This week: Hurricane Sandy tops the 2012 disaster list, the silt total underestimated at Elwha Dam, the Morganza levee project swells in cost, using biomimicry to protect coastal cities, and the decaying thousands of bridges in America
Flood losses are expected to total approximately $10 billion in 2012, making it the third consecutive year of increasing flood damage in the U.S.—in large part due to Hurricane Sandy
Outside of Hurricane Sandy, most 2012 flood events occurred below the Federal Emergency Management Agency (FEMA) 100-year flood levels. In fact, freshwater flood activity through October indicated a decline in flood losses from 2011, on par with CoreLogic historical trend analysis.
Elwha dam-removal project held back as silt estimate too low (Seattle Times)
The new estimate is partly the result of discovering a long-standing error in mapping Lake Mills, with elevations recorded 20 feet higher than they really were back in 1917, Maynes said.
Those incorrect measures were passed along in a 1976 map used by engineers in their sediment estimates for the dam removal project, because the 1976 map had been marked as corrected — when it wasn’t.
The increased costs of the project are the result of a number of factors, including the more-stringent levee building standards the corps adopted after hurricanes Katrina and Rita in 2005. Those increased costs meant that even though the project had federal authorization, the estimated price of the project rose enough that the corps was required to do a post-authorization change report.
For flood-prone coastal areas in the post-Sandy era, biomimicry could provide fresh architectural solutions. American ground squirrels and prairie dogs, for example, essentially construct circular dikes that prevent rainwater from reaching their burrows below ground; similarly, circular plantings of trees and shrubs could funnel and slow stormwater, easing pressure on city sewers.
And plants’ cooperation techniques could influence coastal architecture. Peatland plants withstand unpredictable water levels from snow melt and heavy rains by clumping together into stilt-like rafts. Similarly, red mangrove trees crowd together to withstand the heavy waves of their coastal habitat, absorbing wave energy in their roots and forming a natural breakwater that protects shoreline.
Bridges have a life span, a limit to how long they can bear the weight and weather of daily stress. Then they need to be replaced. Generally they are built to stand for 50 years; the average bridge in the United States is 43.
That puts many of the nation’s 600,000 bridges at the end of their lives, with 70,000 of them officially judged structurally deficient last year. Pennsylvania leads the nation, with 5,906 troubled bridges. Virginia has 1,267, Maryland has 359 and the District has 30.
Bridges are just a fraction of the vast infrastructure boom that followed World War II and limped creaking and groaning into the 21st century.