London – December 4, 2007 – As many as 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 – as a result of climate change and urban development.  This is according to a major new study by the Organization for Economic Co-operation and Development (OECD) and jointly authored by Risk Management Solutions (RMS) and leading academics from the University of Southampton, the Tyndall Centre, Météo-France, and the Centre International de Recherche sur l’Environnement et le Développement (CIRED).

The findings are from the first stage of the largest study on urban coastal flood exposure ever undertaken. Over 130 key port cities worldwide are analyzed to investigate the likely impact of climate change alongside subsidence, population growth, and urban economic development. The study focuses on the exposure of people, property, and infrastructure to a 1-in-100 year flood event now and in the future, and could have significant public policy implications for where to focus adaptation strategies to climate extremes.

Property & Infrastructure Exposure

The cities with the highest value of property and infrastructure assets exposed to coastal flooding caused by storm surge and damage from high winds today are primarily in developed countries.  The top ten cities, which contain 60% of the total exposure, are from only three wealthy countries (U.S., Japan, and the Netherlands), with Miami ranked as top.

Miami remains at the top of the 2070 rankings, with exposed assets rising from approximately US$400 billion today to over US$3.5 trillion.  However, the rapid economic development expected in the nations under development means that in the future the highest exposure becomes more concentrated in Asian cities, with eight of the top ten situated in this region. Guangzhou is the second most exposed city in terms of assets, followed by New York, Kolkata, Shanghai, Mumbai, Tianjin (China), Tokyo, Hong Kong, and Bangkok, respectively.

“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 Dr. Celine Herweijer, principal scientist of future climate at RMS. “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.” 

She added: “Where risk is today privately insured, incentivizing adaptation among policy-holders will serve as a double pay-back for insurers. Likewise, as insurers and business expand their business in Asia, public and private investment in adaptation will be critical to sustaining long-term financial stability.”

Population Exposure

The study shows that around half of the total population exposure to coastal flooding caused by storm surge and damage from high winds is contained in just ten cities.  Today, the ten most exposed cities are fairly evenly split between developed and developing countries, with Mumbai having the highest exposure to coastal flood.

Looking ahead to the 2070s, exposure rises most rapidly in developing countries, with nine of the top ten cities in Asia.  Kolkata (Calcutta) is 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.  Over the coming decades, the unprecedented growth and development of the Asian mega-cities will be a key factor in driving the increase in coastal flood risk globally. 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 Dr. 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 Prof. Robert Nicholls, IPCC author and director of research at the University of Southampton.  “Given the aggregation of people and assets in port cities and their importance to global trade, failure to develop effective adaptation strategies would inevitably have not just local, but international economic consequences.”

The annual probability of a 1-in-100 year event affecting one major city globally is as high as 74% and almost 100% over five years. “Even being optimistic that flood protection levels will be high everywhere in the future, the large population and asset exposure is likely to translate into regular city-scale disasters across the globe,” said Stéphane Hallegatte, economist at Météo-France and CIRED. “Adaptation strategies need to be underpinned by solid governance, to help key cities understand and proactively manage current and future flood risk.”

“This report raises crucial policy considerations, and highlights the urgency for climate change mitigation, and risk-informed adaptation strategies at a city level,” said Jan Corfee-Morlot, senior policy advisor on climate change at the OECD.  “Mitigation will slow and limit the exacerbating effects of climate change on coastal flood risk, at a minimum bringing precious time for cities to implement adaptation measures.” 

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.

This report, "Ranking of the World's Cities Most Exposed to Coastal Flooding Today and in the Future, " is part of a series planned by the OECD on the theme of Cities and Climate Change.   Further work will look at the effectiveness of flood defense measures and the vulnerability of key cities globally. 

On December 10, Dr. Herweijer will present the results of the study at the United Nations Framework Convention on Climate Change.

Read Executive Summary of "Ranking of the World's Cities Most Exposed to Coastal Flooding Today and in the Future"

OECD
The Organization for Economic Co-operation and Development (OECD) is an intergovernmental organization, representing 30 member countries, all of whom are committed to common principles to support economic development, including among others, protection of environment and social protection.

CIRED
The Centre International de Rercheche sur l’Environnement et le Développement (CIRED) is a laboratory in economics that studies the interactions between environment, climate change, natural disasters, long-term natural resource management, and economic development.

Tyndall Centre
The U.K.’s Tyndall Centre for Climate Change Research was founded in 2000 and is the UK’s leading scientific research centre for undertaking integrated research that contributes to the development, evaluation and promotion of sustainable options for responding effectively to climate change.

University of Southampton
School of Civil Engineering and the Environment
The University of Southampton is one of the top 10 research universities in the U.K. and has achieved consistently high scores for its teaching and learning activities. Currently it has nearly 20,000 students and 5,000 staff. Its discipline base is broad, encompassing all the major academic subjects, but it also has a unique commitment to innovation, evidenced both in its outstanding research and scholarship at the leading edge, and its ability to pioneer new approaches and techniques.