With New Orleans in ruins, hydrological engineers are looking to new technologies to bolster aging earthen levee systems. But so far, at least, the problem of holding back floodwaters has progressed little beyond the ancient and time-consuming technique of piling on more dirt.

Levees fail to hold back rising waters for two reasons: Either the water is too high and "overtops" the structure, or a weakness in the soil allows seepage to collapse the structure from underneath.

Levees provide a "very small margin of error," according to Neil Grigg, a professor of civil engineering at Colorado State University. Grigg said local agencies usually oversee levees, which are hard to keep in top shape. "Maintenance is difficult because you have animals burrowing through them and weeds growing through them," said Grigg, describing the use of soil to prevent floods as a primitive technology.

The Army is currently testing products that can temporarily raise the height of levees to determine if they can be assembled faster than the usual defense of filling and stacking sandbags.

The Rapid Deployment Flood Wall from Geocell Systems is a series of interlocking sections of plastic that are filled at the scene with sand or soil and can be layered as high as necessary.

The Hesco wall is a metal basket with fabric sides that is filled with soil. Hesco walls can be folded flat for easy shipment, according to Hesco Bastion director of operations Jared Lyons, who said his products are being used to protect against floodwaters in Texas and Florida.

The Portadam system is a series of metal rods that are bolted together and do not have to be filled with soil.

The Army will conclude testing and decide if any of the products meet its requirements by the end of the year, according to George Sills, a geotechnical specialist in the Geotechnical and Structures Laboratory at the U.S. Army Engineer Research and Development Center.

Developing new techniques to raise the height of levees quickly is a top priority...