This stream layer is a modified version of the USGS NHDPlus Version 2 (NHDPlusV2) stream flowline data. The original geospatial data included in the NHDPlusV2 are intended to support a variety of water-related applications. [U.S. Environmental Protection Agency (USEPA) and the U.S. Geological Survey (USGS)]. This modified version is intended to be used with the STARS and SSN statistical toolsets (Peterson E.E. and Ver Hoef J.M. 2014, Ver Hoef J.M. and Peterson E.E. 2010). The NHDPlusV2 stream network was simplified by removing braids and diverging channels, as well as modifying confluences with more than two tributaries (complex confluences). Locations where more than 2 segments joined at a stream junction were separated and snapped to a newly created node more than 25 meters downstream. Where possible, the segment with the smallest contributing area (TotDASqKM) value was moved. Where multiple stream segments converged into sinks, the terminal end nodes were moved 25 meters apart. In addition, segments where nodes created downstream divergences or where stream flow converged were separated as deemed most appropriate. This simplification of the stream network supports statistical calculations with the STARS Toolbox while maintaining the majority of network features for modeling purposes.

Peterson E.E. and Ver Hoef J.M. (2014) STARS: An ArcGIS toolset used to calculate the spatial information needed to fit spatial statistical models to stream network data. Journal of Statistical Software, 56(2).

Ver Hoef J.M. and Peterson E.E. (2010). A moving average approach to spatial statistical models of stream networks. The Journal of the American Statistical Association, 489: 6-18

More Information: http://www.fs.fed.us/rm/boise/AWAE/projects/NationalStreamInternet.html