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Termites Partly To Blame For Destruction Of Floodwalls

October 15, 2008

Three years after Hurricane Katrina devastated New Orleans, people still speculate over causes of the destruction of the city’s floodwall system. A new article in the fall issue of American Entomologist (Vol. 54, No. 3) suggests that Formosan subterranean termites played a large role.

Author Gregg Henderson, a professor at the Louisiana State University AgCenter, discovered Formosan subterranean termites (Coptotermes formosanus Shiraki) in the floodwall seams in August, 2000 ““ five years before Katrina struck ““ and noticed that the seams were made of waste residue from processed sugarcane. Known as bagasse, this waste residue is attractive to Formosan termites.

After the dikes were breached in 2005, Henderson and his colleague Alan Morgan inspected 100 seams for evidence of termites, including three areas where major breaks in the walls had occurred. 70% of the seams in the London Avenue Canal, which experienced two major breaks during Katrina, showed evidence of insect attack, as did 27% of seams inspected in the walls of the 17th Street Canal.

The Formosan subterranean termite originates from China, where it has been known to damage levees since the 1950s. Besides eating at bagasse seams, the termites may have contributed to the destruction of the levees of New Orleans by digging networks of tunnels, which can cause “piping,” sending water through the tunnels and undermining the levee system.

“I believe that the termites pose a continuing danger that requires immediate attention,” Henderson writes. “The fact that termites cause piping in levees must be accepted.”

The author further suggests that New Orleans’ 350 miles of levees and floodwalls should be surveyed for termite damage, and that treatment of the floodwalls and nearby trees may be necessary to avoid future disasters. Henderson will demonstrate one survey method using ground-penetrating radar at the ESA Annual Meeting in Reno, Nevada, November 16-19.

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