FLOW DIRECTION AND BRANCHING GEOMETRY AT JUNCTIONS IN DENDRITIC RIVER NETWORKS

Automatic determination of flow direction from a partial view of a drainage network is a problem, notably in remote sensing. The main approach to determining which river link is pointing downstream uses spatial reasoningbased on local features at junctions. Theoretical and empirical works on junction angles suggest that the twoconsecutive links which bound the most acute angle are the upstream links. This rule was tested using 2279 riverjunctions digitized from 19 dendritic drainage networks and was correct in nearly 90% of the cases. This resultis better than that obtained from the decision table designed by Haralick, Wang et al. (1985) for the same purpose. © 1990 by Association of American Geographers.