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coastal zones

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

Stéphane Hallegatte's picture

 NOAA via Wikimedia
The flooding of New Orleans, caused by Hurricane Katrina in 2005, illustrates the vulnerability of cities that are highly dependent on coastal defenses. Photo: NOAA [http://commons.wikimedia.org/wiki/File:Katrina-new-orleans-flooding3-2005.jpg]

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 US$1 trillion dollars.

What can be done?

Our analysis suggests that upgrading defenses could mitigate these losses and the impacts of rising sea levels. However, these upgrades need to include a package of risk management policies. First, coastal defenses should make use of the protection the environment can offer for free: Marshes, seagrass beds, coastal and kelp forests, and coral reefs provide natural buffers that absorb the energy from waves and storms, making it easier and cheaper to protect urban development. In addition artificial constructions are also required to provide full protection. We are not only talking about dykes: a city surrounded by dykes will need pumping systems to drain rainfall water, and a harbor will need moving barriers to let ships in and out of the port.

Water: A source of death and life

Jaehyang So's picture

With the recent MDG summit in New York, I think it’s a good time to stop and take a look at the big water and sanitation picture. We know the numbers of people without access are daunting: 2.5 billion with no sanitation, 887 million without access to safe water. But more and more people are indeed gaining access. Since 1990, 1.6 billion have gained access to safe water. The world will likely even reach the Millennium Development Goal (MDG) set in 2015 to halve the number of people without access to clean water, according to the UN.

This is no small feat, and the world should take a moment to celebrate this success, and learn from challenges encountered along the way so that we continue beyond 2015 until everyone can access clean water and sanitation.

Short video clip on the impact of a nickel mine in Tanjung Buli, Indonesia

Tony Whitten's picture

On the trip back to the base of PT Weda Bay Nickel after our two days in the Aketajawe-Lolobata National Park, we flew over the operating nickel mine at Tanjung Buli owned by publicly listed PT Aneka Tambang, but which has been operated since the opening in 2001 by a subcontractor.