Abstract

Improved DEM Derivatives in the NHDPlus Version 2
Track: Water Resources
Authors: Alan Rea, Craig Johnston, Richard Moore

The National Hydrography Dataset Plus (NHDPlus) has provided a ready-to-use suite of raster and vector geospatial datasets nationally (except for Alaska) since it was released in 2006. This year, 2012, a refresh of the NHDPlus, known as Version 2, has been released. NHDPlus Version 2 includes a number of improvements in the raster processing of digital elevation model (DEM) hydrologic derivatives. In addition to improvements in three primary ingredient datasets, the National Hydrography Dataset (NHD), the National Elevation Dataset (NED), and the Watershed Boundary Dataset (WBD), the DEM processing has been updated to improve handling of water bodies, non-contributing areas, and coastlines. Additional automated steps have been added, as well as the capability to control hydro-conditioning and catchment generation on individual flowlines. A stepping process is used to ensure the correct direction of flow in large, low-gradient streams. Also, much greater detail is included for areas in Canada and Mexico.