The cost from global flood losses in coastal cities is projected to reach at least US$1 trillion annually by 2050 under current protection standards, reports research published this week in Nature Climate Change. With investments in adaptation, the annual costs in 2050 would still be significant, but lower at US$60-63 billion, the study shows.
The increasing magnitude of economic costs from flooding in coastal cities is explained by projections of climate change, subsidence, and growing populations and assets. Stephane Hallegatte and colleagues quantified such losses by looking at data from 136 of the largest coastal urban agglomerations around the world. They found that socio-economic changes alone raise the cost of damages from an estimated annual value of US$6 billion in 2005 to US$52 billion in 2050. Adding sea-level rise and subsidence to the analysis increases losses even if barriers - dykes, for example - are upgraded.
The authors highlight that 43% of these costs are incurred in only four cities - Miami, New York, and New Orleans in the US, and Guangzhou in China - and that the US has the largest number of highly exposed urban areas. Although current protection levels need to be upgraded, the study finds that infrastructure-based adaptation alone will not bring damages to an acceptable level; policies should therefore also focus on disaster planning and more comprehensive insurance schemes.