By now, thewhatis well known: Hurricane Katrina was the costliest natural disaster inU.S.history, devastating 30,000 homes and producing an estimated $20 billion in damage.
Thewhy,however, is still being analyzed.
Joannes Westerink, a University of Notre Dame professor of civil engineering and geological sciences and a leading expert on hurricane storm surge, is among those trying to find the answers. He recently co-led the regional hydrodynamics team of the Interagency Performance Evaluation Task Force (IPET). IPET was an Army Corps of Engineers-led eight-month, $20 million performance evaluation of theNew Orleansand Southeast Louisiana Hurricane Protection System during Katrina that was conducted by 150 leading corps engineers, academics, and government and private sector scientists and engineers.
IPETs draft report was issued this month and at nine volumes and 6,000-plus pages. It is heavy reading in more than one sense. However, Westerink offers a simple explanation for the storms impact: size.
This was a huge storm, with evidence of 55-foot significant wave heights on Gulf (ofMexico) buoys, the highest ever measured,he said.Katrina was a Category 3 at landfall , but it was a Category 5 in the Gulf before landfall.
The IPET concluded that an effective hurricane protection system could have been built and would have substantially alleviated the flooding that inundated about 80 percent of theNew Orleansarea. However, theNew Orleanssystem was a patched up affair that provided inconsistent levels of protection and lacked sufficient backup mechanisms.
The report points out that there were 50 major breeches in drainage canal flood walls, andall but four were due to water overtopping the walls and eroding the levee earth that anchored them.
Westerink notes that the IPET reports findings already are being implemented as part of the Louisiana Coastal Protection and Restoration Project (LACPR). Both LACPR and the Federal Emergency Management Agency are using the Advanced Circulation Model, or ADCIRC, he helped develop to address flooding problems inNew OrleansandSoutheast Louisiana.
ADCIRC employs computer science, coastal oceanography, mathematics and engineering to forecast incoming storm surge. Storm surge is the wall of water pushed onto land as a hurricane comes ashore. It is actually a greater danger and cause of destruction and death during hurricanes than high winds. Storm surge exceeded 28 feet on theGulfCoastduring Hurricane Katrina.
Our model was accurate within a foot 55 percent of the time during Katrina,Westerink said.Our Notre Dame team will have made refinements by the end of the summer that will make it accurate within a foot 90 percent of the time.
One of the most disturbing IPET findings was that information used to determining how high flood barriers had to be was outdated and failed to take into account the fact that the ground level had subsided as much as 2 or more feet in the past three decades.
Westerink hopes that the vast amount of information IPET collected will help avoid such miscalculations in the future.
This was a tremendous effort that addressed every aspect of the problem, from hydrodynamics to economic damage to socioeconomic effects,he said.We now have much better technical answers needed to design a hurricane protection system and obtain an accurate estimate of its cost.
* Contact: * _Joannes Westerink, professor of civil engineering and geological sciences, 574-631-6475, westerink.1@nd.edu _ _
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