Attribute description	Item name	Item	Item type	Domain	Item precision
Feature class (hydrography)	FClass	Integer	Short	FClass	4
Feature class (elevation)	EClass	Integer	Short	EClass	4
Feature code	FCode	Integer	Long	FCode	5
Description	Desc	Text	Text	--	250
Elevation source data	Source	Text	Text	--	128
Hydrography delineation method	Method	Text	Text	--	250
User-defined code	UserCode	Text	Text	--	25
Free-text space for user comments	Comments	Text	Text	--	250
User-defined code	UniqueID	Text	Text	--	50
Digital Elevation Model (DEM) Limitation	Limitation	Integer	Short	Limitation	1
Flow Direction Determination	FlowClass	Integer	Short	FlowClass	1

Table 3. Attribute table structure for area and point hydrographic features.

Attribute description	Item name	Item	Item type	Domain	Item precision
Feature class (hydrography)	FClass	Integer	Short	FClass	4
Feature class (elevation)	EClass	Integer	Short	EClass	4
Feature code	FCode	Integer	Long	FCode	5
Description	Desc	Text	Text	--	250
Elevation source data	Source	Text	Text	--	128
Hydrography delineation method	Method	Text	Text	--	250
User-defined code	UserCode	Text	Text	--	25
Free-text space for user comments	Comments	Text	Text	--	250
User-defined code	UniqueID	Text	Text	--	50
Digital Elevation Model (DEM) Limitation	Limitation	Integer	Short	Limitation	1

Table 4. Domain values for FlowClass feature attributes.

Domain value	Feature attributes
0	Flow direction is unable to be determined from elevation surface. Do not use for hydro-enforcement (EClass = 0)
1*	Flow direction is in digitized direction, and z-values on vertices flow downslope.
2	Flow direction is in digitized direction, and z-values on vertices flow upslope. Do not use for hydro-enforcement (EClass = 0)

*This is the default value.

Table 5. Domain values for Limitation feature attributes.

Domain value	Feature attributes
0*	No elevation dataset limitation.
1	Elevation dataset limitation.

*This is the default value.

Table 6. FCode domain values and descriptions.

FCode	Desc
0	User-defined feature
33400	Connector
33401	Connector: Culvert
33404	Connector: Indefinite Surface
33405	Connector: Terrain Breach
33410	Connector: Non-NHD Dataset
33600	Canal/ditch
34300	Dam/weir
36100	Playa
37800	Ice mass
39000	Lake/pond
42002	Underground Conduit
42800	Pipeline
44500	Sea/ocean
45000	Sink
46000	Stream/river
46800	Drainageway
55800	Artificial path

Table 7. Domain values for FClass feature attributes.

Domain value	Feature attributes
1	Hydrography feature defined within the collection criteria of the elevation-derived hydrography specifications.
2	Hydrography feature captured outside the collection criteria of the elevation-derived hydrography specifications.
9	Nonhydrography feature.

Table 8. Domain values for EClass feature attributes.

Domain value	Feature attributes
0	Not used for elevation derivative.
11	Polygon created from breakline—Polygon derived from the breaklines used for hydroflattening the elevation surface (3D polygon).
12	Polygon created from hydroflattened surface—Polygon corresponding to a hydroflattened surface, but breakline is either not available or not horizontally or vertically aligned appropriately with the DEM surface. For use in Alaska or where breaklines do not meet cartographic or horizontal requirements.
13	Polygon created without using elevation hydroflattening breakline and the surface of the waterbody is not hydroflattened in the source DEM.
2*	Linear hydrographic features that follow the elevation surface.
3	Linear features below ground level—Examples include connectors through dams, culvert connectors, and terrain breach connectors. Used for hydro-enforcement.

*This is the default value.

Table 9. Feature type description, associated geometry, and use classification.

Desc	FCode	Geometry type	FClass Domain value	EClass Domain value
Artificial path	55800	3D line, polylineZ (creates network connectivity)	1	2
Canal/ditch	33600	3D line, polylineZ (does not connect primary network features)	2	0
Canal/ditch	33600	3D line, polylineZ (creates network connectivity)	1	2
Canal/ditch	33600	3D polygon, polygonZ (polygon matches hydroflattening breaklines, breakline used)	1	11
Canal/ditch	33600	3D polygon, polygonZ (polygon based on hydroflattening surface, breakline edits required)	1	12
Canal/ditch	33600	3D polygon, polygonZ (no hydroflattening breakline available, polygon newly captured)	1	13
Connector	33400	3D line, polylineZ	1	3
Connector: Culvert	33401	3D line, polylineZ	1	3
Connector: Indefinite surface	33404	3D line, polylineZ (creates network connectivity)	1	2
Connector: Non-NHD Dataset	33410	3D line, polylineZ (does not connect primary network features)	2	0
Connector: Terrain breach	33405	3D line, polylineZ	1	3
Dam/weir	34300	3D polygon, polygonZ	9	0
Dam/weir	34300	3D line, polylineZ	9	0
Dam/weir	34300	3D point	9	0
Drainageway	46800	3D line, polylineZ (creates network connectivity)	1	2
Ice mass	37800	3D polygon, polygonZ	9	0
Lake/pond	39000	3D polygon, polygonZ (polygon matches hydroflattening breaklines, breakline used)	1	11
Lake/pond	39000	3D polygon, polygonZ (polygon based on hydroflattening surface, breakline edits required)	1	12
Lake/pond	39000	3D polygon, polygonZ (no hydroflattening breakline available, polygon newly captured)	1	13
Pipeline	42800	3D line, polylineZ (does not connect primary network features)	2	0
Pipeline	42800	3D line, polylineZ (creates network connectivity)	1	2
Pipeline	42800	3D line, polylineZ (creates network connectivity)	1	3
Playa	36100	3D polygon, polygonZ	1	0
Sea/Ocean	44500	3D polygon, polygonZ (polygon matches hydroflattening breaklines, breakline used)	1	11
Sea/Ocean	44500	3D polygon, polygonZ (polygon based on hydroflattening surface, breakline edits required)	1	12
Sea/Ocean	44500	3D polygon, polygonZ (no hydroflattening breakline available, polygon newly captured)	1	13
Sink	45000	3D point, pointZ	1	0
Stream/River	46000	3D line, polylineZ (creates network connectivity)	1	2
Stream/River	46000	3D polygon, polygonZ (polygon matches hydroflattening breaklines, breakline used)	1	11
Stream/River	46000	3D polygon, polygonZ (polygon based on hydroflattening surface, breakline edits required)	1	12
Stream/River	46000	3D polygon, polygonZ (no hydroflattening breakline available, polygon newly captured)	1	13
Underground Conduit	42002	3D line, polylineZ (creates network connectivity)	1	0

Table 10. Polygon features used for hydroflattening an elevation surface.

Desc	FCode
Lake/pond	39000
Sea/ocean	44500
Stream/river	46000

Table 11. Hydroflattening feature and updated code.

Hydroflattening feature	Hydroflattening short description (see Lidar Base Specification for all cases)	Elevation-derived hydrographic feature	FCode	Elevation-derived hydrographic feature 2D (polygon) description
Inland ponds and lakes	Waterbodies with a surface area of 0.8 ha (2 acres) or greater (approximately equal to a round pond 100 m in diameter) at the time of collection shall be flattened.	Lake/pond	39000	A standing body of water with a predominantly natural shoreline surrounded by land.
Inland streams and rivers	Streams and rivers of a 30 m or greater nominal width shall be flattened.	Stream/river	46000	A body of flowing water.
Tidal waterbodies	Tidal waterbodies are defined as any waterbody that is affected by tidal variations, including oceans, seas, gulfs, bays, inlets, salt marshes, and large lakes.	Sea/ocean	44500	The great body of saltwater that covers much of the Earth.
Nontidal boundary waterbodies	Boundary waterbodies are waterbodies that contain some or all of the DPA. • Boundary waterbodies may be any type of waterbody but are virtually always large in area or width. A boundary waterbody shall be represented as a polygon that follows the shore throughout the project and is then closed using arbitrary line segments as needed across the waterbody. Boundary waterbodies do not include the natural far shoreline.	Any large 2D features at the edge of the DPA. Exceptions are tidal waterbodies: sea/ocean.	39000, 43600, 46000	A 2D feature that is not wholly contained within the DPA and is therefore only partially delineated.

Table 12. Examples of acceptable ancillary datasets.

Required/ recommended	Source	Resolution	Comments	Use
Required	Subset of NHD features required for capture in the elevation-derived hydrography–AS	1:24,000 or better	Download most recent version from The National Map	Use as a guide for minimum features that must be collected.
Required	Elevation surfaces, bare-earth digital elevation model	1 meter	Should be created from bare-earth lidar points.	All features collected must match the surface of the lidar bare-earth surface.
Required	Watershed Boundary Dataset, 12-digit hydrologic units	1:24,000 or better	Download most recent version from The National Map	Use as a guide for minimum density of features that must be collected. Buffer the watershed areas to capture a complete network.
Recommended	Subset of NHD features not required for capture in the elevation-derived hydrography –AS	1:24,000 or better	Download most recent version from The National Map, or use web feature service	Use as a reference for features within the NHD with FCodes not required by elevation-derived hydrography –AS, but potentially useful for understanding the hydrology of the area.
Recommended	Intensity images from same source as lidar surfaces	1 meter	Should be created from bare-earth intensity values	From the same source as the elevation surface. Can be used as imagery. Water and wet areas are often visible.
Recommended	Leaf-off orthoimagery	≤1 meter	Image date should be as close to the lidar collection date as possible	Visible features below tree canopy. Helpful to identify roads and stream intersections.
Recommended	Leaf-on orthoimagery	≤1 meter	Image date should be as close to the lidar collection date as possible	Riparian zones are often obvious in imagery.
Recommended	Near infrared band for vegetation	≤1 meter	Image date should be as close to the lidar collection date as possible	Helpful for vegetation identification.
Recommended	Transportation layer	1:24,000 or better	State or local government data tends to be higher resolution and more current than Federal road and highway datasets	Used for identification of culvert features, and for delineation of headwater streams near roads or railroads (see “Culverts” and “Headwaters at Roads” subsections of “Special Cases” in the “Delineation of Hydrographic Features” section).
Recommended	Bridge and culvert datasets from DOT or others	1:24,000 or better	May be difficult to find for many States. Often coarser resolution but useful as a guide. National datasets exist (National Bridge Inventory, Federal Highway Administration, U.S. Department of Transportation) but are coarse	Use as a guide for culvert identification.
Recommended	Dam locations	1:24,000 or better	National dataset coarser than lidar; for example, National Inventory of Dams	Use as a guide for dam identification.
Recommended	Lidar full point cloud	1 meter	Should be from the same lidar collection	Helpful to distinguish features, or buildings that may be in flowpaths.
Recommended	Storm sewer systems and underground systems in urban areas	1:24,000 or better	Source date should be as close to the lidar collection date as possible	Use to identify subsurface connections, pipelines, culverts.
Recommended	Building footprints	1:24,000 or better	Source data should be as close to the lidar collection date as possible. Microsoft building footprints are available nationally but may be several years old. Local or State agencies may have more recently updated building footprints.	Use to route hydrography around buildings. Can be useful in areas where buildings were removed in the bare earth surface, but a pit was created as an artifact of the filtering.

Elevation-Derived Hydrography Data Acquisition Specifications: Tables

Formatted Tables in Current Revision Report

Table 1. Geometry of elevation-derived hydrography feature types.

Table 2. Attribute table structure for line hydrographic features.

Table 3. Attribute table structure for area and point hydrographic features.

Table 4. Domain values for FlowClass feature attributes.

Table 5. Domain values for Limitation feature attributes.

Table 6. FCode domain values and descriptions.

Table 7. Domain values for FClass feature attributes.

Table 8. Domain values for EClass feature attributes.

Table 9. Feature type description, associated geometry, and use classification.

Table 10. Polygon features used for hydroflattening an elevation surface.

Table 11. Hydroflattening feature and updated code.

Table 12. Examples of acceptable ancillary datasets.

U.S. Geological Survey

U.S. Department of the Interior