Miami is projected to have the world's highest coastal flood risk by the 2070s, with property and infrastructure exposed assets increasing from $400 billion today to more than $3.5 trillion, according to a new study.
The findings, part of an international outlook for coastal flooding, were in a report by the Paris-based Organisation for Economic Co-operation and Development and jointly authored by Newark, Calif.-based Risk Management Solutions (RMS) modeling group and academic groups.
According to the study, as a result of climate change and urban development, up to 150 million people in the world's major cities could be reliant on flood defenses by 2070–more than three times the 40 million people today.
The study group included the UK's University of Southampton; Tyndall Centre in Norwich, UK; M?t?o-France, Paris; and the Centre International de Recherche sur l'Environnement et le D?veloppement (CIRED), Nogent Sur Marne, France.
According to the group preparing the report, it is the first stage of the largest study on urban coastal flood exposure ever undertaken.
After Miami, the study said the next two cities with the highest flood risk are Guangzhou in China, with a $3.3 trillion exposure, and New York City, with a $2.1 trillion exposure.
Total property and infrastructure exposure worldwide is predicted to increase from $3 trillion today (5 percent of current global gross domestic product) to $35 trillion in the 2070s (9 percent of the projected global GDP).
The report said the findings highlight the opportunity and a necessity for the insurance industry to promote climate change adaptation measures.
Included in the study is an analysis of more than 130 key port cities worldwide that were looked at for how they would be impacted by climate change alongside subsidence, population growth and urban economic development.
The research with 2005 data focused on the exposure of people, property and infrastructure to a 1-in-100-year flood event now and in the future.
The top ten cities, which contain 60 percent of the total exposure, are from only three wealthy countries–the United States, Japan and The Netherlands, the report said.
Although Miami currently has the highest risk, the report found that rapid economic development expected in the nations under development means that in the future the highest exposure will become more concentrated in Asian cities, with eight of the top ten situated in this region.
After Miami, Guangzhou and New York, the report lists Kolkata, Shanghai, Mumbai, Tianjin (China), Tokyo, Hong Kong and Bangkok, respectively, for risk.
"These findings deliver a clear message to businesses that invest, or are planning to invest, in highly exposed cities to start implementing pro-active risk management strategies that consider how risks will evolve over time," said Celine Herweijer, principal scientist of future climate at RMS.
Ms. Herweijer said, "For the insurance industry, there is both an opportunity and a necessity to promote adaptation. Crucially, rising hazard does not have to translate into increased risk if the right measures are taken."
Looking ahead to the 2070s, the cities with the greatest population exposure were projected to rise most rapidly in developing countries, with nine of the top ten cities in Asia.
Kolkata (Calcutta) was seen as most vulnerable, with the exposed population expected to increase over seven times to more than 14 million people, largely driven by the rapid population growth of the city.
In terms of population exposure, Kolkata is closely followed by Mumbai, Dhaka, Guangzhou, Ho Chi Minh City, Shanghai, Bangkok and Rangoon (Myanmar). Miami is in ninth place and would be the only top ten city situated in a currently developed country, while Hai Phong (Vietnam) is ranked tenth.
"Population growth and development are clearly key drivers of the increase in exposure, particularly in Asia, but climate change and subsidence acutely magnify the problem," commented Ms. Herweijer.
"The concentration of flood exposure in rapidly developing cities urgently underscores the need to integrate climate change implications into both national coastal flood risk management and urban development strategies," said Robert Nicholls, IPCC author and director of research at the University of Southampton.
St?phane Hallegatte, economist at M?t?o-France and CIRED, said "adaptation strategies need to be underpinned by solid governance to help key cities understand and proactively manage current and future flood risk."
It was noted that putting effective disaster management strategies and protection investments into place will take time. Previous defense projects, like the Thames Barrier in the U.K., have demonstrated that implementing coastal protection infrastructure typically takes at least 30 years.
An executive summary of the report is online at www.rms.com.
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