PERFORMANCE ASSESSMENT OF URBAN DRAINAGE SYSTEMS OF ALETA-CHUKO TOWN

Abstract

As the process of urbanization accelerates, drains become increasingly overloaded and unable to cope with heavy rainfall. The main objective of this study was to assess the performance of the urban drainage system in Aleta-Chuko Town. Both primary and secondary data were collected by field survey, Resident community, agency, Municipal administration, books, and articles. Rainfall data were used from Ethiopian Meteorology Agency from 1991 to 2019 (30 years) data. To develop the Intensity Duration Frequency curve (IDF) the rainfall intensities for the different duration were selected as the best-fit probability distribution based on Easyfit professional 5.6 software and correlation coefficient. From the analysis result, log-Pearson Type III was the best fit probability distribution for this study area as confirmed goodness of fit tests statistics for different return periods. Considering the current land use, rainfall intensity, and catchment area, the peak discharge was estimated using the rational formula. The adequacy of the existing drainage systems were checked by comparing the estimated runoff with the existing drainage capacity . The Stormwater Management Model (SWMM 5.1) was applied to simulate the water level in the links and junctions by considering the current land use condition.The model allows the catchment area to be subdivided into sub-catchments. For this study area is subdivided into 32 sub-catchments. From model simulation result’s a number of the existing drainage lines are undersized, and therefore not able to handle the required capacity of a 10-year storm occurrence. Typical flooding during the rainy season sub-catchments are: S-C-02, S-C-03, S-C- 13, S-C-14, S-C-27, S-C-28, S-C-30, and S-C-31. The storm overtops the drainage system. In another hand, some stormwater drainage systems were oversized. Based on the GTZ standard, For instance total drains about 37.93% is severely degraded, and 24.2% is light around existing market and Aleta- Chuko Primary Hospital. Finally, lack of community awareness, drainage systems are not well connected,and improper construction alignment problem for the existing system were investigated, and to avoid this problem creating awareness for the community, repair degraided channel either fully or partially, providing drainage channels without drainage system’s, periodic cleaning and modification of slope is recommended