In the last 100 years, there have been two catastrophic levee breaches. The most recent breach, caused by hurricane Katrina, ended in millions of dollars of damage as well as the loss of over 1,836 lives and the disappearance of over 705 residents. This levee breach resulted in the flooding of over 80% of New Orleans, Louisiana.
The levee breach was caused by multiple flood surges in surrounding bodies of water. The first surge was caused by the dangerously high amount of rainfall. The second surge, however, was caused after the eye of the storm passed and the winds rose. These winds that blew towards land forced seawater swells upstream and towards the already endangered levees.
Levee breaches often occur as either water levels rise above levee levels, or by catastrophic failures. When the water rises above the top of the levee, it spills over and quickly erodes the soil and substrate below. This creates a positive feedback look which spirals out of control. The first release of water may not seem substantial, but it quickly erodes more soil, which allows more water to pass. This method of levee breaching often causes a narrow but deep path for the water.
The research portion of the Department of Homeland Security, The Science and Technology Directorate recently developed a method of preventing and stopping levee breaches. Their most promising idea which has been tested up to ¼ scale, has proven successful so far. This device is called a Portable Lightweight Ubiquitous Gasket, or PLUG. Its design is that of a floating device that fills up to 80% with water. The water currents caused by the levee breaches drag this device towards the breach, and the water pressure from inside the levee effectively pushes the device into the hole, sealing it. This method of stopping levee breaches is especially effective because it provides a method of slowing, or even halting, the flow of water even where heavy machinery cannot be transported.
To read the article from R&D Magazine, visit: http://www.rdmag.com/News/Feeds/2009/11/environment-mean-old-levee/