cover La.
By BOB ANDERSON
Environmental editor
Hurricanes could inundate many inland cities and communities in Louisiana that consider themselves safe from the great domes of water pushed ahead of the storms, LSU researchers say.
Advocate photo by Bob Anderson
Even a category 3 hurricane, with winds up to 130 mph, could push a storm surge over New Orleans' hurricane protection levees, like this one, and into the city, which has many areas below sea level, LSU researchers say.
And it would only take a category 3 storm, packing winds of up to 130 mph, to shove such a massive surge through Lake Pontchartrain into New Orleans, much of which is below sea level, their computer models indicate.
The wrong storm could put 20 ft of water in Jackson square, leaving the statute of Andrew Jackson under water, said Robert Eichhorn, director of emergency management for New Orleans.
"If you don't evacuate New Orleans, the best thing you can do is tie a tag around your toe so we can identify your body," said Brett Krieger, director of the state Office of Emergency Preparedness.
Hurrican season officially started Sunday.
Evacuating people into most tall buildings would be sending them into "death traps," where winds could blow glass and people out of the buildings, Eichhorn said.
A category 3 storm would put most of St. Bernard, Terrebonne, Jefferson, St. John, Lafourche, St. Charles and St. Mary parishes under water.
It would even flood large parts of Livingston, Iberville, Ascension, Assumption, Tangipahoa, St. Martin, and St. Tammany parishes, the computer model indicates.
The amount of flooding a storm can cause in a given area depends on its strength, its track and its forward speed, with slow moving storms pushing more water ahead of them, said LSU engineering Professor Joe Suhayda, who is running new storm surge models for emergency officials.
A category 5 storm, with winds over 155 mph, running up the middle of the state would flood everything up Bayou Lafourche for more than 70 miles as far as Napoleonville.
The surge from that same storm would flood Houma and Thibodaux, which is more than 30 miles from the coast, and push water to the outskirts of Plaquemine, the model indicates.
Just about everything south of Interstate 10, populated by 2.2 million people is now subject to hurricane flooding, Suhayda said.
Danger to south Louisiana is growing worse because of development and land loss, coastal specialists said.
Deterioration of barrier islands and coastal marsh, combined with land subsidence and sea-level rise are making Louisiana ever more vulnerable, said LSU coastal researcher Ivor Van Heerden.
While all of south Louisiana is at risk, the storms with the potential to kill the most people are ones that shove huge surges into Lake Pontchartrain, which has heavily populated areas on its north and south shores.
"Most people have the misconception that the threat to New Orleans is from the Gulf, but the threat is really from the lake," said state Climatologist Jay Grymes.
New Orleans should be viewed as a coastal city much of which is below sea level, officials said.
A hurricane could rapidly push an 18-foot-high surge into the lake, the models run by Suhayda show.
The work of another LSU researcher, Greg Stone, adds a frightening dimension:
Hurricane surges in Lake Pontchartrain could be topped with waves of up to 10 feet.
Neither the seawall at Mandeville nor the hurricane protection levee at New Orleans could handle the kinds of storm surges Suhayda's models project, even without the waves atop them, emergency officials concede.
A surge is a gentle rise compared to the waves on top of it, which can batter buildings and other structures, Suhayda said.
The waves make it easier for surges to wash over and damage hurricane levees and buildings and to block evacuation routes, Stone said.
Waves atop storm surges could pound over the Causeway's guard rails hours before the eye of a storm ever reached New Orleans, he said.
Combined with the flooding hurricanes have shown that they can cause along I-10 in both directions from New Orleans, the high waters and waves could further shorten the window of evacuation for the city, researchers said.
Emergency officials concede that complete hurricane evacuation of New Orleans is unrealistic, saying it would take three days notice and overcoming apathy to even come close.
The combination of a large population and a limited road system that floods makes evacuation difficult, according to officials with the Jefferson Parish Emergency Operating Center.
Andrew, a category 4 hurricane, with winds from 131-155 mph, was just a tropical storm 72 hours before it hit Louisiana in 1992. Hurricane specialists can't accurately predict how big a storm is going to be or where it will hit land that far ahead of time, Krieger said.
Even though it was obvious Hurricane Andrew posed a severe threat to New Orleans before it settled on a course through the Atchafalaya Basin, "people didn't really start to leave until 16 hours before Andrew hit," Krieger said.
Starting that late leaves only a few hours before the evacuation has to be stopped to prevent people getting trapped on the Causeway or I-10, he said.
Because of the damage Andrew caused in Florida, more people got out of New Orleans than usual, but still only 13 to 14 percent evacuated, Eichhorn said.
People who have remained dry behind hurricane protection levees during small or distant storms may not realize how drastically things can change once a section of that levee fails.
"People were found drowned in their attics after Hurricane Betsy, because places went from having no water to having 20 feet of water in 15 minutes," Krieger said.
Levees "do a very good job in protecting communities in minimal hurricanes," a National Weather Service report says, but adds, "most levees in southeast Louisiana would be overtopped from a direct strike by a slow moving, major hurricane."
The Red Cross has decided it's too dangerous to provide hurricane shelters in New Orleans or anywhere south of I-10, but the state will supply some last minute survival sheltering for people who don't leave the city, Krieger said.
The idea will be to try to get them into the most stable buildings and high enough so they don't drown, but the quick influx of water when levees are topped is still likely to cause widespread loss of life, Krieger said.
Disease could follow the storm as emergency officials deal with unsanitary conditions, lack of drinking water and standing flood waters, he said.
It could take three days for help to reach some of these people, Eichhorn said.