Fall NEARC 2018

AUTHORS: Scott Hoffman, USGS, Pennsylvania Water Science Center

ABSTRACT: The National Hydrography Dataset (NHD) is a digital geospatial dataset that maps the surface water of the United States. The NHD High Resolution (HR), at 1:24,000-scale or better, is the most up-to-date and detailed hydrography dataset for the nation, supported and maintained by the U.S. Geological Survey. The NHD medium resolution, at 1:100,000-scale, is a legacy dataset with the US EPA acting as the primary custodian supporting modeling applications. Both datasets are part the national framework for NHDPlus: NHDPlus_Version2 at the 1:100,000 scale, and NHDPlusHR at the 1:24,000 scale. Critical to the accuracy and function of each dataset is the correct geometry of the stream network. Errors in the network cause miscalculations for various parameters including drainage area and stream miles. The incorrect placement of Artificial Path or Connector features can be the main cause for stream network errors in NHDPlus datasets used in state-specific StreamStats applications. In Pennsylvania, the impact of geometry errors in NHDPlus_Version2 and NHDPlusHR will be discussed with selected examples from both datasets. Also shared will be some of the terminology used in the recently released NHDPlusHR Mark-up Tool to submit corrections into the NHD database.