Apr 27, 2021 Generalizing the NHDPlus HR for National Applications

Topic: Generalizing the NHDPlus HR for National Applications

Presenters: Cindy McKay, Richard Moore, Al Rea

00:02:04 NHDPlus HR National Data Release - Al Rea

00:10:15 EPA Considerations - Shelley Cawley (EPA)

00:13:08 Generalization - Cindy McKay

00:37:24 Disconnected Networks - Al Rea & Rich Moore

EPA has been sponsoring research into how to generalize the NHDPlus HR to a level of detail similar to the older Medium Resolution (1:100,000 scale) NHDPlus Version 2, while retaining the network addresses (ReachCodes and Measures ) of the NHD High Resolution. This will support national modeling efforts, while consolidating network-referencing efforts to a single addressing framework based on NHD High Resolution.

A generalized version of NHDPlus HR is being developed nationally and is nearing completion. The dataset has a stream network similar in density to the NHDPlus V2, and has catchments dissolved to match the network. The new dataset, however, has a lot more disconnected drainage than NHDPlus V2. The presentation will show methods the team is developing to deal with this issue, both in the short term and in the longer term. The presentation also will describe how the numbers of features and feature density variations are being handled.