Tuesday, January 17, 2006

Man Let Us Down Not Nature

Expert: Post-Katrina flooding would have been less severe if levees held up

08:33 AM CST on Tuesday, January 17, 2006

Dave McNamara / WWL-TV News Reporter

If all of the levee systems in the Greater New Orleans area had performed the way they were supposed to, storm surge computer models have shown most of the city would have been spared catastrophic flooding in Hurricane Katrina, according to Dr. Hassan Mashrique, a researcher at the LSU Hurricane Center.

Mashrique analyzed Katrina's storm surge. He said even if the levees had not failed, Katrina still would have topped some levees and flooded parts of New Orleans, but the difference would have been dramatic – with fewer neighborhoods under and fewer fatalities.

"There would have been minor flooding, two to three feet, in the Lower Ninth Ward. Most of the Chalmette area would have been dry,” said Mashrique.

In Mashrique’s computer model—which displayed the depth of flooding if the levees held up during the storm—Lakeview would have remained dry, including much of Chalmette. Only areas south of Chef Highway in New Orleans would have been inundated with five to six feet of water.

Katrina flattened most of the 17-foot high hurricane protection levee along the Mississippi River Gulf Outlet, sending a massive surge toward St. Bernard Parish. The model shows that if the big levee had not collapsed, water would have spilled over the levee for only a short period of time.

“…But this would have been minimal for two to three hours. So in real time, by 10 or 11 o’clock, the overtopping would have stopped and people would have turned on pumps,” Mashrique said.

If the Ninth Ward Levee holds during Katrina, the LSU computer model shows water a foot or two higher than the floodwalls spilling into one neighborhood for a few hours. Unfortunately, the levee breaches were like a dam collapsing, and the flooding that resulted was catastrophic.

“All of a sudden you have a twenty foot wall of water, like a cannon of water, if the wall held, and it was a spilling over the wall, then it was a gradual creeping of water into your house," Mashrique said.

Mashrique said levees needed to be strong enough that they do not erode and collapse, and strong enough to absorb the energy of a rapidly moving storm surge.

“It's not a location issue. It's not a dangerous place issue. It's how engineers build their difference,” he said.

Mashrique said Katrina should be a wakeup call and not the standard for levee reconstruction. And these computer graphics show just how different it might have been, if the levees hadn't failed.

The LSU Computer models also showed that flooding from Katrina's storm surge would have been much worse if the hurricane track had passed over New Orleans.

No comments: