Modeling the Distributions of Flood Characteristics for a Tropical River Basin

Understanding the distribution of flood variable is crucial for the purposes of flood prediction and hydraulic design. Three major parameters that are useful to describe a flood event are peak flow or flood peak, flood volume and flood duration. This study aimed at exploring the statistical distribution of these parameters for Johor River in south of Malaysia. Hourly data were recorded for 45 years from Rantau Panjang gauging station. The annual flood peak was selected from the maximum flow in each water year (July-June). Five probability distributions namely Gamma, Weibull, Exponential, Gumbel and Generalize Extreme Value (GEV) were used to model the distribution of flood parameters. Kolmogorov-Smirnov and chi-squared goodness-of-fit tests were used to evaluate the best fit. Goodness-of-fit tests at 5% level of significance indicated that all the models can be used to model the distribution of peak flow, duration and volume. However, the Exponential distribution is the most suitable model when tested with the Kolmogorov-Smirnov test whereas GEV is the best when chi-squared test was used. The result can be used as a basis to improve flood frequency analysis for Malaysian rivers.