A flood warning for New Orleans will take effect Jan. 12 when the Mississippi River is expected to reach its 17’ stage there – posing only a minor flooding threat to the city but with new restrictions on navigation likely.
Near-historic crests were observed last week on the Illinois River and parts of the upper Mississippi, although concerns eased somewhat as crests fell. Still, the levels moving downstream portend weeks of fast water, similar to conditions that contributed to allisions, runaway barges and capsizings last spring and summer.
The Army Corps of Engineers opened gates at the Old River Control structures, 50 miles northwest of Baton Rouge, La., in anticipation of pressure from the rising river. With the Atchafalaya River in line to get its designated 30% of flow via Old River, the Coast Guard imposed high-water towing limitations on southbound vessels near Morgan City, La. To the north, the Coast Guard reopened parts of the Mississippi, Illinois and Ohio rivers, albeit with warnings and restrictions on transport operations.
In one sign of easing pressure, the Corps’ Memphis District said lowered river forecasts led them to hold off plans to open the Birds Point-New Madrid floodway. District commander Col. Jeff Anderson said “it doesn’t mean we’re completely out of the woods.”
“While this ends planning and preparation for this event, we must remain vigilant for any other events that may happen this flood season,” Anderson said Tuesday, as the weather service called for a 44’ crest at New Madrid, Mo., 14’ over flood stage. “There’s still a lot of water in the system that’s making its way to the Gulf of Mexico and we must be prepared for future rain events within the massive Mississippi River drainage basin.”
Col. Rick Hansen, commander Corps of Engineers New Orleans District, talks about plans to open Bonnet Carré at a press conference on Jan.5, 2016. USACE photo.Near New Orleans – where high water is not expected to top the levees, but could make navigation difficult – the Corps prepared for opening the Bonnet Carré and Morganza spillways by mid-January — with Bonnet Carré potentially opening as soon as Saturday — based on forecasted river stages.
At the 17’ stage the city is still protected by 3’ to 5’ of additional freeboard from flood gates and walls in addition to the levees. But even at the 14’ stage now being observed, “strong eddies will develop below the gage at Carrollton, with increased negative impacts on navigation,” the National Weather Service said in an advisory issued Tuesday.
High and fast water last spring and summer contributed to a string of accidents, some with fatalities, and led the Coast Guard and Corps of Engineers to issue warnings and traffic controls. All that flow brought a lot of sediment down to the lower river, and in August the Associated Branch Pilots of the Port of New Orleans began to require time and tide restrictions for moving deeper draft vessels.
The weather service blamed an abundance of rain — up to an extra 10” to 15” over parts of the upper Mississippi and Ohio River watersheds — on a strong El Niño, the band of warm Pacific currents that can send big weather systems east across the continental U.S.
