Author(s): Seith N. Mugume; Hilary Kibibi; Milton Wakhata

Linked Author(s): Seith Mugume

Keywords: Flooding; Blue-green infrastructure; Climate change; Drainage

Abstract: Globally, climate change and urbanization have exacerbated the occurrence of catastrophic flooding impacts and consequences. In Kampala, Uganda, urban flooding affects over 170,000 people, with the annual flood damage to buildings estimated at US$49.6 million in 2021. Enhancing the resilience of urban drainage systems (UDSs) is vital to maintain acceptable levels of system functionality during extreme rainfall events. Reliabilitybased approaches focusing on expanding conventional grey infrastructure have proven ineffective due to increased extreme rainfall, inadequate maintenance, and solid waste deposition. Although blue-green infrastructure solutions have been proposed, adoption at the city scale is low. This study evaluates the effectiveness of blue-green infrastructure options in enhancing the resilience of the Nalukolongo Drainage System, which frequently floods. Catchment delineation, determination of key sub-catchment parameters was undertaken using GiS-based spatial analysis. Furthermore, extreme rainfall frequency analysis was undertaken to determine design rain storms with higher returns and with consideration of climate change impacts. The existing drainage system and blue-green infrastructure (BGI) options that included rainwater harvesting tanks, bioretention cells, infiltration trenches and detention ponds were modelled in PCSWMM, a 1D-2D physically based model. Multiple simulations were undertaken to assess the effectiveness of the proposed BGI options in reducing flooding, considering non-failed and failed UDS initial states. The study results suggest that spatially distributed rainwater harvesting systems and infiltration trenches led to over 43% reduction of resulting flooding impacts. Therefore, wide scale implementation of such systems at a city scale could provide promising urban flood resilience strategies in rapidly urbanizing cities in sub-Saharan Africa.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0876-cd

Year: 2023