Environment: 1.81 billion people at risk of 1-in-100 year flood

1.81 billion people may be exposed to inundation depths greater than 0.15 metres in the event of a 1-in-100 year flood, with the majority residing in South and East Asia, suggests a study published in Nature Communications. The research also reveals that 780 million people living on under US$5.50 a day are at risk from these floods and may have implications for targeted mitigation measures and policy.

Flooding is one of the most prevalent natural hazards and its impacts can be particularly acute for lower-income countries. While heightened flood risk is already a reality for many parts of the world, climate models have indicated flooding frequency could increase substantially in Africa, Asia and Latin America, which poses a risk for socioeconomic development. Although flood exposure assessments have been done at the local and national levels, a lack of global assessments limits our understanding of the impacts for lower-income countries and subregions.

Jun Rentschler and colleagues present results from a high-resolution global exposure assessment for 188 countries, using flood data from terrain and hydrographic models, and population maps to assess population exposure to flood risk. They combined this with poverty estimates from the World Bank’s Global Subnational Atlas of Poverty. The authors found that 23% of the world’s population (1.81 billion people) may be exposed to inundation depths greater than 0.15 metres in the event of 1-in-100 year floods (floods with a 1% chance of occurring in a given year), with the majority living in South and East Asia. They suggest China and India account for over one third of the global exposure. The study also finds that 89% of those facing flood exposure reside in low- and middle-income countries. The authors show that over 780 million people living on under US$5.50 per day face high flood risk, highlighting the relationship between flood exposure and poverty.