Assessing Adequacy of Probability Distribution for Development of IDF Relationships for Mandla and Jabalpur

Rainfall intensities of various frequencies and durations are the important parameters for the hydrologic design of storm sewers, culverts and other hydraulic structures. This can be achieved by rainfall intensity-duration-frequency (IDF) relationship, which is determined through rainfall frequency analysis. This paper exemplifies the use of Gumbel and Frechet distributions for modelling annual nhourly maximum rainfall for different duration of ‘n’ such as 1-hour (hr), 2-hr, 3-hr, 6-hr, 12-hr, 18-hr, 24-hr, 48-hr and 72-hr recorded at Mandla and Jabalpur rain-gauge stations. Order Statistics Approach is applied for determination of distributional parameters for estimation of rainfall and development of IDF relationships for different return periods. Goodness-of-Fit (GoF) test involving Kolmogorov-Smirnov test is used for checking the adequacy of fitting of distributions to the recorded data. Model Performance Indicators (MPIs) such as root mean square error and coefficient of determination are used to analyse the performance of IDF relationships given by Gumbel and Frechet distributions. Based on GoF test results and MPIs values, the study suggested that the developed IDF relationships by Gumbel distribution are better suited for estimation of rainfall intensity at Mandla and Jabalpur.