Agizew, Nigussie (PhD)Wondimu, Paulos2021-02-232023-11-112021-02-232023-11-112020-09http://etd.aau.edu.et/handle/12345678/25193Overflow of water from existing drainage is emerging issue in many cities of Ethiopia and mainly in Addis Ababa. Unplanned growth of urban areas is affecting the urban drainage system in Addis Ababa. The drainage networks in the city do not have sufficient capacity to carry excess runoff due to rapid expansion of built in environment. The roads turning into streams can be easily observed in all parts of the city, especially in Megenagna to Bole Ring Road, during rainy seasons. The purpose of this study was to estimate peak flow rate due to expanding built environment in the study area using SWMM and propose measures that reduce excess stormwater or excess runoff by using generic LID Controls. Stormwater Management Model (SWMM 5.1) was applied to simulate the urban runoff from the Bole Gerji delineated area (about 188 hectares) located in Addis Ababa, Ethiopia in conjunction with other software’s like ArcGIS, Google Erath Pro, Excel and so on to analyze the quantitative data. Model calibration and validation process was conducted by using daily observed and simulated runoff at selected outlet near Anbesa Garage. Model calibration and validation at selected outlet gives coefficient of determination (R2) and Nash-Sutcliffe simulation efficiency (NSE) values of 0.91 and 0.86 and 0.95 and 0.88 respectively. This result indicated good agreement between observed values simulated runoffs. Built up area coverage changes from 14% to 94% in the last 25 years, and no substantial rainfall intensity variation was observed. Runoff generated from all sub catchments changed from 4.27 m3/sec in the past (1995) to 12.94 m3/sec in the present (2019). Conduits C1, C2, C3, C4, C5, C6, C11, C12, C17, C18 and C24 were under surcharge situation and Nodes J3, J5, J17, J18 and J24 on the main road (Megenagna - Bole) were found to be flooding or overflowing with total volume of 11.4*106, 28.5*106, 7.6*106, 12.1*106, and 12.4*106 liters respectively. Evaluation of performances of the proposed low impact development measures indicated positive results. Changing 3.6 ha paved pedestrian by permeable pavement (Scenario 1) reduced total runoff by 12% and total node flooding by 11%; and changing 1.6 ha paved pedestrian by Bio – Retention Cells (Scenario 2) reduced total runoff by 5% and total node flooding by 4%. Based on the thesis result scenario 1 was recommended. Before, the urban drainage becomes a permanent socio-economic nuisance and brings irreversible damage to the city, this study strongly recommends immediate implementation of Low Impact Development Controls (LID) that are supported by strong institutional setup, policy framework, and the public at large.en-USLand Use ChangeUrban DrainageSWMM 5.1LID ControlsThesis