FLOOD RISK ANALYSIS IN BORA WOREDA GORA FLOODPLAIN UPPER AWASH RIVER BASIN, ETHIOPIA

Abstract

Flood is a natural disaster and it causes loss of crop production as well as loss of life and property for people who are living around the floodplain. The Upper Awash River and flooding continue to be inseparable for long time in. The aim of this study was to investigate flood risk at different return period with respect to crop failure in the Gora flood plain Awash River Basin. The stream flow data from 1975 to 2015 at Hombole station was used to compute the flood peaks for various return periods. The Easy fit tool 5.5 version was used to compute the parameters of probability distribution which best fit the time series data. The HEC GeoRAS and HEC RAS models were used to reprocessing the input data, delineating the flood extent for various return period and flood modeling, respectively. The results of the frequency analysis indicate that the extreme value type I distribution best fitted the data. It was found that a peak discharge of 429, 527, 628, 676, 695 and 716m3/sec for 2, 5, 25,100,200 and 500 year return period respectively. These flood peaks in turn inundating agricultural area of 3212, 3292, 3359, 3391, 3403 and 3414hectares for 2,5,25,100,200 and 500 year return period respectively. The flood risks were estimated based on the percentage of the crop coverage and crop yield per hectare. Based on the analysis 75288, 77163, 78755, 79503, 79784 and 80028 quintals were lost for 2,5,25,100,200 and 500 year return period respectively.