Media release

From: Springer Nature

Climate science: Global increase of human settlements in flood-prone areas

Human settlements in flood zones increased by up to 122% between 1985 and 2015, according to a study published in Nature. The findings provide a comprehensive overview of the trends in global and regional exposure to flood hazards, accounting for local urbanization pattern and spatial development.

The growth of urban settlements has the potential to drive economic development, but also raises concerns about increased vulnerability to natural hazards and strains on public services and infrastructure. Although previous research has found that the populations affected by floods are growing, a systematic analysis of global flood exposure trends remains challenging due to the lack of high-resolution flood maps and human settlement data.

Jun Rentschler and colleagues combined global flood hazard datasets with annual high-resolution settlement footprint data from 1985 to 2015. They found that during this period, human settlements expanded by 85.4%. Settlements with the highest flood hazard exposure (that is, areas at risk of flooding depths of more than 150 cm during 1-in-100-year flood events) have increased by 122%, indicating that human expansion in high-hazard flood zones is faster than growth in areas with low risks of flooding. Flood exposure dynamics also differ across regions and countries in different income groups. The East Asia and Pacific region had the largest proportion of settlements in the highest flood hazard areas. Among all income groups, upper-middle-income countries hosted the largest proportion (60.8%) of settlements in highest flood hazard zones, and China is one of the main drivers for the substantial increase in flood exposure in this group. 

The findings reflect an important global trend and provide insights to urban planners and policymakers, especially given that extreme weather events are happening more often due to climate change.

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