Applicability of kriging to regional flood estimation problem in Eastern Australia

![CDATA[Design flood estimation in ungauged catchments is a common problem in hydrology. Regional flood frequency analysis (RFFA) is widely used in design flood estimation at ungauged sites, which attempts to transfer flood characteristics from gauged catchments to ungauged ones. The most commonly adopted RFFA methods in Australia in the past included the Index Flood Method, Quantile Regression Technique and Probabilistic Rational Method; however, the new Australian Rainfall and Runoff (ARR) recommends a Parameter Regression Approach based on Log Pearson Type 3 distribution. This paper presents development of a new RFFA method in Australia based on ordinary kriging. It uses data from 558 gauged catchments from Victoria, New South Wales and Queensland States of Australia. These catchments are small to medium in size, with an upper limit of 1000 km2. Based on a leave-one-out validation technique, it has been found that the relative error values in design flood estimates by kriging are in the range of 28 to 36%, which are smaller than Australian Rainfall and Runoff (ARR) recommended RFFE Model. However, kriging shows a relatively higher degree of bias than the RFFE Model. The findings of this study will be useful to enhance the RFFE Model in Australia in near future by applying kriging.]]