BATON ROUGE, La. — Tropical Depression Isaac, weakening from tropical storm status as it made its way across land, continued to cause problems across Louisiana and Mississippi on Thursday.
The torrential rains will now move into Arkansas and parts of the Midwest that have suffered through the summer with far too little water, not too much of it.
As New Orleans breathed a sigh of relief over the $14.5 billion in levee defenses that now ring the city, other parts of the state without such protections were not so lucky. The storm’s surge caused water to rise nine feet on the north shore of Lake Pontchartrain, flooding towns like Slidell; west of the lake, the waters inundated LaPlace and the surrounding area. Emergency crews tried to take dangerous pressure off a weakened dam on Lake Tangipahoa in Mississippi and to release penned-up water in the drenched communities of Plaquemines Parish southeast of New Orleans.
Federal officials warned that the storm’s risks were not past. “Whether a community is beginning the cleanup process, or still feeling the effects of Isaac, residents still need to be alert to the dangers that remain,” said W. Craig Fugate, head of the Federal Emergency Management Agency. “This is still a powerful storm and there are a number of areas both along the coast and inland that can be affected by strong winds, storm surge and inland flooding and tornadoes.”
During a morning news conference in Baton Rouge, Gov. Bobby Jindal said that more than 6,000 people had registered in shelters around the state, and more than 3,000 people were taken out of St. John the Baptist Parish alone.
As for the locally operated levee on the west bank of Plaquemines Parish, “it appears that the levee has held,” the governor said, adding that “the worst fears did not come true.”
At the east bank community of Braithwaite, floodwaters stood at eight feet in some areas, trapped within the local levees. The water level had dropped from a height of 14 feet, the Army Corps of Engineers estimated. The state drained off several feet, allowing some water to flow back into the Mississippi River through the Caernarvon diversion, a coastal restoration structure that normally sends fresh water and sediment from the Mississippi into the coastal bays and marshes of the Breton Sound.
On Thursday afternoon, work crews cut a notch in the parish-built levee to allow the water to flow out. “We anticipate we will be able to drain up to 70 percent of the water from the inundated area within a 24-hour period,” said Olivia Watkins, a spokeswoman for the state’s coastal protection and restoration authority.
The rest of the water, she said, will be removed with diesel pumps that had been trucked in.
In Mississippi, state workers tried to take water pressure off a rain-weakened Percy Quin dam at Lake Tangipahoa. A collapse of the dam could have caused a surge of water into the Tangipahoa River, which has flooded badly in years past and was already running high on Thursday because of the storm’s rainfall.
Tangipahoa Parish stretches down from the Mississippi state line to Lake Pontchartrain, and other than the city of Hammond consists largely of small towns and pastureland. Most of these towns lie just west of the Tangipahoa River. The parish has grown quickly in the years since Hurricane Katrina, as southern Louisianans moved north, but those who have been around a while are used to flooding.
“Folks that live here know better than anyone else, they know where the water went in 1983, they know where the water went in 1990,” Governor Jindal said in a briefing at the Tangipahoa emergency operations center in Amite City, La.
The controlled release of water was intended to take pressure off the dam, but was not expected to substantially raise the level of the river. The release will affect “about 20 homes,” said Christina Stephens, a spokeswoman for Governor Jindal’s emergency office, but will reduce the threat to the larger population along the river.
The collapse of the dam could have been devastating, and Louisiana officials ordered an evacuation of tens of thousands of people who live within half a mile of the river. Were the dam to burst, all of the village of Tangipahoa (population 1,200) would be underwater, said Michael Jackson, the mayor. He estimated that 85 percent of the residents had left for shelters in Kentwood or to stay with relatives. The village had flooded this time last year, just because of a bad rainstorm, so people knew their risks.
To many of those packing up, this was just an unfortunate but inevitable part of living in a floodplain.“You see, this is swamp,” said T. J. Ockman, 65, who lives not far from the river. His mobile home sits on stilts up on a hill and he does not think it should flood. Still, he was making trips back and forth between his trailer and his pickup truck, clomping up the stairs in his white shrimp boots, packing up his three dogs and a generator. “I’m no fool,” he said. “I was raised around the bayou. I’ve been through a few storms. I know from water.”
In Slidell, La., a city of about 30,000 people on the northeast shore of Lake Pontchartrain, floodwaters from creeks flowing into the area’s bayous inundated Olde Towne, a residential area and tourist destination, and Mayor Freddy Drennan encouraged residents in several neighborhoods to evacuate.
Louisiana’s lieutenant governor, Jay Dardenne, said that workers in state parks in St. Tammany Parish told him “there is more water than we saw in Katrina.”
At a junior high school in Slidell that served as a Red Cross shelter for the parish, the volunteer in charge, Ed Harris, had to go back to his own home to rescue his wife, Jeanie. “I got a text yesterday from her, she was scared. We’d gone through Katrina.” He went to pick her up, his truck pushing through the rising water. Now she was one of the 160 or so evacuees to join him at the shelter. They still did not know what happened to the house.
At the Baton Rouge news conference, Mr. Jindal said that the success of the New Orleans hurricane defenses would send a message. “If the proper flood protection systems are built, we can protect our people and our communities,” he said.
The investment around New Orleans pays off for all Americans, he said: “Protecting the Louisiana coast is good for Louisiana — it’s also good for this country” because of the importance of the seafood that comes from commercial fishing and the energy and taxes. “It’s a good investment for the country to be making,” he said. “It’s investing in the goose that’s laying the golden eggs.”