The Corps’ Mississippi Valley New Orleans (MVN) continued closing operations and closed an additional 10 bays on the Bonnet Carré Spillway. The MVN expects to slowly close the structure until all bays are closed. The bays are operated to manage the maximum flow at New Orleans and ensure it does not exceed the target flow of 1.25 million cubic feet per second (cfs). The Spillway’s operation is based on the estimated flow at Red River Landing which is utilized to manage the number of bays opened to ensure the flow of 1.25 million cfs is not exceeded below the flood control structure. The estimated flow at Red River Landing today is reported to be 1,220,000 cfs.
The Bonnet Carre´ Spillway is a flood control structure extending from Mile 128.8 Above Head of Passes to Mile 127.3 Above Head of Passes that is designed to pass flood water from the Mississippi River into Lake Pontchartrain to prevent flooding below the Spillway.
The MVN had previously opened 90 bays and has now closed 40 bays, the forecast flow with a total of 50 bays open is now estimated to be 43,000 cfs which is being diverted from the Mississippi River and into Lake Pontchartrain via the floodway. The flood control structure has a total of 350 bays and just over one-quarter of the bays were opened to pass these flood waters.
The Mississippi River forecast indicates a gradual and slow decrease in flow through the second week of May. The maximum flow through the flood control structure for this opening is expected to remain the 90,000 cfs. The MVN anticipates closing the structure slowly based on forecasted stages and flows. The flood control structure’s operation will have a duration of approximately 29 days, with full closure expected on May 1, 2020.
BONNET CARRÉ SPILLWAY OPERATION 2020
|DATE||CARROLLTON GAUGE (NEW ORLEANS)||DAILY NUMBER OF BAYS OPENED||DAILY NUMBER OF BAYS CLOSED||TOTAL NUMBER OF BAYS OPENED||SPILLWAY DISCHARGE CUBIC FEET PER SECOND (CFS)|
|4/3/20||16.30 feet||10||N/A||10||16,000 cfs|
|4/4/20||16.38 feet||0||N/A||10||16,000 cfs|
|4/5/20||16.60 feet||0||N/A||10||16,000 cfs|
|4/6/20||16.70 feet||10||N/A||20||24,700 cfs|
|4/7/20||16.75 feet||25||N/A||45||48,000 cfs|
|4/8/20||16.70 feet||5||N/A||50||50,000 cfs|
|4/9/20||16.70 feet||20||N/A||70||63,000 cfs|
|4/10/20||16.80 feet||20||N/A||90||76,000 cfs|
|4/11/20||16.90 feet||N/A||N/A||90||76,000 cfs|
|4/12/20||17.00 feet||N/A||N/A||90||80,000 cfs|
|4/13/20||17.10 feet||N/A||10||80||80,000 cfs|
|4/14/20||17.15 feet||N/A||0||80||81,000 cfs|
|4/15/20||17.30 feet||N/A||0||80||76,000 cfs|
|4/16/20||17.30 feet||N/A||0||80||90,000 cfs|
|4/17/20||17.30 feet||N/A||0||80||90,000 cfs|
|4/18/20||17.30 feet||N/A||0||80||88,000 cfs|
|4/19/20||17.30 feet||N/A||0||80||84,000 cfs|
|4/20/20||17.10 feet||N/A||0||80||83,000 cfs|
|4/21/20||17.10 feet||N/A||0||80||77,000 cfs|
|4/22/20||17.10 feet||N/A||0||80||74,000 cfs|
|4/23/20||16.90 feet||N/A||0||80||71,000 cfs|
|4/24/20||16.90 feet||N/A||10||70||60,500 cfs|
|4/25/20||16.84 feet||N/A||10||60||54,000 cfs|
|4/26/20||16.80 feet||N/A||10||50||43,000 cfs|
A forecast update provided by our colleagues from the National Oceanic and Atmospheric Administration’s (NOAA) Lower Mississippi River Forecast Center is attached, highlights from this update specific to the New Orleans are reproduced below:
“ On the lower Mississippi River, major flooding will continue at Baton Rouge, LA for the next couple of weeks. Other locations will continue to have minor to moderate flooding through most of May. Impacts are mainly to agriculture and navigation.
The lower Mississippi River is cresting from Osceola, AR downstream to Helena, AR. Over the next 5 days, falls of 1 to 3 feet will occur from New Madrid, MO to Helena, AR and falls of ½ foot or less can be expected from Arkansas City, AR to New Orleans, LA.
The 16 day future rainfall guidance shows a secondary rise on the lower Ohio River which will keep Cairo, IL above flood stage through mid May. This secondary rise will only slow recessions on the lower Mississippi River and extend the flooding for a couple of more weeks.”
The Bonnet Carré Anchorage was closed by the U.S. Coast Guard at 6:00 a.m. on April 3, 2020, vessels shall not enter the anchorage or the area extending 600 feet into the river from the Bonnet Carré Spillway, between MM 127 and MM 129 and the shoreline of Lake Pontchartrain.
“MARINERS ARE ADVISED THAT THE M/V KENT WILL BE STATIONED ON THE LEFT DESCENDING BANK JUST NORTH OF THE SPILLWAY TO MONITOR MARINE TRAFFIC ON VHF MARINE CHANNELS 16 AND 67. SHOULD AN INCIDENT OCCUR BETWEEN THE SPILLWAY AND MISSISSIPPI RIVER MILE 140 ABOVE HEAD OF PASSES (AHP) INVOLVING AN ADRIFT VESSEL, BARGE, ETC., THE ATTENDING VESSEL OR ANY OTHER VESSEL IN THE VICINITY SHOULD IMMEDIATELY REPORT THE INCIDENT TO THE M/V KENT.”