A GIS-based method to calculate flow accumulation by considering dams and their specific operation time

This paper presents a new approach to calculate flow accumulation with geographic information systems (GIS). It is based on the well-known D8 single-flow algorithm that is extended to consider the trap-efficiencies of dams and their specific operation time. This allows realistic calculations of flow accumulation for any time period. The new approach is not restricted to surface water runoff but can be applied to all kinds of mass fluxes like suspended or dissolved sediment load (weighted flow accumulation). To facilitate its use, two GIS extensions for ArcView and ArcGIS have been developed. This paper presents the principles of the new approach, the functionality of the extensions and gives some applications in the fields of hydrology and sedimentology.