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Posted at 11:28 AM ET, 03/14/2012

Sea level rise from global warming magnifies coastal flood risk in Washington, D.C., mid-Atlantic


Odds of extreme coastal floods in Washington, D.C., Virginia, and Maryland by 2030 with sea level rise from global warming and without (ClimateCentral.org)
Sea level rise resulting from global warming will dramatically increase the risk of storm surge flooding in Washington, D.C. and along much of the U.S. coast, according to a new report from Climate Central, a non-profit science research and communication group. Its report, “Surging Seas” describes the risk of exceeding established flood levels by 2030, when taking projected sea level rise into account.

Here are some key findings from the report, specific to the mid-Atlantic region:

* Along the shores of Maryland, sea level rise (from global warming) multiplies the risk of a 100-year flood (or worse) by 2030 1.8 times, from 12 percent to 22 percent.

* Along the shores of Virginia, sea level rise multiplies the risk of a 100-year flood by 2030 by more than a factor of three, from 9 percent to 29 percent.

* Along the shores of Delaware, sea level rise multiplies the risk of a 100-year flood by 2030 by more than a factor of three, from 6 percent to 33 percent.

* Along the shores of the tidal Potomac in Washington, D.C., sea level rise increases the risk of a 100-year flood by 2030 from 16% to 19%.

Detailed projections for specific water level stations are provided in the report.

The report also estimates the land, housing, and population vulnerable to storm surge flooding in low-lying areas in all of these areas.

Here are some of its findings for the mid-Atlantic:

* In Maryland, storm surge flooding threatens 53,000 people, 40,000 homes, and 257,000 acres of land in the coastal zone at an elevation below 5 feet. The three cities with most exposed population? Ocean City, Ocean Pines, and Crisfield.

* In Virginia, storm surge flooding threatens 149,000 people, 72,000 homes, and 278,000 acres of land in the coastal zone at an elevation below 5 feet. The three cities with most exposed population? Virginia Beach, Chesapeake, and Norfolk

* In Delaware, storm surge flooding threatens 12,000 people, 13,000 homes, and 46,000 acres of land in the coastal zone at an elevation below 4 feet. The three cities with most exposed population? New Castle, Wilmington, and Bethany Beach

(Climate Central cautions the vulnerability numbers above are based on average reference 100-year flood levels in these states, and that the flood levels and vulnerability statistics at specific locations will vary.)


What the Potomac would look like with a 10 foot storm surge. Climate Central finds there is more than a 1 in 6 change that sea level rise + storm surge + tide will exceed 10 feet by 2030. (ClimateCentral.org)

An interactive map on the Climate Central website allows you to visualize land loss for increases in the water level ranging from 1 to 10 feet, resulting from a combination of sea level rise and a hypothetical storm surge. For each foot of land loss in such a scenario, Climate Central calculates the populatation, homes, and land area affected.

For example, in Washington, D.C., a storm surge-related water level increase of 10 feet has a 19% probability of occurrence by 2030 with global warming, and would affect 6,070 people, 2,656 homes, and 2,549 acres along the Potomac.

(Climate Central notes land, housing and population vulnerability estimates are based on 2010 Census data and on land elevations relative to potential water levels, and do not take into account potential protections.)

Finally, the report offers sea level rise projections through 2050. These projections typically range from 13-17” for the mid-Atlantic coast, with a 90 percent confidence range of 6 inches to about 2 feet. In most of these locations, sea level rise over the last 50 years was about 6-8 inches.

Related: Study: global warming related sea level rise poses big threat to Washington, D.C.

By  |  11:28 AM ET, 03/14/2012

Categories:  Latest, Climate Change

 
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