Evaluating the quality of the national hydrography dataset for watershed assessments in metropolitan regions

The purpose of this paper is to evaluate the "fitness for use" of the high-resolution National Hydrography Dataset (NHD) for regional watershed assessments. The Nature Conservancy's GIS tools were combined with various data sources and techniques to identify and fix four types of problems in the high resolution NHD-dangling streams, attribute errors, flow divergences, and duplicate streams. This effort generated a single-line natural flow network with correct arc-node topology, no dangling streams (with the exception of streams terminating in low relief basins), and few, if any, attribute designation problems. The revised NHD network improved on the original representation of the stream network and accompanying sub-watersheds in several ways.