WASHINGTON, D.C., and SACRAMENTO, Calif.—A four-year, three-phase project by the U.S. Department of Homeland Security’s (DHS) Science & Technology (S&T) Directorate—the Levee Strengthening and Damage Mitigation Project—seeks ways to evaluate and strengthen the nation’s vulnerable system of levees. In the first phase, researchers will identify potential technologies and procedures that can rapidly and affordably indicate problem locations along a levee, strengthen these existing areas, provide designs for new levees, and repair any breaches. Subsequent phases will test and demonstrate the technologies and procedures.
For example, the U.S. Army Engineer Research and Development Center has developed the Levee Condition Assessment Technology, or LevCAT, which combines geophysical instrumentation with airborne and ground-based research to "see" weak soil under levees.
In early September, the California Department of Water Resources (DWR) began a month-long levee evaluation program using airborne electromagnetic surveys. A helicopter carried an aerial sensor suspended about 100 feet above the ground during survey flights over Central Valley levees and levees near Marysville, Yuba City, Sacramento, Woodland, Stockton, and Lathrop. According to the DWR, the sensor measures variations in the ground’s electrical conductivity to depths of more than 100 feet. The goal is to map important changes in soil types and ground conditions, identifying zones where permeable soils are present or excessive water penetration is taking place.
The DHS also cites a loss of natural buffer zones as an important factor impacting the effectiveness of the nation’s levees. River basins, deltas, and savannahs are being congested with soil and debris. Human development and residual waste is causing the surrounding land to sink, and as salt water rushes in, thick expanses of wetland, mangroves, trees and grasses are poisoned. Without these buffers, storms can push sea surges quite a distance inland. And, as ocean levels rise, low-lying cites will have to protect themselves by using some sort of barriers and pumps to help keep the rising waters out.
The Levee Strengthening and Damage Mitigation Project also aims to develop approaches and technologies that will duplicate the effect of marshland and reduce the strength of surges. Solutions being considered include inflatable and drop-in structures that last long enough to prevent severe damage, fast-growing vegetation to imitate the effect of marshlands rapidly in lowering tides, and ways to reroute flood waters and floodproof critical infrastructure.
GEI Consultants, Inc., announced in September that its work on the Bear River Setback levee in Yuba County, Calif., earned certification from the U.S. Army Corps of Engineers. The 10,000-foot-long, $51 million Bear River Setback levee will give the Bear River additional channel capacity and lower the water surface profile by about 3 feet during major flood events. GEI is part of DWR’s Urban Levee Evaluation team that is conducting geotechnical evaluations of the Marysville, Sutter County, American River, and San Joaquin Area Flood Control Agency levee system.
The DHS’s Science & Technology Directorate projects, called Homeland Innovative Prototypical Solutions, or HIPS, are designed to deliver prototype-level demonstrations of potential "game-changing" technologies in two to five years. They come with a moderate-to-high risk of failure, the DHS admits, but they can also yield a high payoff if successful.
"All of these goals are enormously ambitious, but that’s the nature of the work," said Wil Laska, who manages the DHS levee project. "Right now, the S&T Directorate is looking at just about any decent idea."