Assessing the Resilience of Sanitation Systems to Extreme Rainfall and Flooding

Climate change is exacerbating extreme weather events, such as heavy rainfall and flooding, posing major challenges for sanitation infrastructure. When sanitation systems fail in these conditions, they discharge fecal waste into the environment, heightening public health risks. However, key knowledge gaps persist. There is limited understanding of how sanitation systems respond to extreme rainfall and flooding and what drives infrastructure failure. While infrastructure failures are widely acknowledged, empirical evidence across diverse contexts is scarce. Moreover, few studies have directly linked these failures to environmental fecal contamination. This dissertation examines prior research and analyzes primary and secondary data to assess sanitation resilience in various contexts. Chapter 2 presents a systematic review of 162 studies from 46 countries, identifying sanitation system vulnerabilities, drivers of sanitation resilience, adaptation strategies, and evaluating existing assessment frameworks. Findings show pit latrines and septic systems are least resilient to flooding, often suffering structural damage, overflows, and service disruptions. Strategies such as elevating latrines, enforcing desludging, installing shut-off valves, and promoting community-led flood responses can mitigate impacts. Current sanitation resilience frameworks are scarce, inconsistent, and yield variable results. Building on these insights, Chapter 3 develops and applies a novel sanitation resilience assessment framework in 200 shared facilities in Kibera, Kenya. Results highlight the interplay of infrastructure design, operations, and environmental factors in determining resilience. Chapter 4 applies a Bayesian Belief Network to analyze 18,534 onsite sanitation systems across 14 LMICs, identifying desludging history and skilled maintenance as key predictors of functionality, with flooding exacerbating failures. Chapter 5 details a field study conducted in Nairobi, where 200 soil and drain samples were tested for fecal contamination, and a dye tracer was used to track waste flows from failing sanitation systems. We detected E. coli in 78% of the samples, with concentrations varying based on sanitation infrastructure and household characteristics. Contamination generally decreased following rainfall (p = 0.097). Tracer dye was found in 56% of samples, rising to 78% after rainfall events, suggesting that the sanitation technologies we studied do not effectively contain waste and offer limited protection to public health. This research advances understanding of sanitation resilience to extreme weather in low-income settings, offering practical insights for policymakers, practitioners, and communities to strengthen infrastructure resilience and safeguard public health.