Development of empirical models from rainfall-intensity-duration-frequency curves for consecutive Days maximum rainfall using GEV distribution

Abstract

A statistical analysis of 27 years rainfall data of Kumulur region in Trichy district of Tamil Nadu was conducted using Gumbel distribution and Generalised Extreme Value (GEV) distribution. The method of L- moments was used for determining the parameters for both distributions. Annual maximum rainfall for 2, 3,4, 5 and 7 consecutive days for the available 27 years were analysed and the return levels for four assumed return periods viz. 2, 5, 10 and 25-years were calculated using both the probability distribution functions. The goodness-of-fit of the distributions were analysed by conducting a chi-square test for the observed and expected return levels. The consecutive days maximum rainfall data found to fit best with generalised extreme value distribution. The Empirical Reduction Formula proposed by the Indian Meteorological Department was used for the calculation of short duration for 1-hr, 2-hr, 3-hr, 5-hr, and 8-hr. From the derived short duration rainfall depths, the intensity of the rainfall was calculated. The rainfall Intensity-Duration-Frequency (R-IDF) curves were plotted for the region and the corresponding empirical models were derived.