Take Down: West Fork Mouth Bar

DRC (Disaster Recovery Corporation) excavators are slowly whittling down the mouth bar of the West Fork of the San Jacinto. DRC is picking up where the Army Corps and Great Lakes Dredge and Dock left off around Labor Day last year. The Corps and Great Lakes removed 500,000 cubic yards of sediment. DRC will remove another 400,000 in 8-12 months as part of its contract.

DRC Focus Differs from Corps’ So Far

The Corps effort focused on deepening the channel between the mouth bar and Atascocita Point. DRC’s effort appears to focus on reducing the mouth bar itself.

A survey conducted after the Corps finished in September showed they had reduced the average depth in front of the mouth bar to about 5.5 feet. Local residents including high-level geologists questioned whether that was enough to restore safety. They pointed out that the river upstream of the mouth bar had been dredged to more than 25 feet and worried that the 20 feet difference would partially dam the river during floods and create a backwater effect that contributed to flooding.

But instead of deepening the channel, the next phase of dredging seems aimed at reducing the mouth bar itself.

Progress to Date in Reducing Mouth Bar

Aerial photos taken on 2/13/2020, show that to date DRC has removed most vegetation from the bar. They have also reduced the crown of the bar and flattened it to create a platform for excavator(s) that’s little more than a foot or so above the water. Parts of the bar used to stand four to five feet above water.

While two excavators worked on the scalping process Thursday, a third took bites from the edge of the bar, much like a human might nibble away at an ear of corn, row by row.

On Thursday, 2/13/2020, three excavators worked various portions of the mouth bar.
Two were still leveling the bar and removing vegetation while a third whittled down the edges of the bar.
The excavator near the water appears to be walking backward as it pulls sediment from in front of it and dumps it on the waiting pontoon.
When the pontoon is full, a small tug pushes it upstream.

Placement Area for Sediment

Tugs push the pontoons upstream to Berry Madden’s property on the south side of the West Fork, just upstream from Kings Lake Estates, roughly opposite River Grove Park.

…through the back channels of the West Fork to Berry Madden’s property, the placement area. Photo courtesy of Josh Alberson.
At Madden’s property, the sediment is offloaded. Photo courtesy of Josh Alberson.
The tug will then take a pontoon back downstream for the next load.
The sediment will then get loaded into dump trucks…
…and carried away from the river.

From the number of trucks on Madden’s property, it appears that DRC is using it as its command post for the operation.

Bulldozers then compact the dirt and spread it out.

Operational Tempo Expected to Increase

Josh Alberson, a local boater, monitors the dredging program. He says that the cycle time per pontoon load has decreased from roughly three hours to about two hours and twenty minutes.

Berry Madden, the placement area owner, says DRC has told him that it expects to add more equipment to the job by next week. That should increase the operational tempo and the volume of sediment transported each day.

Madden’s property is also permitted to receive spoils from hydraulic dredging.

The Harris County Engineering Department is managing this project with the City of Houston.

Next Steps Still Unclear

The Harris County Engineers office has not yet released plans for the remainder of the project. Several things remain unclear at this point. Key among them:

  • Why remove the mouth bar instead of deepening the channel in front of it?
  • Will the operation switch over to hydraulic dredging to speed up the project and reduce the flood-risk window?
  • What will the next steps be after completion of the West Fork?
  • Have the partners agreed on a maintenance dredging program?

The grant request submitted by the County to the TWDB indicates that the team also expects to tackle the rapidly growing East Fork mouth bar. During Imelda, boaters say the channel north of Luce Bayou silted in badly. It went from 18 feet deep to approximately 3 at the deepest point, they say.

Posted by Bob Rehak on 2/15/2020 with photos from Josh Alberson

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