Algorithm for Precise Drainage‐Basin Delineation

Abstract

Computer‐based terrain models have become increasingly popular as a tool for automating much of the geometrical data acquisition necessary for hydrologic analyses. An algorithm is presented that uses triangulated irregular networks (TINs) to accurately delineate drainage‐basin boundaries. Boundary delineation can be performed for areas that drain to individual points or stream networks defined on the TIN. A special feature of the algorithm is that the segments of the stream network need not correspond to channel edges. This allows greater flexibility in defining stream networks on the TIN and makes it possible to apply the boundary delineation algorithm to urban areas where the stream networks may be dominated by manmade structures such as streets and canals or to rural areas where the terrain exhibits little relief. Once the basin boundaries are established, geometric parameters such as basin areas, slopes, and maximum flow distances are easily computed. These tools can be combined with hydrologic modeling software such as HEC‐1 to create a comprehensive hydrologic modeling environment.