Wednesday, May 18, 2011

The Great Flood of 2011 (Part XI)

Parishes work to block bayous, canals

Workers direct the placement of a steel piling near the shore of Bayou Boeuf on Tuesday afternoon. The St. Mary Levee District is installing a wall of pilings, fortified by barges, to block the flow of water entering the bayou as a result of the Morganza Spillway opening to relieve high water on the Mississippi River.
Show CaptionHeather McClelland/The Advocate

  • Advocate staff writers
  • Published: May 18, 2011 - Page: 1A

AMELIA — Murky brown water gushed through a 100-foot-wide gap in a new wall of sheet pile nearly spanning Bayou Chene in St. Mary and Terrebonne parishes Tuesday.

That gap and a smaller one on the bayou’s far shore south of Amelia were all that was left mid-Tuesday afternoon to finish a 1,000-foot wall intended to divert high water headed south from the Morganza Spillway.

“We’ve done a year’s work in a week,” said Bill Hidalgo, president of the St. Mary Levee District, which is spearheading the $6 million project. He said pile-driving could be finished by Wednesday.

The plan borrowed from a similar idea in 1973, the last time Morganza was opened, when a barge was sunk in the bayou to stop flood water.

The spillway in Pointe Coupee Parish was opened Saturday to relieve high water in the Mississippi River and to divert it down the Atchafalaya Basin and into the lower Atchafalaya River, which spills into Bayou Chene.

Pronounced like “shane,” Bayou Chene ties into Bayou Boeuf and whips around Avoca Island south of Amelia and U.S. 90 toward the lower Atchafalaya River.

Hidalgo and other officials believe the bayou is a conduit for high water in the Atchafalaya, carrying it northeast toward Amelia.

That flow leads to backwater flooding in Terrebonne, Lafourche, St. Mary, St. Martin and Assumption parishes, possibly even as far as Iberville and Pointe Coupee parishes, Hidalgo said. Levee protection is less extensive or does not exist in many of these areas.

The district is trying to seal off the bayou temporarily and force water to move across land in a wooded swamp to the south, Hidalgo explained.

Mimicking the 1973 plan, the levee district sank a 500-foot-by-120-foot submersible barge to act as a guide for pile-driving that began Saturday and to work as a counterweight against the rising flood water in Bayou Chene.

The sunken 32-foot-tall barge sits about six feet above the water line in the middle of the bayou as interlocking sheet pile runs on one side. Two other barges are behind the other stretches of sheet pile being lined with riprap nearer to the shores.

The bayou is about 26 feet deep where the wall is, Hidalgo said

Ken St. Germain, manager and co-owner of the Pierre Part Store in Assumption Parish, heard Hidalgo’s plan during a Friday community meeting in Pierre Part.

Residents are still sandbagging and preparing for high water, St. Germain said, but the talk gave residents confidence that the worst flooding could be averted.

“I think everybody left a lot more secure after that meeting,” St. Germain said.

Hidalgo said levee district officials are hoping the wall will cut the height of backwater flooding by two feet if not more.

Others are less certain. Diverted water could end up going through the swamps south of Bayou Chene and turn back north, leading to some backwater flooding, some said.

“It’s highly possible that the water would find another way. It’s just a complicated web of bayous and channels down there. It is really hard to say,” said Sam Bentley, associate professor and Harrison chair in Sedimentary Geology for the LSU Department of Geology and Geophysics.

At the same time, Bentley said the idea is an interesting one that might work.

Hidalgo said levee district officials have had their own scientific evaluation done and believe the plan will work.

Workers also are placing sandbags in pipeline corridors, cutting through the swamps south of the bayou to block water.

Morgan City Mayor Tim Matte said even a few inches of reduced water height could stop the worst flooding in unprotected, low-lying areas on the city’s back side, such as Stephensville along La. 70.

“If we can keep the water out of some of those homes, we can maybe save some folks real misery,” he said.

Hidalgo said officials will seek a permanent replacement — with a gate that can open and close — if the temporary wall works.

Shoring up levees

St. Mary Deputy Jim Broussard said flood preparation efforts were moving along smoothly Tuesday.

“We’re getting into a rhythm,” Broussard said.

To protect against backwater flooding from the Franklin Canal, workers drove sheet piles into the canal, creating a makeshift dam, Broussard said.

Officials had already completed similar work in the Hanson Canal, located between Garden City and Franklin, and in Yellow Bayou, to the east of Franklin, Broussard said. In the past, backwater flooding from Yellow Bayou has forced officials to close U.S. 90 in Centerville, Broussard said.

Franklin Mayor Raymond Harris Jr. said hurricanes have led to flooding from the Franklin and Hanson canals. Damming both canals should prevent either from flooding, he said.

Work to build temporary levees along the Bayou Teche in subdivisions around the Franklin downtown area was also expected to be completed Tuesday, Harris said.

“We don’t think we’re in great danger (of backwater flooding) there, but we’re taking precautions to be safe,” Harris said.

The work will protect about 1,000 people who live near the canals, Harris said.

Meanwhile, the northerly winds, which have helped to reduce flooding in some areas by pushing water south into the Gulf of Mexico, are expected to switch to southerly winds beginning Tuesday night, Broussard said.

After taking a flight over the spillway, St. Mary Parish Councilman Charles Walters warned against complacency.

With only 15 of the Morganza Spillway structure’s 125 gates open, there is still “some serious water coming down here” Walters said. He said he expected to see water levels increasing within the next couple of days.

“There’s no sugarcoating this: We’re going to get some water,” Walters said Tuesday. “We can’t let our guard down at all along the front lines.”

Meanwhile, flood prevention efforts, including sandbagging and levee building, continued around-the-clock in the parish. Walters said the goal is to provide threatened areas with 5-feet-plus of flood protection.

He said no structures or homes have flooded yet, although it is starting to flood in unprotected areas of Amelia, a community to the east of Morgan City.

“This is not going to come and go; this is going to come and stay and that’s what we’re preparing ourselves for right now,” Walters said.

Waters continued to rise in St. Martin Parish but the flood water has not yet inhibited travel on the roadways, said Maj. Ginny Higgins, spokeswoman for the St. Martin Parish Sheriff’s Office.

In St. Landry Parish, Jimmy Darbonne, spokesman for the Sheriff’s Office, said about 70 people who live within an area under a mandatory evacuation order have opted to stay. Officials are not forcing residents from their homes.

Darbonne said there had been no noticeable change in water levels from Monday to Tuesday.

Water moves slowly

The river water was moving through the basin slower than the U.S. Army Corps of Engineers predicted.

The corps used information from the 1973 floods to help model how water would flow when the Morganza Spillway opened, but there have been changes in the landscape since then, said Tom Holden, deputy district engineer for the corps’ Programs and Project Management.

More crawfish ponds, more roads, more trees and the drought conditions the state is experiencing have all contributed to slowing down that flow, Holden said.

Despite the slow-moving water, the Governor’s Office of Homeland Security and Emergency Preparedness estimated Tuesday that more than 5,000 people have evacuated from St. Landry, St. Martin, Concordia, Avoyelles, Catahoula, East Carroll, Madison, and Pointe Coupee parishes, Gov. Bobby Jindal said.

The Louisiana Public Service Commission said Tuesday that utilities have been cut off to more than 1,000 homes and 88 businesses in Pointe Coupee, Avoyelles and Concordia parishes due to high water.

“Bottom line, it’s still headed our way. This is a serious flood event. It will be a problem for weeks,” Jindal said.

He said the water will take “a couple days” to reach Morgan City, “maybe Friday.”

Even with the spillway’s gates open, the Baton Rouge area will likely have high river levels for up to three weeks, he said.

Jindal said state officials are also preparing for another more pesky problem: snake bites. The Louisiana Department of Health and Hospitals and Louisiana Poison Control are working with hospitals to make sure there is enough anti-venom to respond to an anticipated increase in snake bites, which typically occur during and after flooding.

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