The Army Corps of Engineers was preparing Tuesday to install emergency barriers on two key canals to protect against new flooding as Hurricane Rita approached the Gulf of Mexico, posing a new threat to the city’s badly damaged drainage system.
Col. Duane Gapinski, who is leading the effort, said the steel barriers should prevent a massive re-flooding of the city unless Rita grew in intensity or changed to a course closer to New Orleans.
Experts at the National Hurricane Center in Miami were predicting that Rita would make landfall in Texas between Corpus Christi and Galveston, meaning that its high winds and storm surges would come close to hitting New Orleans and probably cause significant rain. The center early today upgraded the storm to a Category 3 hurricane.
“It is getting uncomfortably close to a track that would put gale-force winds into the Mississippi River delta,” said Stephen Baig, a surge expert at the center. “It would not take very much of a turn to the right to push gale-force winds into New Orleans.”
Three weeks after Hurricane Katrina badly damaged New Orleans’ levees and storm walls, some Army units sent to restore order to the city were planning to withdraw to inland bases until the threat of Rita had passed. Vast sections of residential neighborhoods were deserted.
Gapinski said he would decide about noon today whether to order installation of steel barriers to seal off two main canals that normally allow water to drain into Lake Pontchartrain. A third badly damaged canal cannot be shored up further, and a major surge could re-flood St. Bernard Parish and the 9th Ward, he acknowledged.
“The situation is intense,” Gapinski said. “But we are determined. Certainly we are not panicking. We are doing all we possibly can with the resources we have.”
The steel barriers would protect the already damaged canal levees from a 10-to-12-foot storm surge blowing in from Lake Pontchartrain to the north. Katrina caused a 12-foot surge in the lake that sent water up the 17th Street and London Avenue canals, causing several massive breaches that flooded the city.
Those breaches have been repaired with sandbags and fill, but the new portions remain about 9 feet below the normal level of the storm walls and are vulnerable to smaller surges. By sealing off the canals at their openings near the lake, the Army hopes to provide a fair measure of protection against a Category 3 hurricane.
The picture is not quite as good on the Inner Harbor Navigation Canal, a large waterway that connects the Mississippi River and Lake Pontchartrain.
The channel sustained heavy damage from Katrina, and the repaired sections are about 8 feet below the normal storm wall height.
It is not possible to seal off that channel because it is a much larger and deeper waterway. In addition, levees far to the east of the city along the Mississippi River Gulf Outlet are in bad condition.
Gapinski said the city was protected only from a 5-to-6-foot surge from the east. Katrina caused an estimated 18-foot surge from the east.
Gapinski said if the repairs did give way or a big surge entered from the east, it could potentially re-flood the 9th Ward and St. Bernard Parish.
“I can only repair so many places,” he said. “I have only so many resources here. It is not inhabited, and it already had significant damage.”
Even if New Orleans is not hit with a surge from the Gulf of Mexico, significant rain could cause localized flooding. The city’s massive pumping system, which includes 22 stations throughout the city, remains badly damaged with only a third of its normal capacity. Because much of New Orleans is below sea level, almost every drop of rain must be pumped out.
The Army Corps has completed its effort to pump New Orleans dry before Rita approaches. Gapinski said computer models completed Tuesday indicated that 3 inches of rain in six hours could cause 2 feet of flooding in some previously flooded neighborhoods in the central city. Such a flood would take a couple of days to pump out. If the city had all of its pumps working, it could easily handle that much rainfall without flooding.
Two hurricanes hitting near the same city in the same year is hardly without precedent. Just last year, Hurricanes Francis and Jean went into the same area of eastern Florida, Baig said.
Another risk facing New Orleans is the phenomenon of a strong hurricane raising water levels in the Gulf of Mexico, Baig said. A current of warm water normally exits in the gulf through the Straits of Florida, but a hurricane can temporarily block the flow, backing up water by 2 feet from Texas to Florida. So even if Rita misses New Orleans, the city could see higher-than-normal tides, along with residual winds and rain.