Atchafalaya expected to rise to 8 feet

While local emergency preparedness officials have been working on COVID-19 precautions, another source of concern has been coming down the river.
The Atchafalaya River at Morgan City topped the 7.0-foot moderate flood stage overnight, reaching 7.11 feet by 6 a.m. Tuesday. The National Weather Service says the river will reach 8.0 feet Friday or Saturday.
But that doesn’t mean Morgan City and lower St. Martin are in for major flooding, much less a repeat of last year’s long-lasting flood event.
St. Mary Parish Levee District Director Tim Matte said the Mississippi River, the stage of which determines what happens with the Atchafalaya, is cresting to the north, and the crest is moving south. He said predictions are for an Atchafalaya crest around April 16.
Additional flood wall gates may have to be closed in Morgan City and Berwick, and Stephensville residents could see more street flooding.
On Friday, the U.S. Army Corps of Engineers planned to open 10-20 of the 350 gates in the Bonnet Carré Spillway, diverting water from the Mississippi into Lake Pontchartrain. The move came in response to a sudden increase in the predicted crest of the Mississippi at New Orleans, reaching the 1.25 million cubic feet per second flow that the Corps calls an “operational trigger.”
The Mississippi at the Carrollton Street gauge in New Orleans was at 16.78 feet at 6 a.m. Tuesday and is expected to hit the 17.0-foot minor flood stage Wednesday. The National Weather Service forecast is for the river to stay at 17 feet until about April 16, then start falling.
The opening of the Bonnet Carré by itself doesn’t mean anything for the Atchafalaya other than the river is high, Matte said.
Last year the Atchafalaya hit 18.25 feet in March and stayed until mid-summer. A temporary flood control structure, a sunken barge, was placed in the Bayou Chene to ease the back-flooding that afflicts lower St. Mary and surrounding areas when the river is high.
That led to approval of funding for an $80 million permanent flood gate that is now under construction.
The COVID-19 pandemic has had an effect even on that work. Matte said the district has given bidders for the contract to do the major part of the work more time because some have had trouble connecting with potential subcontractors and suppliers.
Bayou Chene also has an impact on flooding along Lake Palourde. The stage there at 6 a.m. Tuesday was 4.67 feet, above the 4.0-foot “action level” but below the 5.0-foot minor flood stage.
Friday’s Bonnet Carré opening came despite requests from Mississippi officials, who say the Corps should consider opening the Morganza Floodway as an alternative to the Bonnet Carré.
Officials in Mississippi have sued the Corps and the Mississippi River Commission, saying the frequent openings of the spillway, which sends water to that state’s coast, causes flooding there and damages the seafood industry.
But Col. Stephen Murphy of the Corps said Friday that sending more water into the Atchafalaya would put more pressure on the Morgan City area and be potentially “devastating.”