Flood Frequency Analysis of River Kaduna, Kaduna State, Nigeria, using Precipitation Concentration Index

Authors: Butu AW, Leke DC, Emeribe CN, Jibril MS

DOI Info: N/A

ABSTRACT

Flood frequency analyses of River Kaduna using the precipitation concentration index model, (PCI) was investigated. Rainfall data was collected for the duration 1962-2015 while stream discharge data at the Kaduna South gauging station was collected from 1967 to 2000. Precipitation concentration was classified based on the transformed annual precipitation departure (TAPD) and precipitation concentration index (PCI). Hydro-climatic data were analyzed for trends, fluctuations, exceedance probability, cumulative, lognormal and return periods for extreme values. Precipitation concentration index from 1962 to 2015 revealed that precipitation concentration was dominantly irregular and strongly irregular. The transformed annual precipitation departure showed that 16 years out of 54 years rainfall time series were wet years and these coincided with the flood events of 2003 and 2012. The PCI also showed that 19 years had strong irregularity of precipitation distribution meaning that for 19 years, precipitation concentrated in 4 months of each year, most of which coincided with years of drought in the Sudano-Sahel region of Nigeria. The calculated return periods for the 25 flood years revealed that the highest rainfall volume was recorded in the year 2013 with a return period of 55 years, while the lowest amount was in 1999 with a return period of 2.2 years. Due to the strong relationship observed in the regression analysis, it can be concluded that flood events coincided with periods of rainfall surpluses thus making PCI an effective model for flood prediction.

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