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Increasing Flood Risks Create Major Challenges for World’s Coastal Cities

Stéphane Hallegatte's picture

Increasing flood risks create a major political and institutional challenge for the world’s coastal cities as ambitious and proactive action at the local level over the next decades will be needed to avoid large-scale flood disasters. However, the implementation of flood risk management policies meets many obstacles. 

In a recent study written with colleagues Colin Green, Robert Nicholls and Jan Corfee-Morlot as part of an OECD project on urban vulnerability, we estimate how flood risks could change in the future in 136 coastal cities, in response to increasing population and wealth, local environmental change, and climate change. We find that because current flood defenses and urbanization patterns have been designed for past environmental conditions, even a moderate change in sea level is sufficient to make them inadequate, thus magnifying flood losses to catastrophic levels. If no action is taken to reduce flood vulnerability, most coastal cities would become inhospitable and dangerous places to live, with annual losses in excess of $1 trillion dollars.