Swollen with two months worth of heavy rain that fell in Texas, Arkansas and Oklahoma and drained into its northern reaches, the rising Red River sent floodwater into neighborhoods, RV parks and farmland around Shreveport last week, including the house of Caddo Parish Sheriff Steve Prator.
The high waters in northeast Louisiana are now receding, although there’s still some street flooding reported in Pineville.
“We’re so far, so good,” Pineville Mayor Clarence Fields said Monday afternoon.
But what does all that water mean for southeast Louisiana as the high water in the Red River eventually makes its way south?
According to the National Weather Service, U.S. Army Corps of Engineers and state homeland security officials, it’s not much to be concerned about.
Even though 200,000 cubic feet of water per second is rushing through the Red River, the Atchafalaya River, which receives all the Red River’s water, has far more capacity, officials said.
The Atchafalaya’s depth and breadth is much larger than the Red River’s.
Water may be expected to rise on the Atchafalaya, but the rise isn’t expected to seriously threaten levees.
Jeff Graschel, National Weather Service service coordination hydrologist for the Lower Mississippi River Forecast Center, said water in the Atchafalaya is now flowing at about 380,000 cubic feet per second. The river needs flows of 750,000 cfs for the Atchafalaya to reach flood stage at Simmesport in southern Avoyelles Parish.
Even adding all of the Red River’s high water flows to the Atchafalaya’s wouldn’t push the river to flood stage, Graschel said.
Flood stage is the point at which the river would leave its natural banks but does not account for the man-made levees that line its banks.
Chris Guilbeaux, deputy director of the Governor’s Office of Homeland Security and Emergency Preparedness, said water also tends to pool and be stored in the swamps of eastern Avoyelles Parish before heading past the Corps’ Old River Control Structure. He said high water impacts are not expected to extend beyond Alexandria.
“Eight feet of water in Shreveport above flood stage may cause 8 inches of water in the Atchafalaya, so it’s nothing to worry about in the Atchafalaya Basin,” Guilbeaux said.
The Red River crested June 9 in Shreveport at slightly more than 37 feet, 7 feet above flood stage and the highest the river has risen since April 7, 1945, NWS data show.
While the Old River Control Structure ensures a 70-30 split of water flow between the Mississippi and the Atchafalaya rivers, the structure does not allow any of the Red River’s water to flow into the Mississippi River.
That means none of the Red River’s water ends up in the Mississippi to possibly affect Baton Rouge or New Orleans.
At the same time, these same officials said additional rainfall can affect projections.
Two things officials said they are watching are heavy rain expected in the Missouri and Ohio river valleys and Tropical Storm Bill, which is churning in the Gulf of Mexico and appears headed toward the Texas coast.
Though the Red River is expected to drop below flood stage by Friday in Shreveport, Guilbeaux said any rain from Bill that ends up falling on Dallas and other parts of northeast Texas or southeastern Oklahoma would send more water through the Red River again.
“We may be in for round two. We just don’t know how much,” said Lt. Bill Davis, Bossier Parish Sheriff’s Office spokesman.
Graschel said 4 to 6 inches of rain are projected to fall over the next six days in the Ohio and Missouri river systems, which feed into the Mississippi.
With the Mississippi already up, that could push water levels up farther on the Atchafalaya, too.
He said that could mean Morgan City, which is on the far southern reach of the Atchafalaya, could see the river approach flood stage in a few weeks.
“It’s nothing that’s abnormal other than typically we don’t get it this late in the summer. It’s typically more April and May,” Graschel said.
Ricky Boyett, spokesman for the Corps’ New Orleans District, said higher water in the Atchafalaya could lead to phase one flood fight procedures, which means the Corps will inspect levees. He added the phase one flood fight is nearly an annual occurrence for the Corps on the lower Mississippi and in the Atchafalaya Basin.
Follow David J. Mitchell on Twitter, @NewsieDave.