The Corps’ Mississippi Valley New Orleans (MVN) expects to open an additional 20 bays of the Bonnet Carré Spillway today (April 10, 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 1,313,000 cfs (unchanged from 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 70 bays and by the end of the day the forecast flow with a total of 90 bays open indicates that approximately 76,000 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 indicates a gradual increase in flow up to the projected crest date of April 12th. As of today’s forecast estimates are nearing the maximum predicted flow through the structure, maximum flow diverted 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. This could be the maximum number of bays opened, 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)
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.”