Assessment of the impact of climate change on Urban Flood Risk In Kampala City using statistical downscaling and a coupled 1d-2d Model (A Case Study Of Nakivubo Channel).
Nakyanzi, Lydia Patricia
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Urban flooding is a significant challenge in Kampala causing economic disruptions, property damage, and threats to public health and safety. With climate change exacerbating the frequency and intensity of heavy rainfall events, the risk of flooding in the city is expected to increase. This study aims to model urban flooding in Kampala using a coupled 1D-2D model and assess the impact of climate change on flood risk. The research focuses on the Nakivubo channel, a crucial drainage system in the city, which frequently experiences blockages and overflows during heavy rain. The study utilizes the latest shared socioeconomic pathway scenarios SSP2-4.5 and SSP5-8.5 to project future climate change conditions and assess their influence on urban flooding. It also develops a coupled 1D-2D model, the PC SWMM model, to simulate flooding in the catchment and analyze the extent and depth of flooding. Additionally, the efficiency of blue-green and grey infrastructure solutions in enhancing the urban drainage system's resilience to climate change-induced flooding is evaluated. In the higher emission trajectory, the SSP5-8.5 CANESM5 scenario exhibited an increase of approximately 1,054.8% in total flood volume, indicating an elevated risk of large-scale flooding events. Despite decreases in average hours flooded (approximately 18.5% and 12.7% for SSP5-8.5 MIROC6 and SSP5-8.5 NORESM2-mm, respectively, these scenarios still experienced increased intensity of rainfall events leading to peak flows, reflected in increases in average maximum rate (approximately 66.4% and 67.5%) and total flood volume (approximately 111.2% and 91.5%). The implementation of blue-green infrastructure measures, specifically Rain barrels, Infiltration trenches, and Rain gardens, under the SSP5-8.5 CANESM5 scenario, proved effective in reducing flood risk compared to the baseline. The Rain barrels scenario showed a decrease in total flood volume by approximately 68.6%. Similarly, the Infiltration trenches scenario demonstrated reductions of 75.5% in total flood volume. The Rain gardens scenario also displayed reductions of 45.7% in total flood volume. With the challenges of limited technologies, monitoring infrastructure, and technical limitations in climate modeling, efforts to develop climate change-related information systems are crucial for Uganda's response to climate change. Ultimately, this research aims to contribute to the development of climate-adaptive and resilient infrastructure in Kampala and provide insights into sustainable urban drainage systems that can mitigate the adverse impacts of urban flooding in the face of climate change.