Elevation-Derived Hydrography Acquisition Specifications: Tables

By NGP Standards and Specifications

Elevation-Derived Hydrography Acquisition Specifications

Tables from Elevation-Derived Hydrography Acquisition Specifications Report - Techniques and Methods 11–B11

Return to EDH Acquisition Specifications Table of Contents

Formatted Tables in Current Revision Report

Elevation-Derived Hydrography Acquisition Specifications 2022 rev. A (pdf)

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

Table 2. Attribute table structure for hydrographic feature.

Table 3 A. Domain values for feature attributes.

Table 3 B. FCode domain values and descriptions.

Table 4. Polygon features used for hydroflattening an elevation surface.

Table 5. Hydroflattening feature and updated code.

Table 6. Feature type description, associated geometry, and use classification.

Table 7. Examples of acceptable ancillary datasets.

Table 1. Geometry of elevation-derived hydrography feature types.
Feature type	Format	Geometry
Point	Vector shape	3D point, pointZ
Line	Vector shape	3D line, polylineZ
Polygon	Vector shape	3D polygon, polygonZ

Table 2. Attribute table structure for hydrographic feature.
Attribute description	Item name	Item	Item type	Item precision
Feature class (NHD)	FClass	Integer	Short	4
Feature class (elevation)	EClass	Integer	Short	4
Feature code (NHD)	FCode	Integer	Long	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

Table 3 A. Domain values for feature attributes.
Domain value	Feature attributes
FClass
1	NHD feature (will be used for conflation).
2	Non-NHD feature (outside of collection criteria).
9	Nonhydrography feature (elevation dataset limitation).
EClass
0	Not used for elevation derivatives. May be used for network connectivity.
1	Used for hydroflattening (3D polygon).
2	Linear hydrographic features that follow the elevation surface.
3	Features below ground level – includes connectors, culvert connectors, and terrain breach connectors. May be used for hydro-enforcement.
9	Elevation dataset limitation.

Table 3 B. FCode domain values and descriptions.
FCode	Desc
0	User-defined feature¹
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
43600	Reservoir
44500	Sea/ocean
45000	Sink/rise
46000	Stream/river
46800	Drainageway¹
55800	Artificial path
991	Low-confidence area (predetermined)
992	Low-confidence area (sparse bare earth)
993	Low-confidence area (snow covered)

¹New feature.

Table 4. Polygon features used for hydroflattening an elevation surface.
Desc	FCode
Lake/pond	39000
Reservoir	43600
Sea/ocean	44500
Stream/river	46000

Table 5. 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.
		Reservoir	43600	A constructed basin formed to contain water or other liquids.
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 6. Feature type description, associated geometry, and use classification.
Desc	FCode	Geometry type	EClass Domain value	EClass Feature attribute	FClass Domain value	FClass Feature attribute
Artificial path	55800	3D line, polylineZ	2	Hydrographic feature used for elevation purposes, other than culverts or those used for hydroflattening	1	NHD feature (will be used for conflation).
Canal/ditch	33600	3D line, polylineZ (does not connect primary network features)	0	Not used for elevation derivatives	2	Non-NHD feature (outside of collection criteria).
		3D line, polylineZ (creates network connectivity)	2	Hydrographic feature used for elevation purposes, other than culverts or those used for hydroflattening	1	NHD feature (will be used for conflation).
Connector	33400	3D line, polylineZ	3	Hydrographic feature used for elevation purposes, other than culverts or those used for hydroflattening	1	NHD feature (will be used for conflation).
Connector: Culvert		3D line, polylineZ	3	Features below ground level. May be used for hydro-enforcement	1	NHD feature (will be used for conflation).
Connector: Indefinite surface		3D line, polylineZ	2	Linear hydrographic features that follow the elevation surface	1	NHD feature (will be used for conflation).
Connector: Non-NHD Dataset		3D line, polylineZ	0	Not used for elevation derivatives	1	NHD feature (will be used for conflation).
Connector: Terrain breach		3D line, polylineZ	3	Features below ground level. May be used for hydro-enforcement	1	NHD feature (will be used for conflation).
Dam/weir	34300	3D point, pointZ	0	Not used for elevation derivatives	2	Non-NHD feature (outside of collection criteria).
		3D line, polylineZ	0	Not used for elevation derivatives	1	NHD feature (will be used for conflation).
		3D polygon, polygonZ	0	Not used for elevation derivatives	1	NHD feature (will be used for conflation).
Drainageway	46800	3D line, polylineZ	2	Hydrographic feature used for elevation purposes, other than culverts or those used for hydroflattening	1	NHD feature (will be used for conflation).
Ice mass	37800	3D polygon, polygonZ	0	Not used for elevation derivatives	1	NHD feature (will be used for conflation).
Lake/pond	39000	3D polygon, polygonZ	1	Used for hydroflattening	1	NHD feature (will be used for conflation).
Low-confidence area (predetermined)	991	3D polygon, polygonZ (accurate z-values not required)	9	Elevation dataset limitation	9	Nonhydrography feature (elevation dataset limitation).
Low-confidence area (snow covered)	993	3D polygon, polygonZ (accurate z-values not required)	9	Elevation dataset limitation	9	Nonhydrography feature (elevation dataset limitation).
Low-confidence area (sparse bare earth)	992	3D polygon, polygonZ (accurate z-values not required)	9	Elevation dataset limitation	9	Nonhydrography feature (elevation dataset limitation).
Pipeline	42800	3D line, polylineZ (does not connect primary network features)	0	Not used for elevation derivatives	1	NHD feature (will be used for conflation).
		3D line, polylineZ (creates network connectivity)	2	Hydrographic feature used for elevation purposes, other than culverts or those used for hydroflattening	1	NHD feature (will be used for conflation).
Playa	36100	3D polygon, polygonZ	0	Not used for elevation derivatives	1	NHD feature (will be used for conflation).
Underground Conduit	42002	3D line, polylineZ (creates network connectivity)	0	Not used for elevation derivatives	1	NHD feature (will be used for conflation).

Table 7. Examples of acceptable ancillary datasets.
Required/ recommended	Source	Resolution	Comments	Use
Required	Subset of NHD features required for capture in the EDH–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 EDH–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 EDH–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.