PERFORMANCE ASSESSMENT OF STORM DRAINAGE SYSTEM, THE CASE OF WELKITE TOWN ,CENTRAL ETHIOPIA REGION,ETHIOPIA

Abstract

Most storm water drainage problems investigated with respect to its hydraulic performance.In Wolikite town drainage structures are not well-designed to carryout the runoff due to blockage & capacity on size of the ditch.The objective of this study is ,to assess storm water drainage system performance of the town. The study employed both primary and secondary data collection. To achieve the specific objective HEC-RAS model analysiss has been used to calculate peak discharge and the averge rainfall using log pearson type III, in order to develop the Intensity Duration Frequency (IDF) curve for the rainfall intensities recorded in different duration and analyzed for a period of 1991-2021. Detail evaluation of drainage channels is required to control damages on high storm. For sizing of existing and proposed drainage channels manning formula is used and the hydrological peak flow was determined by using Rational Method. It was found the discharge using rational method is that 1.78mcu , and the result from the HEC RAS model 0.08mcu compared with existing hydraulic capacity of the channels . It shows that study area storm water was higher with respect to the drainage channels to carry the expected runoff during high rainfall events, make incapable to carry the runnoff for drainage ditches of the study area. To resolve these problems BMP’s have been recommended and finally, the analysis from this study permits future work on re design of the town storm drainage ditches and resettlement of flood affected areas and amend land use of the town for residential should be considerd in connection with town master plan development