Based on reduced flows in the Mississippi River at Red River Landing, the U.S. Army Corps of Engineers, New Orleans District has begun the closure of bays at the Morganza Floodway. Currently, the structure has 14 bays open with a discharge rate of 140,000 CFS. One bay was closed yesterday evening and two more bays were closed this afternoon.
Since the opening the Morganza Floodway on May 14th, discharge into Morganza Floodway has been reported daily. The Corps computed the discharge, in cubic feet per second, through the structure. Beginning on May 18th, discharge measurements were taken onsite by our federal partners at United States Geological Survey (USGS) to validate the computed measurements. A significant difference in the computed and measured discharge rates was discovered. After a review of this difference, it was determined that the computed flow understated the discharge from the Morganza Floodway.
“Thanks to our strong partnership with the USGS, we have better tools to make decisions based on the best science and modeling efforts available,” says Ken Holder, Chief, Public Affairs Office. “In addition, water levels continue to be lower than anticipated throughout the Atchafalaya Basin.”
Working closely with our partners at USGS, we have determined the Morganza Floodway was discharging at a rate of 172,000 CFS with 17 bays open, well below our initial estimates of 300,000 CFS, instead of the reported 114,000 CFS. This discharge of 172,000 CFS is well within the water control plan for the structure, which is designed for a 600,000 CFS capacity. The discharge measurement has no effect on gate operations at the Morganza Floodway.
The inundation maps were initially developed to reflect 50 percent operation of the Morganza Floodway and based upon a discharge rate of 300,000 CFS. Modified inundation maps reflect a Morganza Floodway discharge rate of 150,000 CFS, with 25 percent operation of the structure.
Operation of the structure is based on flow rates in the Mississippi River at Red River Landing and water stages at the Morganza Floodway structure itself. The Corps will continue to assess conditions for the Mississippi River and operate the Morganza Floodway and Bonnet Carre Spillway in the interest of public safety. The Corps will remain vigilant during this extended flood fight and will continue to assess water levels and conditions in the Atchafalaya Basin.