THE EFFECT OF CLIMATE CHANGE ON URAN DRAINGE: CASE OF BISHOFTU CITY DRAINAGE

Abstract

Climate change is a reality that planners and designers of drainage infrastructures must consider. Therefore, the risk should be investigated and quantified properly. The objective of this thesis is to investigate the effect of climate change on Urban Drainage having the case of Bishoftu city drainage. Projection of the future climate is done by using CMIP5 climate model outputs of RCP4.5 and RCP8.5 scenarios and downscaled daily rainfall and temperature data of CMIP5. The future climate projection analysis was done by partitioning the coming 50 years in two periods which are (2020-2040) and (2051-2070) and the 1994-2013 is taken as the base line period. These climate scenarios data were bias corrected for serving as input to the SCS for impact analysis. Using Easy fit software, the rain fall data was fitted to Gumball distribution for the quantile estimation. The quantile estimation of 2, 5, 10, 25, 50 and 100 years return period for the site were found to be 47.818, 60.043, 68.137, 78.363, 85.95, 93.481, 110.884 and 118.365. Respectively. The study area which are Kalhiwet church area and the market area water shed area of the drainage design was done. The hydrologic analysis of rain fall run off is computed by using modified SCS method and the hydraulics parameter is computed by 4.2 Hydraulic tool box software for the two catchment area with RCP4.5 and RCP 8.5 Scenarios of the two time horizon of 2030s and 2060s. Finally the design discharge amount is change in Market area by RCP 4.5 in 2060 is change by 63.3% and Minimum 18.64% in RCP 4.5Average design discharge, channel width and depth will increase up to 60.8% Max and 16.9% Min , 29.9% Max and 6.05% Min, and 20.21% Max and 6.7% Min depth is changed in KHC respectively. And for the design discharge of market area Max 63.3% and Min 18.64%, the width of channel is changed by 31.16% Max and 8.17% Min, and also the depth of the channel 32.22% Max and 9.09% Min also change. Therefore, the consideration of climate change on drainage is important