Precipitation Intensity-Duration Occurrence Models Development for Designated Locations in the Southern Humid Rain Forest Zones of Nigeria

This research work examined the tendencies and patterns in the rainfall in carefully chosen localities of Southwest and South-South Nigeria. Rainfall data from 1983-2014 in Ibadan, Lagos, Benin, Calabar, Port Harcourt and Warri were used for this study. Standard deviation, mean, coefficient of skewness, coefficient of kurtosis, coefficient of variation and standardized anomaly index were engaged to analyze the data and describe the distribution of rainfall in these stations. The data were analyzed using statistical package for social sciences, SPSS 17 and Minitab 16. The outcomes revealed that the maximum annual rainfall occurred at Warri station 4489.80 mm in the year 2008 and the minimum occurred at Benin 229.10 mm in 2005. Also, Benin has the maximum coefficient of variation of about 24.72%, while Port Harcourt has the minimum coefficient of variation of about 12.71%. Warri station was positively skewed indicating that it experienced frequent low rainfall values, while Port Harcourt was approximately symmetrical skewed. Warri has kurtosis coefficient of 4.45 which is highest among others. However, the patterns of rainfall in these areas are random or fluctuating. It is recommended that models built on the perceived decreasing rainfall, such as drainages, dams, have to be reviewed.