Future flood losses in major coastal cities

Journal name:
Nature Climate Change
Volume:
3,
Pages:
802–806
Year published:
DOI:
doi:10.1038/nclimate1979
Received
Accepted
Published online

Flood exposure is increasing in coastal cities1, 2 owing to growing populations and assets, the changing climate3, and subsidence4, 5, 6. Here we provide a quantification of present and future flood losses in the 136 largest coastal cities. Using a new database of urban protection and different assumptions on adaptation, we account for existing and future flood defences. Average global flood losses in 2005 are estimated to be approximately US$6billion per year, increasing to US$52billion by 2050 with projected socio-economic change alone. With climate change and subsidence, present protection will need to be upgraded to avoid unacceptable losses of US$1trillion or more per year. Even if adaptation investments maintain constant flood probability, subsidence and sea-level rise will increase global flood losses to US$60–63billion per year in 2050. To maintain present flood risk, adaptation will need to reduce flood probabilities below present values. In this case, the magnitude of losses when floods do occur would increase, often by more than 50%, making it critical to also prepare for larger disasters than we experience today. The analysis identifies the cities that seem most vulnerable to these trends, that is, where the largest increase in losses can be expected.

At a glance

Figures

  1. The 20 cities where the relative risk is larger in 2005, that is, where the ratio of AAL with respect to local GDP is the largest.
    Figure 1: The 20 cities where the relative risk is larger in 2005, that is, where the ratio of AAL with respect to local GDP is the largest.

    More information in Table 1.

  2. The 20 cities where AAL increase most (in relative terms in 2050 compared with 2005) in the case of optimistic sea-level rise, if adaptation only maintains present defence standards or flood probability (PD).
    Figure 2: The 20 cities where AAL increase most (in relative terms in 2050 compared with 2005) in the case of optimistic sea-level rise, if adaptation only maintains present defence standards or flood probability (PD).

    More information in Supplementary Table S7.

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Author information

Affiliations

  1. The World Bank, Sustainable Development Network, Washington DC 20433, USA

    • Stephane Hallegatte
  2. Centre International de Recherche sur l’Environnement et le Développement (CIRED), Nogent-sur-Marne 94736, France

    • Stephane Hallegatte
  3. Flood Hazard Research Centre, Middlesex University, London NW4 4BT, UK

    • Colin Green
  4. Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK

    • Robert J. Nicholls
  5. Organisation for Economic Co-operation and Development, Paris 75775, France

    • Jan Corfee-Morlot

Contributions

The four authors designed the study, interpreted results and authored the paper. S.H. developed and ran the models. R.N. and C.G. provided expert input on depth–damage curves and coastal protection.

Competing financial interests

The authors declare no competing financial interests.

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