A physically based model for calculating contributing area on hillslopes and along valley bottoms

Abstract

Most existing methods of calculating contributing area are unable to accurately model the pattern of contributing area on hillslopes and along valley bottoms. This paper describes a new flow algorithm, the adjustable dispersion routing algorithm (ADRA). Rather than calculating contributing area using predetermined flow characteristics that are insensitive to location in the landscape, ADRA predicts channel location and adjusts flow characteristics accordingly. ADRA increases the degree of flow divergence downslope from divides until a channel head is detected. Channel head locations are estimated on the basis of a user-defined threshold of an area-slope function. Therefore the algorithm overcomes the problems of aggregated flow on hillslopes and divergent flow along valley bottoms. The pattern of catchment area produced by ADRA was compared with similar patterns calculated using a similar flow algorithm for a variety of natural landscapes. ADRA produced patterns of contributing area that were more consistent with the theory of channel initiation.