Steve Hardy / The Advocate
23 May 2019

State and federal officials said Thursday it was appearing more likely that the U.S. Army Corps of Engineers would need to open the Morganza Spillway next month — for only the third time ever — to stave off what one likened to a “foreign disaster” flowing Louisiana’s way.

It is now “more likely than not that the Morganza Spillway will be opened” June 2, Louisiana Gov. John Bel Edwards announced Thursday afternoon. U.S. Rep. Garret Graves said it appeared most believe that opening the 65-year-old spillway is inevitable.

“There seems to be little doubt of crossing the threshold,” said Graves, a Republican from Baton Rouge.

The Mississippi River has been at or above flood stage for a record number of days in much of south Louisiana, and the Bonnet Carré spillway has been opened twice this year for the first time in history.

Opening the Morganza would send river water through a structure in Pointe Coupee Parish, then on through the Atchafalaya Basin toward Morgan City and finally into the Gulf of Mexico, relieving some of the strain on Mississippi River levees downstream.

Louisiana and local officials are trying to evacuate people and livestock from the spillway, move heavy equipment and make sure to batten down oil and gas infrastructure throughout the basin.

Still, the Corps isn’t completely sure it will open the spillway, and doesn’t expect to make a decision until Tuesday. Edwards said the Corps will make the call based on the river’s level and flow. Corps spokesman Ricky Boyett said engineers are waiting to see how much rain falls upstream in the next few days.

Edwards held a press conference on the Morganza after meeting with leaders from agencies such as the Corps, the Department of Transportation and Development, the Coastal Protection and Restoration Authority, the state fire marshal, the Red Cross, the Coast Guard and the state departments of Wildlife and Fisheries as well as Agriculture and Forestry.

The Corps is expected to produce inundation maps indicating water depths should the Morganza open, but they were not completed by Thursday. Officials were notsure how many structures could be at risk. Col. Michael Clancy of the New Orleans Corps district said the inundation maps will dictate how to proceed, and whether to take certain action such as sinking a barge along Bayou Chene to divert floodwaters.

The state will request federal aid to help pay for flood-fighting equipment such as the barge, sandbags and other material if the spillway opens, Edwards said. The state could possibly ask for individual assistance for affected property owners if needed down the line, he continued.

Graves pointed out that most of the water flowing through Louisiana originated somewhere else.

“It’s sort of a foreign disaster that comes to us,” the congressman said.

Clancy acknowledged that the inundation maps released ahead of the 2011 spillway opening did not turn out to be accurate. Flooding wound up being much less severe than advertised.

Graves said the Corps’s topographical information was incorrect, and engineers made some faulty assumptions about how much water would be absorbed into the dry ground. The Corps has “greatly improved” its models since, Clancy promised. Unlike the 2011 event, when the Atchafalaya was in drought, this year that river is high.

If the Corps uses the Morganza Spillway this year, it will perform a slow release, Edwards said.

Corps officials have said the water could overtop the spillway structure on June 5, making it less safe to open.

Mississippi River water is held back by giant doors in a concrete wall. The Corps would plan to start opening the bay doors June 2, opening one per day for the first three days. That would allow the water level to rise 1 foot per day for those first three days, giving wildlife a chance to escape, the Corps has said. After the initial three days, the Corps could open more of the structure’s 125 gates.

In addition to the animals and people, authorities are trying to make sure oil and gas infrastructure is ready to ride out the water. That includes precautions like making sure oil tanks are weighed down with water, that well heads are shut off and marked so they don’t get hit by boats and that any chemicals are removed from the spillway, Louisiana Natural Resources spokesman Patrick Courreges said.

He said Louisiana workers are used to the protocol, and Louisiana Mid-Continent Oil and Gas Association President Tyler Gray said his members’ assets were either protected or out of harm’s way.

Each time Morganza opens, it gets a little less effective, warned Robert Twilley, director of the Louisiana Sea Grant Program. The Mississippi River carries sediment that is deposited along the spillway, filling it in a bit with each use. That can be useful restoring coastal areas lost to subsidence, but it can also turn Atchafalaya wetlands into uplands, Twilley said.

It’s easy to clean up the short spillway between the Bonnet Carré gates and Lake Pontchartrain, but there is a massive amount of land between Morganza and the Gulf where it would be impossible to remove all the deposited sediment, he continued.

More broadly, the “truly unprecedented” possibility of two Bonnet Carré openings and a Morganza opening in one year speaks to the effects of climate change, said John Lopez, who spoke on behalf of the Restore the Mississippi River Delta environmental coalition. The river is so high because of increasing precipitation in the watershed and more instances of massive deluges, he continued.

https://www.theadvocate.com/baton_rouge/news/environment/article_e9b1e66e-7d65-11e9-9e0b-eff710bb4332.html