PERFORMANCE EVALUATION OF KEWADO TOWN, DRAINAGE SYSTEM IN SIDAMA REGIONAL STATE

Abstract

Developing countries experience accelerated urbanization without adequate investment in infrastructure. kewado town, like other towns of Ethiopia, have a lot of problems including inadequacy and poor-quality drainage infrastructure. This study was aimed to assess the Performance Evaluation of Kewado town Drainage Systems focused on the western and eastern part of the main road of the town. Both field and historical climatic data were collected and analyzed. Rainfall data for a period of 1990-2019 were used for the study. The methodology employed in this study starts with identifying parent probability distribution for the rainfall intensities with various return periods. This enabled to develop the Intensity Duration Frequency Curve (IDF). The rainfall frequency analyses depicted thatthe log-Pearson III distribution best fits the rainfall intensities as confirmed by the goodness of fit tests. . Rainfall quintiles for a duration of 24hr with a magnitude of 52.4, 62.9, 75.6, 86.9, 95.1 and 103.3 mm/hr. was predicted fora return period of 2,5,10,25, 50 and 100 years respectively The hydraulic dimensions of existing structures were measured in the field using tape meter. The catchmentthat contributes runoff areas, weighted runoff coefficient was delineated using Arc GIS 10.7 tool. Considering the current land use, rainfall intensity and catchment area, the peak discharge was estimated using the rational methods. The Manning equation was used for fixing the dimensions of the storm drainage canals. The adequacy of the existing drainage systems were checked by comparing the estimated runoff with the existing drainage capacity. Hence, most of drainage lines were inadequate to safely dispose of the runoff. Based on the GTZ standard, 60 %, 46 %, 18% and 48% of the existing canals were performed with the severe and light conditions around Mazegaja, Ethiotele, TVT college and Darancho respectively.Illegal disposal of solid & liquid waste into drainage systems, lack of sewer line, unavailability of drainage for some part of town, low community awareness, low mitigation measures and dis- connectivity of drainage were the major problems.. The Stormwater Management Model (SWMM 5.2) was applied to simulate the water levelin the links and junctions by considering the current land use condition