About

Sources/Usage: Public Domain. View Media Details

Including:

• Aspect
• Contours
• Filled DEM
• Flow Accumulation
• Flow Direction
• Reach Catchment Seedpoints
• Reach Catchments
• Shaded Relief
• Sinks
• Slope
• Synthetic Streamlines

Hydrologically conditioned elevation data, systematically and consistently processed to create hydrologic derivatives,can be useful in many topologically based visualization and investigative applications. Drainage areas upstream or downstream from any location can be accurately traced facilitating flood analysis investigations, pollution studies, and hydroelectric power generation projects. 

Sources/Usage: Public Domain. View Media Details

Background

Increasingly, many local, state and federal agencies that have the mandate for management of water resources are finding that their needs are not being met by existing digital data sets. Current national coverage of digital data sets, such as drainage basin boundaries and consistent elevation-derived parameters, do not exist or are not of a suitable scale or consistency to allow management of small or mid-size watersheds. This problem becomes more significant as the management of water resources, both in terms of quantity and quality, is becoming more and more based on the watershed scale.

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.

Additional information about the Elevation Derivatives for National Applications (EDNA) database is available online at: USGS EROS Archive - Digital Elevation - Elevation Derivatives for National Applications (EDNA) Seamless Three-Dimensional Hydrologic Database