Levee modeling study to provide technical data for rebuilding New Orleans

To provide essential data for the rebuilding of the ravaged levees in New Orleans, engineers from Rensselaer Polytechnic Institute will be studying small-scale models of sections of the flood-protection system. The researchers will replicate conditions during Hurricane Katrina by subjecting the models to flood loads, supplying important information to help the U.S. Army Corps of Engineers prepare the city for next hurricane season and beyond.

The researchers will build and test models of typical levee sections from several locations in New Orleans, including the 17th Street Canal and the London Avenue Canal.

As part of the Corps' Hurricane Katrina Interagency Performance Evaluation Task Force (IPET), the project will take advantage of the facilities at Rensselaer's Geotechnical Centrifuge Research Center, which is partially funded through the National Science Foundation (NSF). Two Rensselaer engineers will be leading the effort: Tarek Abdoun, principal investigator and associate professor of civil and environmental engineering; and Thomas Zimmie, professor and acting chair of civil and environmental engineering.

"In addition to studying the damaged structures in the aftermath of the hurricane, we also can model the conditions that were occurring during the storm," Abdoun says. "This will provide decision makers with the best scientific information available as they proceed with the rebuilding process."

Zimmie was a member of the NSF-funded team that investigated levee failures in the immediate wake of the storm. In the team's preliminary report, researchers noted that there was not one simple answer as to why the levees failed. The field observations suggested a number of possible causes, according to Zimmie.

At the 17th Street Canal, the foundation is a complex combination of peat and weak clays, which may have caused this levee's failure, Zimmie says. Likewise, at the London Avenue Canal, a section of fine sand under the levee might have been the culprit.

"Until all the physical evidence has been analyzed, we will not have a complete picture of what happened," Zimmie says. "The information we collect from these centrifuge models will provide some hard data to back up our preliminary observations, helping us to better understand how levees respond under extreme conditions."

Rensselaer's 150 g-ton centrifuge, which is one of only four of its kind in the country, has a large mechanical arm that can swing model structures around at 250 miles per hour, exerting forces real structures would face only at catastrophic moments.

"Suppose we want to test a levee that is 100 feet high," Abdoun says. "We can build a model that is only one foot high and then spin it around at 100 g, making it equivalent to a 100-foot-high levee. We can simulate all kinds of structures under just about any failure condition -- earthquakes, explosions, landslides -- and we can do it relatively fast at a very reasonable cost."

A system of advanced sensors will measure the response of the levees in both the vertical and horizontal planes, and cameras will be mounted around the models for visual observations.

The research at Rensselaer will be supplemented by modeling studies at the Army's Centrifuge Research Center in Vicksburg, Miss. The IPET final report, which is scheduled to be completed by June 1, will be validated by an external review panel from the American Society of Civil Engineers (ASCE). The National Academies has assembled a multidisciplinary, independent panel of acknowledged experts to review and synthesize the IPET and ASCE efforts. The National Academies panel will report its findings and recommendations directly to the Assistant Secretary of the Army for Civil Works in the summer of 2006.

Source: Rensselaer Polytechnic Institute

Related stories:

Senate hearing focuses on repairing levees in New Orleans
It is clear that there were multiple causes for the levee failures in New Orleans, but researchers need to gather more data to better understand what they were and how to rebuild properly after the devastation caused by Hurricane Katrina, according to testimony today before the U.S. Senate Committee on Environment and Public Works. Tom Zimmie, professor and acting chair of civil and environmental engineering at Rensselaer Polytechnic Institute, offered his perspective on the degree to which the preliminary findings on the failure of the Gulf Coast levees are being incorporated into the restoration of hurricane protection.
New Orleans-style disaster could happen again - in California
Is California vulnerable to a New Orleans-style levee break?
"The land in the Sacramento-San Joaquin Delta, where California's two great rivers drain into San Francisco Bay, lies as much as 20 feet below sea level," warns Jane Wolff, author of Delta Primer: A Field Guide to the California Delta (2003). "If the levees that protect the region fail, we will lose valuable farmland, a unique ecological system and the centerpiece of the state's water-supply system."
Rensselaer engineers to inspect levees
Rensselaer Polytechnic Institute scientists are going to New Orleans as part of an expert team investigating levee failures caused by Hurricane Katrina.
New Orleans levee under threat as Gustav tears New Orleans under flood threat as Gustav tears into US coastinto US coast
Ferocious rain and wind gusts unleashed by Hurricane Gustav pushed water cascading over protective works in New Orleans Monday three years after Katrina swamped the fabled jazz city.
The technology to make 'Speed Racer' cars
The opening of the new “Speed Racer” movie coming out nationally on May 9 has meant weeks of fast-paced fun for 8 juniors in the University of Cincinnati’s internationally recognized School of Design, part of UC’s top-ranked College of Design, Architecture, Art, and Planning.
On shaky ground: UH Prof finds geological faults threaten Houston
After finding more than 300 surface faults in Harris County, a University of Houston geologist now has information that could be vitally useful to the region’s builders and city planners.
Geologist decries floodplain development
Midwesterners have to be wondering: Will April be the cruelest month? Patterns in the Midwest this spring are eerily reminiscent of 1993 and 1994, back-to-back years of serious flooding, with the Great Flood of 1993 causing nearly $20 billion of economic damage, damaging and destroying more than 50,000 homes and killing at least 38 people.
Plastic bags killing Queensland’s turtles
A group of University of Queensland researchers are urging Queenslanders to avoid littering the state's marine environment during the upcoming Easter holiday weekend.

News discussion:

Space & Earth science news