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Track: Water Resources
Silvia Terziotti
U.S. Geological Survey
3916 Sunset Ridge Drive
Raleigh, NC 27607
Telephone: 919-571-4090
Fax: 919-571-4041
E-mail: seterzio@usgs.gov
Using Theissen Polygons and Routes To Create Stream Centerlines from EPA River Reach File 3
Defining Issue: The generation of single-line streams from water bodies and double-line streams for an entire state is a time-intensive task. In order to generate a satisfactory digital elevation model (DEM) using ArcInfo software's TOPOGRID function, a single-line stream network is necessary to control the interpolation process and to represent a hydrologically sound surface. The resultant DEM is appropriate for watershed delineation, flow path and accumulation analysis, and generation of other basin-dependent characteristics of a study area. GIS Solution: The North Carolina District of the U.S. Geological Survey has developed programs to process the Environmental Protection Agency's 1:100,000-scale River Reach File 3 (RF3) using an automated process of Theissen polygon generation and routing from intersections of streams to the outflow of points of water bodies. Methodology: Using attributes within the RF3 file, stream segments that composed river banks, shorelines, lakes, and other double-line
stream features are identified. These double-line streams or water bodies are closed using interactive editing sessions. Theissen polygons are created every 25 meters along the double-line stream and clipped to the polygons. For each polygon that a double-line stream defines, a route is created by selecting a path from each node (representing an intersection with a single-line stream) to the outflow point of the polygon. The generated stream centerlines are then placed into a coverage containing all other single-line streams. The dangling stream segments with nodes matching the double-line stream polygon nodes are extended to meet the new centerline stream. Some interactive editing is necessary to complete the connectivity of the streams. The stream network is then checked for connectivity, and all stream segments are oriented in the downstream direction. The coverage is now ready for use in TOPOGRID. Software: This application was written using ArcInfo ARC Macro Language (AML). The purpose of
this paper is to describe the functions of this program and to outline its use with U.S. Environmental Protection Agency River Reach File 3.
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