Enhancing urban flood resilience in Nairobi using the Sponge City Concept
Urban flooding has become a persistent issue in Kenya posing a significant threat to the development, sustainability and liveability of its rapidly expanding cities. These flood events often result from intense rainfall events that overwhelm the capacity of drainage infrastructure and systems. The situation is further compounded by urbanisation, which introduces more impermeable urban surfaces, inadequate urban planning and the effects of anthropogenic climate change. Nairobi, the capital city of Kenya, has faced major incidences of flooding in recent years often disproportionately affecting the urban poor who reside in informal settlements that are less equipped to manage flood risks.
This research aimed to assess the potential of the Sponge City Concept as a viable intervention to enhance urban flood resilience in these regions. Sponge cities, a concept that has gained prominence in China, refer to urban areas designed to effectively manage and mitigate flood risks through nature-based solutions. This concept and other nature-based solutions have predominantly focused on adoption in Europe, North America and Australia. This paper aimed to examine a case study in the global south. Through desk-based research, application of remote sensing and Geographical Information Systems (GIS) technologies and semi-structured stakeholder interviews, this research explores the applicability of the Sponge City Concept for the case of Nairobi.
The findings of this structured assessment identify several key land use changes, with urbanisation the city’s built-up area is quickly increasing meaning increased surface runoff due to impermeable surfaces and the city is losing its vegetation cover leading to less runoff infiltration. It was also evident from the flood extent maps that the downstream population and populations in informal settlements are often the most affected by flooding events. The suitability mapping that followed revealed that Nairobi has greater potential to implement the Sponge City Concept to facilitate it in retaining, relieving and resisting rainwater to alleviate floods and increase the share of the resource in the region through recharge. The study recognised the need for great stakeholder engagement and involvement for the successful implementation of the Sponge City Projects.