The latest update issued to the Mississippi River Commission (MRC) as the Mississippi Valley Weather & River Report 2/22/2018 is attached.
The Corps’ Mississippi Valley New Orleans (MVN) began opening bays on the BonnetCarré Spillway earlier today (Wednesday, February 27, 2019). The MVN planned to open 28 bays in order to keep the maximum flow at New Orleans at or below the target flow of 1.25 million cubic feet per second. A rough estimate is that the 28 bays would divert about 25,000 cubic feet per second from the Mississippi River and into Lake Pontchartrain via the floodway.
On February 25, 2019, Major General Richard G. Kaiser, the President of the Mississippi River Commission and Commander of the USACE Mississippi Valley Division (MVD – Vicksburg), granted Colonel Michael Clancy the District Commander for MVN the authorization to operate the Spillway in accordance with the approved Water Control Manual and MVD Operations Plan for Floods (Recommendation is attached). Colonel Clancy indicated that approximately 200 bays may eventually be opened and that the structure could be operated for a month or so based on efforts to maintain the maximum flow at New Orleans.
BONNET CARRé SPILLWAY OPERATION
| Date | Carrollton Gauge (New Orleans) | Bays Opened | Total Number of Open Bays | Spillway Discharge Cubic Feet Per Second (cfs) |
| 2/27/19 | 16.02 feet | 28 | 28 | 25,000 cfs (estimated) |
The map below highlights that the majority of the Mississippi River and Tributaries is wetter than it has been in 124 years. The map represents measured regional precipitation from August 2018 to January 2019 and ranks much of the basin as the wettest is has been since 1895 (124 years). The river stages have accordingly remained elevated above 10 feet on the Carrolton Gauge since November 2018. The Carrolton Gauge is now expected to reach 17 feet on March 6, 2019 and to remain at that stage for about three weeks with the Bonnet Carré Spillway operation expected to hold the crest at that level.
Update to Mississippi River Commission Mississippi Valley Weather & River Report 2/22/2019
Summary:
As the second expected system this week has begun to move through Valley, actual rainfall amounts have continue to exceed forecasted amounts. Based on the water on the ground today, and expected rainfall through Saturday forecasted stages were raised throughout the Lower Mississippi River. Official forecast now has Cairo peaking at 56.5’ on March 2nd. All current forecasted peaks and dates are shown in Figure 7 below.
This rise in the Cairo forecast is partly due to the need to continue releases at Kentucky-Barkley in order to contain storage because of the uncertainty of the remainder of this event and the ability to mitigate future rainfall. This forecast may need to be adjusted slightly as this weekend event is hitting the ground, however there is high confidence that we still have the reservoir capacity to mitigate this peak well below potential activation stage at Birds Point New Madrid Floodway. While we do not anticipate operation of the floodway at this time, this Saturday and Sunday will be critical days as leadership continues necessary discussions for staging & preparations should there be a need.
With an expected reprieve from rainfall after this weekend systems passes, for most of the watershed through 5-March, LRD will be working to evacuate flood storage from Kentucky and Barkley reservoirs. Cairo will retain a broad crest of around 56.5′ for 7-8 days. Figure 1 below shows Kentucky reservoir current pool elevation, which will increase to the range of 364-365′ with the associated 56.5′ crest, utilizing approximately 50% of the combined flood storage available at Kentucky & Barkley. While 56.5′ will be the 3rd highest crest ever seen at Cairo (See Figure 2), this will be a controlled (regulated) outcome where MVD and LRD will be proactively evacuating flood storage to ready ourselves for future rainfall expected beyond 5-March. During this period, we expect to lower the Kentucky & Barkley pools by approximately five feet.
Within the Vicksburg District, the Yazoo River Basin reservoirs are utilizing significant flood storage, but are expected to remain well below spillway elevations for all 4 lakes. However located at the lower end of the basin, the Steele Bayou structure will need to remain closed for several weeks to keep the main stem MS River from backing in. This will result in interior stages in the Yazoo Back Area to rise. Yazoo Backwater Area (encompassing the land between the levees between the mainstem Mississippi and Yazoo Rivers) will see dramatic stage increases in the range of 96′-97′. This will be the highest stages experienced in this area since 1983. Seeing Figure 3 below, you can see the large amount of inundated area from Eagle Lake above Vicksburg up to Greenwood, MS.
The increased stages also forecast Red River Landing going to 61. That equates to approximately a 58.5′ stage and 1.48 million cfs flow at Morganza Floodway. Morganza Floodways is utilized when we anticipate flows to exceed 1.5 million cfs on a continued rising hydrograph. We do not anticipate the need in operating Morganza at this time. However, we will be continuing to monitor flows, stages, and conditions in this area.
Bonnet Carre’ is now anticipated to be opening on approximately Wednesday 27-Feb to prevent the flow in New Orleans from exceeding 1.25 million cfs.
Figure 4 and 5 below show the rainfall for the past 24 hours and 14 days respectively. Figure 6 indicates the remaining precipitation we expect to see this weekend. Other info on tributaries and hydrographs at critical areas on the MS River follow.
Again, this Saturday/Sunday are critical days as we continue to monitor this weekend’s event.
MEMORANDUM FOR Commander, New Orleans District
Recommended Operation of the Bonnet Carre Spillway
SUBJECT: Recommended Operation of the Bonnet Carre Spillway
1. Reference memorandum, CEMVN-DE, to President, Mississippi River Commission and Commander, Mississippi Valley Division, 25 February 2019, subject as above.
2. Based on current and predicted stage and discharge hydrographs, I concur in your recommendation for operation of the Bonnet Carre Spillway in accordance with the approved Water Control Manual and the Mississippi Valley Division Operations Plan for Floods. It is noted that the recommended latitude in spillway operation is a practical necessity due to the inability to precisely measure river flows or precisely control the spillway discharge.
3. You have approval to initiate operation of the Bonnet Carre Spillway on 27 February 2019 in order to not exceed 1.25 million cfs. Please provide me your schedule for initiating operation of the spillway. If life, health, and/or safety circumstances arise that indicate a need to alter this operation date, please inform me and I may adjust it depending on the circumstances.
