Saturday November 22, 2003

Preliminary results of a five-year study of New Orleans' hurricane risk show that about a third of local residents would not evacuate, and those who do try to leave to the west will be tied up in traffic jams despite plans to use both sides of the highway.

Ivor van Heerden, director of the LSU Center for the Study of the Public Health Impacts of Hurricanes, discussed his initial findings Friday at a special meeting of the monthly New Orleans Mayor's Environmental Breakfast at the district headquarters of the Army Corps of Engineers.

In addition to listing the frightening consequences of a hit on New Orleans, van Heerden also offered support for a couple of disregarded engineering projects that could protect the city from catastrophe.

Hurricane Center research shows that only 68.8 percent of the people would leave, and many of those would be stuck on Interstate 10 well before Kenner, the point at which all lanes on both sides would be used for westbound traffic.

The danger faced by those unable or unwilling to escape the city would be enormous, van Heerden said.

The bowl-like area between levees -- much of it 5 feet below sea level -- would be filled with water to depths of 19 to 22 feet. The water would contain a mix of oil, gasoline and toxic chemicals released from myriad storage tanks, cars, trucks, flooded homes, stores and industrial sites.

Of major concern, van Heerden warned, are the hundreds of storage tanks scattered throughout both commercial and residential areas.

"A high proportion of them are not properly tied down," he said. "Imagine a storage tank full of diesel lifted by flood waters, shearing its hoses, and its pipes working loose, and leaking.

"And because of the city's bowl setting, it's going to be difficult to flush out the chemicals that leak, to get them out of the system," van Heerden said.

Flood waters also will contain untreated sewage, which could cause an epidemic of gastrointestinal diseases, including giardia, cholera and typhoid fever. Mosquito-borne diseases also would be expected to increase.

Even a strong Category 3 or a Category 4 hurricane, with winds between 120 mph and 155 mph, would cause catastrophic damage throughout the community, he said.

Wind would cause at least minor damage to most buildings, but there's a chance of major damage or outright destruction of half the area's buildings. Most one- to three-story buildings would see damage to windows and roofs.

To reduce the risk of such devastation, Van Heerden recommends that federal and state officials developing a coastwide wetlands restoration plan revisit two previously rejected proposals.

Both proposals, van Heerden said, would dramatically increase protection from hurricane storm surge for the New Orleans area.

The city, he explained, now is vulnerable to surge that makes its way through Breton Sound toward eastern New Orleans from the south. It is also vulnerable to surge pushing into Lake Pontchartrain that may top levees along the lakefront or move inland in St. Charles Parish, where levees have not been completed.

<b>Reroute river</b>

The first proposal reroutes the Mississippi River into Breton Sound, abandoning the river's present bird-foot delta at its mouth.

The new path would build a new delta into the sound, with sediment drifting north into the eroding marshes surrounding Lake Borgne.

As the existing delta's sediments are reworked by wave action, a new concave barrier island will be formed, adding protection to the south of the city.

The second proposal is to build a barrier wall along the Interstate 10 twin span bridge between eastern New Orleans and Slidell. The wall would include two gaps to allow tidal action in Lake Pontchartrain, but would stop much hurricane storm surge from entering the lake.

Both proposals have been considered in some form and dismissed in the past. The first, the so-called "left turn" proposal, has been opposed by shipping interests concerned about the time it would take to complete such a project and its potential disruption of business.

A form of the lake barrier, including gates at the Rigolets and Chef Menteur passes, was successfully challenged in court in the 1970s, when it was recommended as part of the area's hurricane protection system.

<b>Coastal projects</b>

The Louisiana Coastal Area restoration study, written by a team of officials from the Army Corps of Engineers and other federal and state agencies, is expected to include a variety of projects using water and sediment from the Mississippi River.

Those projects include large freshwater diversions, cutting new crevasses through levees and riverbanks near the river's mouth, and using pipelines to transport sediment to areas far from the river.

Also among the projects are several that would build wetlands in Lake Borgne, but the lake barrier proposal is not included.

The projects will be collected into seven sets of alternatives, one of which will be selected to be presented to Congress for authorization next summer as part of the 2004 Water Resources Development Act.

The $5.5 million cost of van Herder's research is financed by the federal government and LSU. The project is being carried out by the LSU Hurricane Center, parent of van Herder's center.

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Mark Schleifstein can be reached at

mschleifstein@timespicayune.com or (504) 826-3327.