Database of modified routing for NHDPlus version 2.1 flowlines: ENHDPlusV2_us

This database (ENHDPlusV2_us) contains a topologically reconditioned (enhanced) version of the U.S. Environmental Protection Agency (USEPA) and the U.S. Geological Survey (USGS) NHDPlus Version 2.1 (NHDPlusV2) flowline network. The comma separated file included in this release contains routing and stream connection information, with the intention of improving accuracy and networking capabilities. The enhancements described here include corrections to inconsistencies in network and routing information, filling-in missing attribute values of associated characteristics, and revisions to diverted flow routing. The database is intended for routing purposes only; no cartographic changes were made to the original NHDPlusv2 flowline line work. Each segment of the flowline network is referenced with the unique identifier COMID. The dataset also contains attributes that identify the immediate upstream (Hydroseq and cfromnode) and downstream (ctonode) COMID in the modified flowline network. The network connectivity for flowlines ranging from headwaters to the most downstream flowline allows for the routing and aggregating of information assigned to the network. The resulting enhanced network, available in a single data file for the entire conterminous U.S., has the designation ENHDPlusV2_us.