COMPARISON OF SIX EXTREME FLOOD ESTIMATION TECHNIQUES FOR UNGAUGED WATERSHEDS IN COASTAL BRITISH COLUMBIA

Abstract

A comparison of six techniques for the estimation of peak flow from ungauged watersheds in coastal British Columbia is carried out. The techniques compared are a new physically-based stochastic-deterministic procedure (Loukas and Quick, 1994a), the British Columbia Ministry of Environment and Parks method, a statistical method based on the Bayes theorem and proposed by Russell (1982), and the well known regional techniques, the Index Flood method, the method of Direct Regression of Quantiles, and the method of Regression of the Distribution Parameters. The techniques are applied to a coastal British Columbia watershed, the Sarita River watershed which is located on the west coast of the Vancouver Island. Estimated the peak instantaneous and daily flows are compared with observed flows. The analysis shows that the stochastic-deterministic procedure, the B.C. Environment method, and the Bayesian method give acceptable results. In particular, the stochastic-deterministic procedure requires very limited infor...