COMPUTER PROGRAM FOR MODELLING RAINFALL INTENSITY DURATION FREQUENCY (IDF) RELATIONSHIPS BY SHERMAN’S METHOD FOR ILORIN AREA IN NIGERIA

A computer program was developed for the modelling of rainfall data for a period of 30 years (1981-2010) for Ilorin area using a MATLAB software. The data was analyzed by sorting and ranking the maximum rainfall depths with their corresponding depths and their return periods. The rainfall depths were converted to rainfall intensities. An algorithm was developed in form of a flowchart which guided the development of computer program using Sherman’s method. Values of rainfall intensities with corresponding durations and return periods were exported to the MATLAB program for modelling of station constants and simulation of IDF curves for Ilorin area. The station constants were obtained as n = 0.5707, c = 131.0144, and m = 0.3425 for Ilorin area respectively. These were used to produce IDF curves and mathematical model for Ilorin area.