India’s financial capital and largest city, Mumbai, is facing increasing vulnerability to climate change-induced floods. A recent study found that extreme rainfall during the monsoon season, which lasts from June to September, contributes to about 8% of the coastal megacity’s deaths each year. Shockingly, 80% of the individuals who perish during flooding events, particularly during high tides, reside in the city’s vast slum areas.
The study, published in the journal Nature on November 12, 2025, sheds light on the disproportionate impact of heavy rainfall on different demographic groups. Children under the age of five face the highest mortality risk, followed by women, with men at a comparatively lower risk. The researchers discovered that a single day of 150mm of rainfall led to a 5.3% increase in five-week mortality among young children, a 1.6% increase among adults aged 5 to 64, and a 2.3% increase among individuals over 65 years old.
The rapid urbanization of Mumbai, coupled with inadequate infrastructure development, has exacerbated the city’s susceptibility to flooding. The study emphasizes the urgent need for improved drainage, sanitation, and waste management systems to mitigate the adverse health impacts of heavy rainfall. With over one billion people living in slums globally, the researchers highlight the heightened vulnerability of slum inhabitants to flooding hazards.
Furthermore, the researchers warn that future sea-level rise will intensify flooding risks, underscoring the critical importance of effective urban flood management strategies. Lead author Tom Bearpark and his team from Princeton University analyzed a decade of rainfall data and death records in Mumbai, uncovering the stark disparities in mortality rates between slum and non-slum populations.
The study concludes by advocating for investments in water, sanitation, and drainage systems to reduce urban mortality rates, particularly in slum areas. These investments have proven effective in lowering child mortality rates in developed countries and could yield similar benefits in developing urban areas. As cities in the developing world continue to expand, with a significant portion of growth occurring in slums, prioritizing infrastructure development is crucial to safeguarding public health and promoting sustainable urban development.
