August 24, 2006

Lessons from Katrina to find worldwide uses

BRIAN BAKER

staff writer

TORONTO

So much technical investigation has gone into the levee deficiencies in New Orleans after Hurricane Katrina that the findings fill almost 6,200 pages of an Interagency Performance Evaluation Task Force (IPET) report.

The American Society of Civil Engineers (ASCE) convened the External Review Panel (ERP) to review the results of the IPET report, and the findings will be released to the public Aug.25.

“The ERP has come across the points that are really important to the rebuilding of New Orleans, and much of it can apply to communities across the country in terms of how we protect against hurricanes,” said Joan Buhrman of the American Society of Civil Engineers.

The IPET report covers lessons learned, geodetic vertical and water level datum, documentations of the character of the hurricane protection system, forces experienced by protection structures during Katrina, providing input to repairs and ongoing design and planning efforts.

“One of the issues was why some of the levees failed,” said Buhrman.

The I-walls built on top of the levees were in question. In order to make the levee higher to prevent storm surges, the walls must be widened as well. The suggested replacement for the I-wall foundations were T-walls, which are inverted.

The total number of breaches along the Hurricane Protection System in New Orleans was 46.

“Had all the structures been built to design elevations, there would have been less overtopping,” summarized in an IPET report.

The same report noted that four breaches occurred before water levels reached design elevations because of I-wall foundation failures. In all of four cases, water flowed into the gap created in the waterside of the flood wall, weakening the soil, eventually leading to instability and failure.

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