STOCHASTIC PROPERTY OF STORAGE FUNCTION RUNOFF MODEL

Abstract

Hashino had already proposed the application of Freund's bivariate exponential density function for a design storm. At present, it is impossible to use this distribution to estimate a design flood because of its nonstationarity (average and variance) and mutual dependency. As a first step to conquer these difficulties, authors assume that the average rainfall is nonstationary and the random component of rainfall is expressed by AR (1) based on the analysis of observed rainfall. Finally, authors adopt the storage function runoff model as rainfall runoff system and propose the differential equations whose solutions provide the first four moments of discharge under the impact of mutually dependent rainfall inputs. The probability density function of discharge is easily derived by the obtained first four moments of discharge.