The Morganza Spillway is scheduled to open June 2 as river stages swell from heavy northern rainfalls flowing into south Louisiana, the U.S. Army Corps of Engineers announced Monday.
Record-high water levels from the Arkansas River and Missouri River Valley sparked the decision, according to Ricky Boyett, a spokesman for the COE New Orleans District Office.
The opening will mark the first for the Morganza Spillway since June 2011, and only the third in its 60-year history. The COE previously opened the structure in 1973.
The spillway remained open 56 days in 1973 and 55 in 2011, according to Boyett.
The opening predicates two consecutive years the Corps opened the Bonne Carre Spillway near New Orleans. The two openings of the Bonne Carre this year marks an unprecedented move by the COE.
The Morganza announcement comes on the heels of a 214-day span of local waterways above flood stage, Boyett said.
Record rainfall – and not snow – has been the contributing factor for the high river stages for the Mississippi River and other tributaries. Forty-one percent of the nation’s waterways drain south to Louisiana, he said.
“It’s been the wettest year on the longest flood fight in our history … it’s truly a natural phenomenon,” Boyett said.
Boyett did not rule out the possibility of a change in the opening date.
“It could be sooner, but either way, we’re basically going to by what the river is doing to prevent overtopping of the structure,” he said. “So far, it doesn’t look like it will be sooner, but it’s possible.”
Current plans call for a three-day “slow opening” of a structure to minimize the deluge.
The “slow opening” comes from lessons learned in 2011.
“If we can limit the flow of water to one foot per day, that would help get the wildlife out of the floodway with the least amount of harm possible,” Boyett said
The “slow opening” would also allow time for capping of oil wells in the area and the transport of livestock from the vicinity. It would give what Boyett hopes is enough time camp owners along the floodway to take necessary precautions.
No timeframe has been set on how long the floodway will remain open.
“The river dictates the time frame, and that’s based on how long we have a risk of high water,” Boyett said. “It will all depend on what happens with the rainfall further north and what the rivers that contribute to the Mississippi River will do.”
Construction on the Morganza Spillway Project was completed in 1954. The 4,159-foot controlled spillway uses a set of flood gates to control the volume of water entering the Morganza Floodway from the Mississippi River. It consists of a concrete weir, two sluice gates, seventeen scour indicators and 125 gated openings which can allow up to 600,000 cubic feet per second of water to be diverted from the Mississippi River into the Atchafalaya Basin during major flood events.