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Climate change poses growing flood risks to US coastal cities

<p>Millions of U.S. residents -- as well as commercial buildings, agriculture and more -- are at risk from rising sea levels and storm surges, new research from Climate Central finds.</p>

[Editor's Note: Today is World Water Day. In this article, Robert Kropp of SocialFunds discusses how rising sea levels and storm surges threaten commercial buildings, agriculture, nuclear plants and much more, and are already causing billions of dollars in insurance losses. Please also see the post by GreenOrder's Simon Lim on how energy companies manage their water footprints.]

Since 1880, average sea levels have increased by more than 8 inches, most if not all of which can be attributed to the impacts of climate change. According to Climate Central, in a report entitled Surging Seas, unchecked climate change is likely to make things much worse, and soon.

The study projects that sea levels could rise as much as an additional eight inches by 2030. Furthermore, "The rate of rise is accelerating," Climate Central reports. "Scientists expect 20 to 80 more inches this century."

One effect of rising sea levels is likely to be massive migration by populations in low-lying areas. The Center for International Earth Science Information Network has estimated that there could be as many as 700 million climate refugees by 2050. And CIESIN states, "Sea-level rise appears to be the impact most certain to result in displacement and resettlement."

"Migration may be the only adaptive response," the center continued. Cynthia McHale of Ceres recently reported on an extreme example of migratory adaptation, writing, "The president of Kiribati, a low lying nation of small South Pacific islands, announced that his country was buying 6,000 acres of land in Fiji because climate-driven sea level rise is threatening to submerge his country. The plan of last resort is to move the entire population of 103,000 to Fiji."

In case the U.S.-based reader is tempted to breathe a sigh of relief that the initial impacts will be felt at such a distance, it must be noted that the Surging Seas report focuses on impacts at home. Fifty-five sites within the U.S. were analyzed, and the report finds that three-quarters of them -- nearly 5 million people in 2.6 million homes -- live in areas lower than four feet above the high tide line; but average sea levels have already exceeded four feet. An additional 3.7 million people live less than one meter above the high tide line.

"The population and homes exposed are just part of the story," the report states. "Flooding to four feet would reach higher than a huge amount of dry land, covering some 3 million acres of roads, bridges, commercial buildings, military bases, agricultural lands, toxic waste dumps, schools, hospitals, and more."

To make matters even worse, Climate Central observes, "Rising seas dramatically increase the odds of damaging floods from storm surges." The likelihood of so-called "century floods" -- floods that are unlikely to appear more than once in a century -- is expected to double by 2030. In fact, at two-thirds of the locations analyzed by Climate Central, the annual risk of such floods has already doubled.

In New Jersey, the projected sea level rise is 15 inches by 2050, and the likelihood of century floods will have more than tripled by 2030.

Half the exposed population, as well as eight of the 10 most vulnerable cities, are located in Florida. The state is already experiencing flooding at extreme high tides and contamination of freshwater aquifers by the ocean. Because southern Florida uses manmade canals to handle storm runoff, 6 inches in sea level rise will cripple the system.

As McHale of Ceres notes, the Florida Climate Institute has estimated that sea levels in the state could increase by as much as 32 inches by 2100.

Climate Central projects that about $30 billion in taxable property located in just three counties in southeast Florida is vulnerable. The projection doesn't include Miami-Dade County, where more homes are at risk than in any other county in the nation.

The city with the largest population living on land less than four feet above local high tide is New Orleans.

In 2011, property and casualty insurance losses in the U.S. totaled $44 billion; and, as Pete Thomas, chief risk officer at Willis Re, said at a Capitol Hill press conference held earlier this month, "Demographics and coastal urbanization are catastrophic force multipliers making weather events increasingly more costly." Representatives from the reinsurance industry called on policymakers to enact legislation that meaningfully addresses the reality of climate change.

"A warming climate will only add to this trend of increasing losses, which is why action is needed now," said Mark Way, the head of Sustainable Development at Swiss Re.

To complicate worse-case scenarios even further, McHale writes, "With the Fukushima nuclear disaster fresh in mind, it's worth noting that more than a dozen U.S. nuclear power plants sit in low-lying coastal areas, too."

In the absence of meaningful action by legislators, Climate Central has documented a number of regional action plans addressing the effects of climate change on coastal areas. Texas Sea Grant, for example, made the following recommendations:

• Reform the National Flood Insurance Program by ending the practice of subsidizing insurance in hazardous areas;
• Government mandates for effective community plans that incorporate hazard mitigation planning;
• Strict adherence by vulnerable cities to state of the art building codes; and
• Reserving engineered solutions such as seawalls, levees, and dikes for "truly inevitable cities in impossible places," such as New Orleans.

"We are past the point where we can prevent climate change; the question now is how to mitigate the risks and the dire and predictable economic and social disruption that will inevitably follow," McHale of Ceres concluded. "The answer isn't a mystery: we need a rapid transition to a low-carbon economy. DC policymakers need to stop fiddling while the invisible tsunami builds just off our shores."

This article originally appeared in SocialFunds.

Aerial photo of Miami via

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