Kunihide Uchijima

A study on subcatchment scale for a distributed runoff model

Abstract Physically-based distributed runoff models are more advantageous than concentrated conceptual models for predicting the hydrologic response of ungauged basins and the changing response resulting from changes in land-use. In constructing distributed models, the river basin must be divided into reasonable smaller subcatchments corresponding to a characteristic scale for rainfall-runoff response. Thus, one of the still-unsolved problems in distributed models is the estimation of the appropriate subcatchment scale. This paper focuses only on the appropriate subcatchment scale considering the channel network geomorphology, although the effects of subcatchment scale on the overall river basin response are important. For this purpose, some new stochastic functions are proposed for discussing the hydrologic response of channel networks. By applying these functions into a simplified distributed runoff model, the relationship between the hydrologic response of the river basin and variation of the channel network geomorphology is shown.