Runoff Model for Flood Forecasting

Abstract

The formation process of flood hydrograph in a river basin can be expressed by the combination of the conversion process from rainfall to runoff in divided sub-basins and the concentration process of the runoffs in a stream net. The objective of this paper is to develop a synthetic method of flood estimation based on such a concept. The tank model is employed for the conversion process and the modified time-area-concentration diagram for the concentration process. The hydrograph at the outlet of a basin is given by the convolution integral of the output from the tank model and the modified time-area-concentration diagram. The method of calculation of flood hydrographs is applied to five actual basins, and the values of parameters of the tank model are identified for each basin. After investigating the relation between the identified parameters and the geological features of the basins, several calculations on other basins are carried out for verification of the relation. Then, a synthetic method of flood estimation can be introduced for flood forecasting.