LUMPING OF A PHYSICALLY-BASED DISTRIBUTED MODEL FOR SEDIMENT RUNOFF PREDICTION IN A CATCHMENT SCALE

This paper proposes a lumping method of a distributed rainfall-sediment-runoff model. The lumping method is divided into two parts: lumping of the kinematic wave distributed rainfall-runoff model, and lumping of the distributed sediment transportation model that takes into account for erosion and deposition by raindrop and overland flow. A kinematic wave distributed rainfall-runoff model is lumped based on the assumption of steady state conditions. Soil detachment and deposition from an entire catchment are simulated by the balance between the current sediment storage and the maximum sediment storage, which is estimated from a distributed rainfall-sediment-runoff model as a function of total surface water storage of the lumped rainfall-runoff model. The proposed lumping method is examined by comparing water and sediment discharges simulated by the distributed and the lumped rainfallsediment-runoff models in the Lesti River Basin, Indonesia.