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Differences Between EDH and 3DHP Data

By 3D Hydrography Program

Elevation-Derived Hydrography (EDH) is a general term used for any digital representation of surface water features like streams, lakes, and other hydrographic features that are derived from an elevation surface or Digital Elevation Model (DEM). EDH is created using algorithms that identify channels and depressions in the DEM that represent natural surface-water flow paths.

EDH and 3DHP Compared 

EDH and 3DHP are not equivalent datasets.  EDH is an input dataset to 3DHP and not all EDH can be ingested into the 3DHP which requires that the EDH meets the requirements outlined in the USGS EDH Acquisition Specifications webpage. EDH data collected for 3DHP also must be collected into a specific EDH schema provided by USGS. To ensure integration with the national datasets, the EDH must be derived from 3D Elevation Program 1-meter DEMs or 5-meter DEMs from IfSAR in Alaska. The DEMs must also be projected to a specific coordinate reference system before the EDH is produced. These requirements ensure that the EDH is integrated, both horizontally and vertically, with the nationally consistent 3DEP elevation data to support the USGS 3D National Topography Model. 

 

EDH data lacks important attribution - like official feature names, and cross-dataset identifiers or “Mainstem IDs” - that are added when the EDH data are ingested into 3DHP.  The table below is not comprehensive but identifies some key features and attributes present in 3DHP but not in EDH.  

 

Attribute EDH 3DHP
Improved geometric accuracy ✔ ✔
Vertical and horizontal integration with 3DEP elevation ✔ ✔
Direction of flow ✔ ✔
Cross-dataset identifiers (mainstem IDs) ✘ ✔
Official Name identifier from Geographic Names Information System (GNIS) ✘ ✔
Strahler stream order ✘ ✔
Hydrographic sequencing information ✘ ✔
Divergence information ✘ ✔
Catchments ✘ ✔
Integrated Drainage areas (future 3DHP enhancement) ✘ ✔
Hydro-enforced elevation surface ✘ ✔

 

During ingestion to 3DHP, EDH line features are converted to the 3DHP flowline feature schema, point features are converted to 3DHP hydrolocation feature schema, and polygons are converted to 3DHP waterbody feature schema. In addition, flow network derivative information is calculated and linked to the flowlines; key point features like the locations of catchment outlets and flow divergences are derived; and 3DHP catchment features are generated.  In the future, 3DHP catchment features will be aggregated into 3DHP drainage area features similar to the hydrologic units in the Watershed Boundary Dataset. A crosswalk table showing how EDH features relate to 3DHP features is available from the 3DHP product specifications webpage. 

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