Flood frequency analysis based on t-copula for Johor river, Malaysia

Abstract

A copula based methodology is presented in this study for the flood frequency analysis of Johor river basin in southern Malaysia. The objective of this study was to find the best-fit distributions to the flood characteristics and finding their joint probability for flood frequency analysis. The joint dependence structures of the flood characteristics (peak flow (Qp), flood volume (V) and flood duration (D) were modelled using an Archimedean Copula (t-Copula). The distribution methods were tested to identify the best distribution that would fit the distributions of various flood characteristics. Based on Kolmogorov-Smirnov (K-S) test the Generalized Pareto distribution is the best-fit distribution for peak flow. On the other hand, General Extreme Value (GEV) is the best-fit distribution for the flood duration and flood volume. The best fit distributions were then used to develop the joint Cumulative Distribution Function (CDF) of the flood characteristics based on t-Copula. Peak flow-volume, volume-duration and peak flow-duration pairs were found to be negatively related. It is expected that the bivariate distributions formulated is useful for flood risk assessment and design of hydraulic structures in Malaysia. © 2013 Asian Network for Scientific Information.