Submitted to: American Society of Civil Engineers Hydraulic Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 1, 1996
Publication Date: N/A
Interpretive Summary: Environmental processes such as rainfall-runoff and soil erosion are frequently simulated using computer programs which require the description of landscape topographic properties. This paper describes an automated approach that uses a digital representation of the landscape. The paper defines a procedure to compute representative hillslope length, width and slope that are needed by rainfall-runoff and erosion computer programs. The presented procedure extends the application of these rainfall-runoff and erosion computer program to many situations which previously were impractical to evaluate due to the large amount of required landscape data needed. This procedure is much faster and provides more precise and reproducible measurements than the traditional manual techniques.
Technical Abstract: Numerical algorithms are presented to estimate the length, width and slope of rectangular planes representing irregularly shaped overland contributing areas defined on raster Digital Elevation Models (DEM). The strength of the procedure lies in that each flow path on the raster overland area is considered in the determination of the representative value for the entire rectangular plane as opposed to relying on a lumped, single flow path approach. The flow path parameters required by the algorithms are derived from rasters maps of elevation (DEM), flow direction and upstream area. Qualitative cause-effect relations between flow path and runoff characteristics are used to emphasize those flow paths that are important to runoff formation and propagation. Based upon these considerations, the plane length and slope are computed as a weighted mean flow path length and slope over all flow paths of the overland area. Several alternative weighing factors are proposed. Based on area conservation, the plane widt is computed as the overland area divided by the plane length.