FREQUENCY ANALYSIS OF RAINFALL FOR FLOOD CONTROL IN PATANI, DELTA STATE OF NIGERIA
The Niger Delta Region of Nigeria is within the mangrove forest region and is crisscrossed by series of streams and creeks. As a result of the high rainfall volume within this region there is a tendency for severe flooding to occur. These flood events have severe consequences on lives and properties. It is therefore necessary to carry out a flood frequency analysis in this area in order to predict the potentials for the occurrence of flooding and take necessary measures for their remediation. In this study, peak monthly rainfall for thirty three years from 1981 – 2013 were acquired for Patani area in the Niger Delta region of Nigeria from NIMET and CBN. Five probability distributions, namely Normal, Log normal, Log-Pearson, Gumbel and Foster’s Type -1 were selected for frequency analysis of the precipitation data using return periods of 2, 5, 10, 25, 50, 100 and 200 years respectively. The predicted values were subjected to goodness of fit tests using ANFIS tool in the MATLAB 7.0 software. The results of the tests and analyses show that the Gumbel Distribution best describes the precipitation data for the region and can therefore be used for the prediction of flooding within the study area followed by the Foster’s Type- I distribution. The Normal Distribution was on the other hand found the least suitable for describing the precipitation data for Patani area.