Abstract:
The Elevation Derivatives for National Applications (EDNA) is a multi-layered
database derived from a version of the National Elevation Dataset (NED), which
has been hydrologically conditioned for improved hydrologic flow
representation. The seamless EDNA database provides 30 meters resolution raster
and vector data layers including:
-Aspect
-Contours
-Filled DEM
-Flow Accumulation
-Flow
... Direction
-Reach Catchment Seedpoints
-Reach Catchments
-Shaded Relief
-Sinks
-Slope
-Synthetic Streamlines
The recent completion of the National Elevation Dataset (NED) and the National
Hydrography Dataset (NHD) has provided an avenue for nation-wide development of
topographically derived hydrologic data layers at a scale of 1:24,000. Some of
the benefits of a nation-wide development of hydrologic derivatives can be
summarized as:
-The development of the EDNA database would be responsive to the need for
better drainage basin boundaries for the country. The new Watershed Boundaries
Dataset (WBD) strives to identify the "best-available" watersheds boundaries
available on a national level. The development of the WBD is a joint project of
the Advisory Committee of Water Information and the Federal Geographic Data
Committee. The existing 1:250,000-scale Cataloging Unit delineations,
currently, the "best-available" watershed boundaries for the country, have
proven inadequate for many regional or local-level studies. Development of the
EDNA derived Cataloging Unit, Watershed and Subwatershed boundaries can be used
to provide high-resolution boundaries for the WBD.
-Along with development of improved, although static, Cataloging Unit
boundaries and subsequent subdivision of these units into Watershed and
Subwatershed units, the EDNA database will provide the capability of developing
drainage basin boundaries above any point within the U.S. All locations
downstream from any point in the U.S. can also be readily determined using the
EDNA derivative data layers. With this information available on a national
scale, impacts of pollutant spills can be easily traced through the network,
drainage areas above any point (not just terminal points of pre-defined
watersheds) can be determined and watershed units downstream of a point-source
discharge can be easily be identified.
-Development of the EDNA database will serve to integrate two of the USGS' key
national database, the NED and the NHD. Enhancements to both databases will be
expected as the quality control procedures used in the development of the EDNA
provide feedback to both NED and NHD. The NHD will be further enhanced by
consistency with the EDNA. Elevation-derived streamline and basin parameters
can be transferred onto the NHD following conflation with the EDNA. This will
provide valuable attributes useful in model parameterization.
[Summary provided by the USGS.] 
