Unmanaged rainfall is an escalating public health threat for cities worldwide. Nearly 1.8 billion people live in flood-prone areas. This number is rising rapidly as urbanization expands into risky zones and climate change intensifies rainfall. In many parts of the Global South, drainage, sanitation, and waste systems have not kept pace. This has been turning heavy rain into hazards that cause both immediate deaths and longer-term disease outbreaks. Future sea level rise will further amplify flooding hazards making rainwater and urban flood management a defining challenge of 21st century public health, economic development, and urban planning policy.
EPIC researcher Ashwin Rode and his co-authors study the impact of rainfall on mortality in one of the world’s largest cities—Mumbai, India. They find that rainfall accounts for about 8 percent of deaths during a typical monsoon season—a number comparable with cancer deaths in the city. The impact of this rainfall takes a heavier toll on poor residents, who live in areas of the city called slums. Slum residents account for 85 percent of the deaths from rainfall. Rainfall deaths make up 11 percent of the deaths of slum residents during a monsoon season, but only 2.4 percent of deaths of those living outside of slum areas. Woman and children are also more impacted by heavy rainfall, with rainfall making up 18 percent of deaths for children under 5—reflecting their vulnerability to waterborne diseases like diarrhea—and 11 percent of deaths for women.
The study also finds that intense bursts of rain, and especially intense bursts of rain combined with high tides, are the deadliest—largely due to inadequate drainage that leads to heavy flooding that often lingers. As the climate warms, its projected rainfall will intensify and sea levels will rise—amplifying these already deadly impacts. The study finds rainfall deaths will increase by as much as 20 percent over the coming decade if steps aren’t taken to adapt.