Takahiro YAMAMOTO

Calculation of Design Flood by using a Random Cascade Model

Minjiao LU


The objective of this study is to investigate the applicability of random cascade model(RCM) to estimation of design flood. For this purpose, a new cascade generator which keeps the rainfall amount unchanged is proposed in this study. The parameters of this generator is determined by analyzing the 10�|minute rainfall data from April 1994 to December 2003 at all seven AMeDAS sites in Kagawa Prefecture. By using parameters suitable for design rainfall, the RCM is applied Doki river to generate hyetographs from design rainfall. The hyetographs are then inputed into a runoff model to compute the hydrograph and peak dischaege. It is shown that the mean peak discharge is quite near to current design flood. Furthermore, It is to calculate that maximum discharge distribution corresponding to the distribution of annual maximum daily rainfall by using the RCM. The maximum discharge is calculated from disaggregated hyetographs by using a runoff model. This technique is applied to the Doki river basin, a small basin, where the influence of human activities is very limited. The observed discharge of annual maximum from 1976 to 1998 was used to verify the calculated distribution of maximum discharge. It is shown that calculated distribution of maximum discharge reproduced well. Moreover, the cover ratio of the conventional method to compute design flood is evaluated.