The Corps’ Mississippi Valley New Orleans (MVN) is not scheduled to open any additional bays of the Bonnet Carré Spillway today (April 12, 2020) 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 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 1,320,000 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 does not plan to open any today, the forecast flow with a total of 90 bays open is approximately 80,000 cfs being 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, although it may only require the 90 bays presently opened.
The Mississippi River forecast indicates that the maximum flow at the structure is expected to pass the structure today and started yesterday (April 11th and April 12th 2020) with decreasing flows expected after the crest passes. Although a strong storm system is presently moving across the Mississippi River Basin. The maximum flow diverted through the Spillway is expected to be approximately 80,000 cfs, with an overall duration of 2.5 to 4 weeks. A significant fall in stage/flow is forecast through the second half of the month. There may not be a need to open any additional bays, although the precipitation associated with this weekend’s front could change these predictions.
BONNET CARRÉ SPILLWAY OPERATION 2020
CARROLLTON 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|
|4/9/20||16.70 feet||20||70||63,000 cfs|
|4/10/20||16.80 feet||20||90||76,000 cfs|
|4/11/20||16.90 feet||0||90||76,000 cfs|
|4/12/20||17.00 feet||0||90||80,000 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 is near Vicksburg, MS today. Rises of a few tenths are expected downstream during the next couple of days. Heavy rain this weekend may add a few additional tenths to the forecast crests. Crest heights will be similar to the June 2019 event and a couple of feet higher than the February event.
The Bonnet Carré Floodway continues to operate and reduce flow at New Orleans, LA. New Orleans is forecast to rise a couple of tenths and crest at 17.0ft for Sunday, April 12th. Once it crests, it will remain near this level for the next 1 ½ weeks.
The 16 day future rainfall guidance is showing a secondary crest on the lower Ohio River that is a few feet higher than the previous forecast. This crest would be 7 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.”