Flood-risk vulnerabilities of sanitation facilities in urban informal settlements: Lessons from Kisumu City, Kenya

Abstract

Flood disasters have increased in frequency and severity over the recent decades causing untold destruction to vulnerable physical infrastructure such as sanitation facilities. Factors including construction quality, design, siting, and users’ behaviour further exacerbate the vulnerability of facilities. Despite this reality, very little has been done to document the extent of flood risk facing such facilities in the pro-poor urban informal settlements in developing countries. This study assessed the flood risks of vulnerable sanitation facilities in the urban informal settlements of Kisumu city, Kenya. The methodology involved assessment of sanitation facilities’ flood vulnerabilities and assessment of flood risk models. Flood risk was assessed by estimating runoff from yearly rainfall totals and also by calculating storm return period and probability of exceedance. Vulnerability assessment for each sanitation facility was done by scoring against flood risk indicators ordered by weighted rank. The study observed that majority sanitation facilities in the urban informal settlements were considered “highly vulnerable” (57%). Flood risk analysis predicted growing vulnerability due to shorter storm return periods, especially under the RCP 8.5 scenario. It was established that over 20% of all rainfall events in the 50-year timeline had higher than 80% probability of exceedance rainfall, signifying higher storm risks. Additionally, the study showed that between 44% of rainfall received in the study area could translate to runoff, in the near future, further compounding flood risk predictions. With key informal settlements such as Nyalenda and Manyatta facing stronger future flood risks, general public health may be threatened, leading to increased social and economic instability on families and households. The study recommends adherence to improved toilet standards of construction and toilet-raising as methods of improving flood risk resilience and adaptation.