Abstract

Flooding caused by stormwater drainage systems is a key issue in urban development that is influenced by land use, climate change, and topography. Simulation models, such as the Stormwater Management Model, can be used to accurately estimate flood problems (SWMM). This study calculated the effect of topography on the Al-Ameer District. In addition, the impacts of climate change (2, 5, 10, and 25 years) with topography slope of 0.5% to 0.4%, 0.3%, 0.2%, and 0.1%, and concentration-time (downstream and upstream) on the stormwater drainage system were evaluated using SWMM simulation. The results showed, during the return period of 2 years and a slope changed from 0.5% to 0.1%, the flood decreased 44%. During the return period of 5 years and a slope changed from 0.5% to 0.1%,  the flood decreased 29%. During the return period of 10 and 25 years and a slope changed from 0.5% to 0.1%, the flood decreased 21%. A limited sub-catchment slope effect was inferred with a significant decrease in flooding, while a low sub-catchment slope had little effect on flooding in a return period of 10 and 25 years. Finally, the rise of the sub-catchment slope has resulted in a further increase in runoff, leading to flooding. The results also showed that the flood time occurs downstream before upstream, indicating that the downstream region suffers from topographic and design problems. This was demonstrated by flooding the manhole R315 before the manhole R15 because the slope of the sub-catchment in the opposite direction of the flow in the pipes, as well as the depth of the manhole, is shallow. In conclusion, as the locations and magnitude of the floods were determined, the system failed to drain rainwater in some critical conditions. Also, designers should match the sub-catchment with the slopes of the network tubes to reduce flooding.