Investigation of Urban Drainage in Addis Ababa, the Case of Addis Ketema Sub City
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Date
2025-12-01
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Addis Ababa University
Abstract
Urban areas often face storm water management issues because the impermeable surfaces of roads, buildings and pavements do not allow for infiltration and lead to increased volumes of runoff and flooding. Cities in Ethiopia experience intense seasonal rainfall such as Addis Ababa. Addis Ketema sub city us particularly prone to flooding during the rain moths.
This research investigates the significant causes of flooding and assesses peak runoff for multiple sub-catchments in various return periods. By applying storm water management model, it also assesses the existing drainage system performance under varied runoff conditions. Hydrological study, filed survey and questionnaire were used to gather the required data. The
study utilized software and L-moment methods to choose an appropriate probability distribution that would help determine runoff with a return period of 2, 5, 10, and 25 years. Further analysis
consisted of IDF curves preparation, geospatial mapping with Google earth pro and hydrologic model. The study indicates that the primary causes of flooding are sediment build-up, lack of proper maintenance of drainage facilities, and widely spaced or blocked inlets as well as under sized drainage pipes. .Runoff during 2, 5, 10, and 25 years return periods was majorly traced from
sub catchments such as Awtobis Tera, ZZZ Foreign Employments, Addis Ketema Young Center and other vulnerable points. These areas produce a significant amount of runoff at junctions and
conduits of drainage systems. Simulation storm water management models should incorporate low impact development interventions including green roofs, permeable pavements and bio-retention cells as per the study recommendation based on the result. The updated model outputs show that low impact development measures reduce peak discharge and flooding, which supported by comparative hydrographs and tabulated results. The hydrologic and hydraulic components of the model were calibrated and validated using observed rainfall and flow measurements. Performance metric show strong reliability, including Nash-Sutcliffe value of0.74 during calibration and 0.86 during validation and coefficient of determination (R2
) values of 0.55 and 0.94 respectively. Overall, these results confirm that the model provides dependable predictions for storm water behavior within the study area.
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Keywords
Urban flood management, urban drainage, Storm water model management, Low impact development, Return period