Stochastic Flood Analysis in a Region of Mixed Generating Processes

Abstract

In southwestern British Columbia there exists a transition from winter rain generated floods on the west coast to spring snowmelt generated floods on the Interior Plateau. Each process gives rise to distinct flood types characterized by their magnitude, timing and frequency. The region of transition between the two single process-dominated areas displays a progressive mixture of both types. Existing stochastic floods prediction models are applied to the partial duration and annual flood series of seventeen drainage basins. In all cases the fit of observed to predicted data is found to be adequate. The parameters of the stochastic models are clearly indicative of both the differing characteristics of each generating process and the smooth geographic transition from one flood regime to another. It is proposed that the use of partial series is superior to traditional annual flood series in its practical definition of flooding; provision of a standardized method of analysis which is catholic in its applicability, and parameters which are easily estimated and interpreted.