Ascension Parish workers cut a small channel across Alligator Bayou Road, speeding up the drainage of high water into Bayou Manchac and away from surrounded homes in the Bluff Swamp area.

Parish officials said the cut across the road where Fish Bayou meets Bayou Manchac in the northwestern corner of the parish was finished Friday.

The high water, which has been as deep as 11 feet in some areas, is the remnant of a heavy rainstorm on May 17 and May 18 that had its most intense rainfall focused on south Baton Rouge and northwestern Ascension. 

A rain gauge at Alligator Bayou and Bayou Manchac recorded 13.04 inches through the morning of May 18, though the bulk of that rain fell in about six to eight hours, National Weather Service data show. 

Creeks and rivers that flow into Manchac from East Baton Rouge Parish were quickly swollen with the heavy rains and met high water also in the bayou and the swamp.

Alligator Bayou Road rests on a levee along the south bank of Bayou Manchac, and, with the exception of a few floodgates, holds back water in the Bluff Swamp and the greater Spanish Lake area covering a combined 17,000 acres.

Once high water builds up in the bowl-shaped lowland swamp forest, it can take days to weeks for it drain without additional help, parish officials have said.

But the levee road also only goes so high.

Earlier this month, Iberville Parish officials installed portable water-filled AquaDams on top of Alligator Bayou and Manchac roads.

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The dams, which extend into Ascension Parish, were intended to prevent high water in Bayou Manchac from flowing back over the levee roads into the swamp basin. 

Iberville officials won a court fight with Baton Rouge officials to keep the dams in place. East Baton Rouge officials have contended the dams could worsen flooding for their residents on the north side of the bayou.

Ascension and Iberville parish officials had tried a similar tactic to remove water from the swamp basin after the August 2016 flood. Multiple roads cuts tried then also shut Alligator Bayou and Manchac roads for an extended period of time.

They both remained closed Saturday.

Ron Savoy, the Ascension public works director, said that, in addition to the road cut, crews were operating seven pumps to move water out of the basin: four 30-inch axle driven pumps and three 24-inch tractor pumps. 

Parish Councilwoman Teri Casso, who represents the residents in the Bluff Swamp area, said the effect of the road cut was already being felt late Friday with water levels starting to ebb. 

In a statement, Ascension Parish President Clint Cointment described Friday's actions as a “significant event on a dramatic day” and acknowledged the dedication and commitment of parish public works employees.

Hurricane season begins Tuesday.


Email David J. Mitchell at dmitchell@theadvocate.com

Follow David J. Mitchell on Twitter, @NewsieDave.

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