This paper describes a method of flood runoff analysis by the applied series tanks model and the applicability of runoff models using optimum identification of their model parameter .
The parameter identification of the series tanks model by M. Sugawara as the lumped parameter model became possible through development of mathematical optimization techniques given by the study of S. Kobayashi and T. Maruyama, A. Nagai and M. Kadoya. But, there is a limit in forecasting change of the series tank model parameter accompanying the development of a river basin. While, the rainwater flow method is a distributed parameter model that is characterized by the disposal point to discussion of the hydrological effects by the development of a river basin. But, an analysis by the rainwater flow method involves some problems unsolved in the estimation method of effective rainfall for forecasting of flood runoff.
Therefore, the two methods of flood runoff analysis are proposed by using the parameters of the applied series tanks model having one to one correspondence to the parameter of the rainwater flow model. One of the models is the applied series tanks model of a lumped storage type and the other is ones of a distributed storage type. Next, the applicability of the two runoff models is examined to the observed hydrologic data in the Shimokari basin of 1.32 <km>^^^2 and in the Uchida basin of 0.107 <km>^^^2 by searching their optimum model parameters. The Standardized Powell method is used to the optimum identification of their model parameters.
As the result, it is pointed out that the reproducibility of observed hydrograph is good for several floods and the usefullness of the proposal models is verified. Also, it is found that the expression for their model parameters is related to the mean slope length of a basin model.