The Corps’ Mississippi Valley New Orleans (MVN) expects to open an additional 25 bays of the Bonnet Carré Spillway today (April 7, 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 estimated flow at Red River Landing is the one 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 1,296,000 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 20 bays and by the end of the day the forecast flow with a total of 45 bays open indicates that approximately 46,700 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 12th to April 13th. 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 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||47,000 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 Bonnet Carré Floodway continues to operate and reduce flow at New Orleans, LA. This will cause New Orleans, LA and Reserve, LA to crest before upstream locations. New Orleans, LA will crest at the 17.0ft flood stage on Wednesday, April 8th and will stay near this level for the next 1 ½ weeks. The floodway has been operated for 3 years in a row and 4 of the last 5 years
The 16 day future rainfall guidance is showing a secondary crest on the lower Ohio River for late April. This crest would be 10 feet lower than the current crest and it would only slow recessions on the lower Mississippi River for early May.”
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.”