Description: This data was created as part of the Missouri Aquatic Gap Project. This coverage contains selected arcs from the 1:100,000 National Hydrography Dataset (NHD) that was developed by the USGS and EPA. The selected arcs represent the centerlines of wide streams, impoundments, reservoirs, and wetlands as well as the segments of single line streams. An Arc/Info macro was run on the arc segments to pull select attributes from various NHD tables and attach them directly to the arc component. In many instances the NHD networks were edited and enhanced. This includes fixing areas in the 1:100,000 scale NHD that were mapped with lower stream densities than most of the nation. These areas correspond to specific 1:100,000 scale topographic maps with the same problem and can be identified by viewing the stream networks across fairly large regions as evidenced by the rectangular nature of these low density area boundaries. These areas present problems when attempting get an accurate stream order because much of the contributing network is missing. We fixed these areas of lower stream density by generating the "missing streams" using a DEM. These streams are not of the same scale or resolution as the rest of the networks. The resulting enhanced stream networks were classified into distinct stream valley segment types according to a number of variables including temperature, stream size, flow, geology, and relative gradient. Additional variables are included in the attribute table that were not used in creating the valley segment types. Because of how processing was accomplished only the primary channel interconnected stream networks are considered fully classified. In addition, the Missouri and Mississippi Rivers are not fully classified.