New Orleans Still Awaits Lower Miss Flood Crest

The Lower Mississippi River remained dangerously high last week, with the Carrollton gage in New Orleans hovering at about 16.5 feet. But the river stage and flow rate through the New Orleans area had actually fallen off by week’s end, thanks to the operation of the Bonnet Carré Spillway.

By March 15, the Carrollton gage read 16.4 feet, down from a high point of 16.68, and the flow rate below the city was close to about 1.1 million cubic feet per second (cfs). Earlier last week, the flow rate near Belle Chasse, La., downriver from New Orleans, came close to hitting 1.3 million cfs.

The U.S. Army Corps of Engineers began opening bays at the Bonnet Carré Spillway on March 8. Two days later, just 29 bays were open, with about 26,000 cfs. diverted toward Lake Pontchartrain. But beginning March 11, the Corps drastically increased the bays opened at the spillway. By March 13, 148 bays had been opened, diverting 141,000 cfs. from the Mississippi River toward the lake. The Corps did not open any addition bays March 14, and the discharge on that day had actually dropped a bit. By March 15, the Corps reportedly had opened 20 more bays, bringing the total to 168 bays opened and a discharge of 155,000 cfs.

The U.S. Weather Service still called for the Mississippi River in New Orleans to hit 17 feet at the Carrollton gage this past weekend and stay there until around March 27.

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Farther upriver, the Old River Lock, located on the Mississippi River just above the Red River Landing, was slated to close to navigation March 15 in anticipation of the gage at the Red River Landing reaching 60.5 feet. Forecasts there called for the lock to remain closed until about March 24.

Last week, water levels on the Red River had already dropped, allowing all five locks on that system to open to navigation The Corps surveyed the Red last week in order to identify problem areas for shoaling.

Locks leading to the Atchafalaya River and the Port Allen Route between the Mississippi River and the Gulf Intracoastal Waterway (GIWW) remained open to navigation, with the exception of Bayou Boeuf Lock, which has been closed due to gate repairs and a high head differential.

Farther south in Morgan City, La., the Coast Guard is requiring tows greater than 400 feet to have an assist vessel when passing through the bridges. The Atchafalaya River in Morgan City is expected to crest at about 8 feet on March 23.