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August 15, 2022

Users of the USGS National Hydrography Dataset will now be able to more easily create hydrography information from elevation data from 3D Elevation Program (3DEP) products. These improvements come from new specifications that allow for consistent analysis of data and make it easier to align hydrography features like rivers and lakes to elevation surfaces. 

To better keep pace with these ongoing changes, the USGS created a new webpage to share updates with users. All updates to the National Hydrography Dataset will receive review and approval by the USGS Hydrography Specifications Review Board before publication to the new webpage. 

These updates to the specifications came from early efforts to derive hydrography from 1-meter 3DEP data in the Contiguous United States and 5-meter data in Alaska. Initial changes were made to the Elevation-derived Hydrography Acquisition Specification and the Elevation-Derived Hydrography—Representation, Extraction, Attribution, and Delineation (READ) Rules published as USGS Techniques and Methods reports in 2020. These new updates represent even more refinements to the specifications. 

The Elevation-Derived Hydrography Acquisition Specifications describe requirements for the capture of hydrographic features from 3DEP products. The specifications provide a consistent data structure, define the minimum set of features required, and describe the horizontal and vertical positional requirements for alignment of hydrography features to the elevation surface.  

Revision Notes 

The latest version of specification was released on May 31, 2022 and supersedes previously published versions. This release, named 2022 rev. A, reflects a new version numbering convention designed to track revision history and to clearly identify the year and sequence of each release. Versions are now labeled with "YYYY rev. L" where YYYY is the year of the release and L is a letter corresponding to the order of the release. Elevation-derived Hydrography specification 2022 rev. A is the first release of the specification in 2022. A second release with new revisions would be named "Elevation-derived Hydrography specification 2022 rev. B". 

Revisions reflected in version 2022 rev. A include removal of “Area of Complex Channel” features from the specification, an update to the definition for “Drainageway”, the addition of four new connector feature type codes (FCodes), and the addition of an underground conduit FCode. Detailed information about revisions implemented are listed at the top of the pdf format of the specification linked here.  

Revisions for the companion Elevation-Derived Hydrography Representation, Extraction, Attribution, and Delineation (READ) Rules which describe the parameters for the portrayal of hydrographic features as derived from elevation data have not yet been released.  

More Information 

More information about the 3D Hydrography Program initiative is available online. The National Hydrography Dataset (NHD) represents the water drainage network of the United States with features such as rivers, streams, canals, lakes, ponds, coastline, dams, and streamgages. The NHD is the most up-to-date and comprehensive hydrography dataset for the Nation.

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