Submitted to: Demonstration Erosion Control Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 1, 1996
Publication Date: N/A
Technical Abstract:
Automated drainage identification and watershed segmentation from grid Digital Elevation Models (DEM) is a feature that is found in many GIS packages. However, problems still exist in the determination of realistic and topographically consistent drainage patterns over sinks and flat surfaces in DEMs. Also, the identification of the drainage network topology from images and the determination of geometric characteristics of individual subcatchments is rarely found in commercial GIS packages. Yet, proper drainage identification and automated parameterization of subcatchments from DEMs is often necessary for distributed hydrologic/hydraulic model applications. This paper presents improved methodologies to generate realistic and topographically consistent drainage patterns over sinks and flat surfaces in DEMs; describes an identification of network topology that overcomes grid dependency; and, outlines the parameterization of subcatchments for the Wooding open-book subcatchment representation. As a result the extent and number of sinks created by narrow flow obstructions in DEMs are reduced by breaching narrow sink outlets; the drainage indeterminacy over flat surfaces in DEM is resolved by projecting the topographic characteristics surrounding the flat surface into the flat surface; and, the dependance of the network topology on grid size is overcome by decomposing multiple junctions at the grid level into a sequence of single junctions. Finally, the calculation of hydraulically representative catchment length, width, and slope of Wooding open-book planes representing irregularly shaped subcatchments is based on weighted flow path characteristics of all flow paths within the subcatchment.
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