Morganza Spillway may be opened next week to divert Mississippi River
By Mark Schleifstein, The Times-Picayune4 May 2011
The Corps of Engineers may open the Morganza Spillway near Baton Rouge next week to divert massive amounts of Mississippi River water into the Atchafalaya Delta. It would mark the first time since 1973 that the diversion structure has been used to prevent flooding.
TED JACKSON / THE TIMES-PICAYUNE Mississippi River water seeps beneath the Bonnet Carrie Spillway structure as record flood waters creep ever closer to the lower Mississippi River, Wednesday, May 4, 2011.
The tactic is the latest being debated as the state prepares for the river to reach record levels, after the repeated thunderstorms across parts of the Mississippi and Ohio river basins during the past three weeks. The water those storms generated joined an already swollen river that crested in late March and early April after a major spring snow melt.
Gov. Bobby Jindal, who flew over the spillway area with corps officials Wednesday, told reporters he has activated the Louisiana National Guard to assist with flood prevention. The corps has already announced that it expects to open the Bonnet Carre Spillway in St. Charles Parish early next week to move river water into Lake Pontchartrain.
If the Morganza is opened, it would be the first time the spillway has been used since the early 1970s, when another record high river threatened to destroy the Old River Control Structure, north of Morganza in Avoyelles Parish. That structure regularly diverts about 30 percent of the Mississippi’s water into the Atchafalaya watershed — comprised largely of farm and timber land — and blocks the entirety of the Mississippi from flowing down the Atchafalaya River.
In a message sent to New Orleans corps officials on Tuesday, Maj. Gen. Michael Walsh said hydraulics engineers have forecast that the Mississippi could be cresting at 1.9 million cubic feet per second at Red River Landing, below the Morganza Spillway and across from Angola State Prison. The "trigger" to open Morganza is a flow of 1.5 million cubic feet past that landing, a threshold expected to be reached a week from Wednesday.
Corps officials are quickly modeling the effects of opening Morganza on Morgan City, where several businesses are located on the water side of floodwalls, and other Terrebonne and St. Mary parish communities. Jindal said the state will use that modeling to make specific plans for evacuations, placement of sandbags and distribution of other resources. Corps officials said last week they would assist the state in making sandbags available to fight flooding along the river where levees may be low or compromised in some way.
The last time the Morganza Spillway was opened was April 18, 1973. (Times-Picayune archive)
"It’s like hurricane season: You hope for the best, prepare for the worst," Jindal said. "We haven’t seen flooding like this in quite awhile. The water will be higher and the duration will be longer" than what Louisiana has dealt with in recent years.
But, he noted, "The corps is not anticipating overtopping of mainline levees along the river."
Separately, Jindal has asked for federal activation of the guard so the state can seek reimbursement for its expenses.
The corps routinely notifies individuals who live or work within the Morganza Spillway area at the beginning of spring high water seasons that the spillway could be opened. Additional notices will be sent out over the next week, and individuals living in the spillway are expected to be contacted in person before an opening, a corps spokeswoman said. Corps workers already have begun rehearsing how to open the gates and operate other features of the control structure.
In addition, Terrebonne Parish President Michel Claudet on Tuesday declared a state of emergency because of potential flooding in the towns of Gibson, Bayou Black, Bull Run Road and Southdown Mandalay.
Corps officials also are debating when to begin opening the Bonnet Carre Spillway in St. Charles Parish. That could occur on Monday or Tuesday if the water volume reaches 1.25 million cubic feet per second at Red River Landing and is still rising.
Meanwhile, officials have stepped up levee inspections along the Mississippi and Atchafalaya rivers throughout Louisiana to search for seepage and sand boils, which are areas where river water tunnels under a levee.
On Tuesday, the corps dynamited a section of levee just north of Cairo, Ill., to open a spillway there in an effort to reduce pressure on levees around that town. The water flowing into farmland there may delay the timing of crests downriver, but is not enough to affect the ultimate crests.
A corps prediction on Wednesday called for a crest of 65.5 feet at Red River Landing, which would be 17.5 feet above official flood stage and 4.2 feet above the 1997 record. At Baton Rouge, where officials have built a clay berm along one levee segment to increase its strength, the crest of 47.5 feet on May 23, would be less than a foot below the record crest seen during the 1927 flood.
The two spillways are expected to keep the river level in New Orleans at 17 feet when it crests on May 24, four feet below the record 21-foot crest in 1927. On Wednesday afternoon, the river had risen to 14.7 feet at the Carrollton Gauge.
John Barry, vice president of the Southeast Louisiana Flood Protection Authority-East and author of "Rising Tide," a book about the 1927 Mississippi River flood, said the river is expected to overtop a low levee segment at the Bohemia Spillway, with water flowing east into wetlands in Plaquemines Parish.
Despite the high water levels, officials don’t expect to open all of the bays of either the Morganza or the Bonnet Carre spillway.
•••••••
Staff writers Bill Barrow and Matt Scallan contributed to this story. Mark Schleifstein can be reached at mschleifstein@timespicayune.com or 504.826.3327.
http://www.nola.com/weather/index.ssf/2011/05/morganza_spillway_may_be_opene.html