The Corps’ Mississippi Valley New Orleans (MVN) expects to open an additional 5 bays of the Bonnet Carré Spillway today (April 8, 2020) in order to ensure the maximum flow at New Orleans 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 and 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 1,307,000 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 45 bays and by the end of the day the forecast flow with a total of 50 bays open indicates that approximately 50,000 cfs will be diverted from the Mississippi River and into Lake Pontchartrain via the floodway. The flood control structure has total of 350 bays and approximately 100 bays are expected to be opened to pass this flood.
The Mississippi River forecast shows a gradual increase in flow up to the dates of the projected crest (maximum flow) from April 11th to April 12th. The latest forecasts predict the flow through the flood control structure will be approximately 80,000 cfs for this opening, with an overall duration of approximately 3-4 weeks.
BONNET CARRÉ SPILLWAY OPERATION 2020
|DATE||CARROLTON GAUGE (NEW ORLEANS)||DAILY NUMBER OF BAYS OPENED||TOTAL NUMBER OF BAYS OPENED||SPILLWAY DISCHARGE CUBIC FEET PER SECOND (cfs)|
|4/3/20||16.30 feet||10||10||16,000 cfs|
|4/4/20||16.38 feet||0||10||16,000 cfs|
|4/5/20||16.60 feet||0||10||16,000 cfs|
|4/6/20||16.70 feet||10||20||24,700 cfs|
|4/7/20||16.75 feet||25||45||48,000 cfs|
|4/8/20||16.70 feet||5||50||50,000 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:
“The crest on the lower Mississippi River is near Arkansas City, AR today. Rises of another 1/2 foot will continue downstream through the weekend.
Significant falls are occurring on the lower Ohio River and those falls should reach New Orleans by late April.
The 16 day future rainfall guidance continues to show a smaller secondary rise for late April. This would only slow the recessions on the lower Mississippi River.”
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.”