The Corps’ Mississippi Valley New Orleans (MVN) began closing bays on the Bonnet Carré Spillway yesterday (April 13, 2020) but did not close any today. 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 1,310,000 cfs (same as yesterday).
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 closed the first 10 bays yesterday, the forecast flow with a total of 80 bays open is approximately 81,000 cfs 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 this crest.
The Mississippi River forecast indicates that the maximum flow (cresting conditions) at the structure will continue to pass between April 10th and April 17th (2020) and decreasing flows are expected after this forecasted crest. The Mississippi River forecast shows a gradual decrease in flow after this crest, which increased due to the heavy precipitation in this past weekend’s storms across the Mississippi and Ohio River valleys. A significant fall in stage/flow is forecast for the latter part of April and into May. The maximum flow through the structure for this opening thus far is 81,000 cfs. Closing of additional bays are suspended until the river starts dropping again, the estimate for overall operation is 4 weeks.
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||17.00 feet||N/A||0||80||81,000 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:
“ Rises of a few tenths are expected from Red River Landing, LA downstream to New Orleans, LA. All locations on the lower Mississippi River should be cresting by tomorrow. Cresting conditions will continue for a few days before significant falls start to approach Red River Landing, LA by late this weekend.
The Bonnet Carré Floodway continues to operate and reduce flow at New Orleans, LA. New Orleans, LA is cresting near 17.0ft and will remain at this level for the next week.
The 16 day future rainfall guidance and the official forecast using 2 days of rainfall show similar secondary crests on the lower Ohio River. This crest would only slow recessions on the lower Mississippi River from Tunica, MS downstream to New Orleans, LA.”
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.”