it is collected as flat. Do not add the code for the larger hydrographic feature in which the flat occurs, because the blue tint should have been cleared within the reef.

If a reef encircles an area and the closed portion of the reef symbol points inward, then the area within the reef shown with the blue water symbology is a reef pool and is assigned the code for the larger hydrographic feature in which the reef occurs.

The code identifies an area of sand in other than tidal waters, shown by symbols 322(A), 134.3(B), 534.4(C), or 2112.03(D).

Where collected as an area, the outline of the area is unattributed.

This code identifies a feature shown by symbols 112.95(B) or 512.157(C), or by a dashed blue line. Must be labeled "Spoil Area," "Dredged Area," "Dump Area," or "Dump Site Area."

Where shown by a single dashed blue line that does not form a closed area, it is collected as a line. When shown by a single dashed blue line that does form a closed area, or by parallel dashed black lines, it is collected as an area.

Where collected as an area, the symbolized portion of the outline of the area is unattributed. A closure line (050 0202) is digitized to close off any unsymbolized portion of the outline of the area.

Because a spoil area, dredged area, or dump area is cleared of blue tint, the area is not assigned the code of the larger hydrographic feature in which it occurs.

This code is used only when collecting from topographic-bathymetric editions.

This code describes a feature shown by symbol 512.39(C) or as a labeled section of a stream. Must be labeled "Fish Ladder."

When shown by symbol 512.39(C), the feature is collected as an area. The outline of the area is coded shoreline (050 0200) or manmade shoreline (050 0201). The area is not assigned the code of the larger hydrographic feature, because the fish ladder is not actually part of the feature. The channels connecting the fish ladder to the stream are collected as ditch or canal (050 0414).

If shown as a labeled section of a single-line stream, this feature is collected as a line. Unattributed nodes are digitized at the upstream and downstream limits of the ladder, and the segment of the stream between the nodes is assigned this code in addition to the stream code.

If shown as a labeled section of a double-line stream, this feature is collected as an area. The upstream and downstream limits of the ladder are digitized as unattributed lines, and the section of the stream between those lines is assigned this code. The banks of the stream are coded as right bank (050 0605) and left bank (050 0606). The area is also assigned the code of the larger hydrographic feature on which it occurs.

This code identifies an area of inadequate or nonexistent survey data, shown by symbols 112.93(B) or 512.153(C). Must be labeled "Holiday Area" or "No

The symbolized portion of the outline of the area is unattributed. A closure line (050 0202) is collected to close off any unsymbolized portion of the outline of the area.

Because a holiday area is cleared of blue tint, it is not assigned the code of the larger hydrographic feature in which it occurs.

This code is used only when collecting from topographic-bathymetric editions.

3.2.7 Descriptive Attribute Codes

This code describes a feature labeled "Underground," or an underground aqueduct or pipeline (050 0415) shown by symbols 423(A), 141.21(B), 541.34(C), or 2204.07(D).

This code describes the portion of a feature that passes over rather than intersects another feature, as indicated by wing ticks as in symbols 425(A), 141.22(B), 541.36(C) or 2204.09(D). This code is used only where wing ticks are present, and the code is applied only to the portion of the hydrographic feature between the wing ticks. Wherever wing ticks are present, this code rather than the elevated code (050 0603) is used, even if the feature is labeled as elevated.

This code describes a ditch or canal (050 0414) or aqueduct or pipeline (050 0415) labeled "Elevated." If the portion of the feature labeled elevated is also indicated by wing ticks, as in symbols 425(A), 141.22(B), 541.36(C) or 2204.09(D), then use the overpassing code (050 0602) rather than this code.

This code describes the portion of a feature that is carried through a tunnel, shown by symbols 424(A), 141.23(B), 541.35(C), or 2204.08(D), or by the label "Tunnel." Since a tunnel is by definition underground or underpassing, codes 050 0601 or 050 0617 are not added to the portion of a feature coded tunnel.

This code describes the limit of a double-line feature on the right side when facing downstream. It is used instead of shoreline code (050 0200).

This code describes the limit of a double-line feature on the left side when facing downstream. It is used instead of shoreline code (050 0200).

This code describes a canal (050 0414) or dam (050 0406) labeled to indicate that it was under construction at the time the map was made.

This code describes any feature that is labeled "Salt."

This code describes an unsurveyed stream shown by symbols 408(A); 141.5(B); 541.10, 541.11 (C); or 2202.05(D).

This code describes any hydrographic feature that is shown as intermittent, as in symbols 405, 412 (A); 141.6, 141.13 (B); 541.7, 541.11, 541.26 (C); or 2202.02, 2203.05 (D). This code overrides the assumed default value of perennial.

This code is not added to a ditch or canal (050 0414), or a braided stream (050 0413), regardless of how they are symbolized on the map.

This code is no longer used. If a hydrographic feature is portrayed on the map as abandoned or discontinued, it is collected using all appropriate codes, but not specifically identified as abandoned or discontinued.

This code describes any feature labeled "Submerged" or "Sunken," or overprinted by blue tint to indicate that it is submerged, such as a marsh, or an old river course in an impounded water area. The outline of a submerged river course is digitized as an unattributed line.

This code is not applied to channels (050 0419).

Woods are collected only in the Vegetative Surface Cover category. This code is no longer used.

This code describes any feature labeled "Dry," or symbolized as dry, such as a dry lake, shown by symbols 134.7(B) or 534.5(C).

This code describes any well, spring, or water source that is labeled to indicate the water is hot or contains minerals. Includes mineral, hot, sulfur, alkali.

This code is no longer used. See channel (050 0419).

This code describes a feature or a section of a feature that passes underneath, rather than intersects, another feature. This code is used only when the symbol for the underpassing feature has been broken back from the overpassing feature to indicate that it is underpassing. This code is generally applied to a linear feature, such as an aqueduct under a canal. The underpassing segment is also assigned the code or codes of the hydrographic feature on which it occurs.

This code is no longer used, except during limited update digital revision. Dams of earthen construction shown by contours are collected only in the Hypsography category.

This code is no longer used. Only water surface elevations that are printed on the map are collected.

Descriptive attribute codes 050 0620 through 050 0629 are used to represent decimal fractions of feet or meters. They are used only in conjunction with the water surface elevation or river mile mark parameter attribute codes when the elevations or river mile marks are expressed to decimal fractions. It is not necessary to distinguish between feet and meters, because the unit of measurement is encoded in the associated parameter code. The specific decimal fraction values associated with each code are listed below.

050 0620 Decimal fraction of 0.0 feet or meters
050 0621 Decimal fraction of 0.1 feet or meters
050 0622 Decimal fraction of 0.2 feet or meters
050 0623 Decimal fraction of 0.3 feet or meters
050 0624 Decimal fraction of 0.4 feet or meters
050 0625 Decimal fraction of 0.5 feet or meters
050 0626 Decimal fraction of 0.6 feet or meters
050 0627 Decimal fraction of 0.7 feet or meters
050 0628 Decimal fraction of 0.8 feet or meters
050 0629 Decimal fraction of 0.9 feet or meters
050 0630 Boulders

This code describes a flat (050 0115) labeled "Boulders."

This code describes a flat (050 0115) labeled "Sand."

Do not apply this code to sand in open water (see code 050 0423).

This code identifies a flat (050 0115) labeled "Gravel."

This code identifies a flat (050 0115) or a reef (050 0422) labeled "Rock."

Do not apply this code to individual rocks or groups of rocks (see code 050 0410).

This code identifies a flat (050 0115) labeled "Mud."

This code identifies a flat (050 0115) labeled "Shell."

This code identifies a flat (050 0115) or a reef (050 0422) labeled "Coral."

This code describes a gagging station that is labeled "Tide Gage" or "Tidal Gage."

This code describes a channel that is undredged. It is used only in conjunction with code 050 0419.

3.2.8 Parameter Attribute Codes

This code is described section 3.0.6.4.

This code is added to any feature collected as a node, line, point, or area that is shown in purple on the graphic. If a feature is shown with purple tint or pattern, this code is added to the area point. If the line that bounds an area is shown in purple, this code is added to the line, even if the line would otherwise be unattributed. This code is not added to closure lines (050 0202), since these lines do not appear on the map and therefore are never shown in purple.

An unattributed line is used to separate the photorevised portion of a water body from the non-photorevised portion.

If a photorevised water body completely encloses the original water body shown in blue (that is, the entire shoreline is shown in purple) the original water body is not distinguished from the photorevised portion in the DLG; the entire water body is collected as photorevised.

This parameter is used to encode water surface elevations printed on the map. The value may be shown as "Normal Pool Elevation XXXX," "Elevation XXXX," or simply as a value printed in blue or black. This code is also used to encode a maximum potential water surface elevation shown on the line defining the limits of an area subject to controlled inundation.

Enter a value in place of the "N" in the major code as follows: 1 = whole feet, 9999 or less

2 = whole meters
4 = whole feet, greater than 9999
6 = whole feet below datum
7 = whole meters below datum

The elevation value is then entered into the minor code, flush right. If a value in feet exceeds 9999, only the final four digits are encoded in the minor code. To express elevations in decimal feet or meters, use this parameter code in conjunction with descriptive attribute codes 050 0620 through 050 0629.

Examples: 421 feet is coded as 051 0421
10014 feet is coded as 054 0014
101.5 meters is coded as 052 0101,050 0625
-3 meters is coded as 057 0003

This code is no longer used.

This parameter code is used both to identify a river mile mark, as shown by symbol 512.109(C), and to encode the mile value. A mile value is encoded for each symbolized mile mark, although on the map the mile value may be printed only at intervals, such as every fifth mark.

The mile mark is digitized at the center of the cross symbol. If the cross occurs directly on a line that is digitized in the Hydrography category, the mile mark is digitized as a node on that line. Otherwise the mile mark is digitized as a degenerate line.

Enter the mile value in the minor code flush right. If the river mile mark is expressed to a decimal fraction, use this code for the nondecimal value and code 050 0620 through 050 0629 for the decimal value.

This code is no longer used.

This code is no longer used.

For additional information regarding this Web page, contact Chris Lett, in the Division of Information Resources and Technology Management, at Chris_Lett@fws.gov

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Last Modified January 03, 2001 10:34 AM