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Dewberry reports field reconnaissance, sediment findings and options in ARBC master plan update
Summary
Dewberry told the Amite River Basin Commission it completed August field reconnaissance and about 92 sediment samples, identified upstream erosion and downstream deposition patterns, and urged targeted dredging and upstream detention as priority actions while public outreach continues.
Dewberry consultant Sam Campton told the Amite River Basin Commission that a August field reconnaissance and sediment sampling program has begun to shape the regional master plan.
"We did a good bit of field reconnaissance," Campton said, describing boat-based surveys, sonar and sediment coring that produced about 92 samples. He said the team found active bank erosion upstream of the diversion weir and a downstream reach dominated by "clay muck" deposits, while sand began appearing near Port Vincent.
Campton said the pattern suggests a sand wedge moving downstream and identified dredging in the diversion vicinity as a leading candidate for near-term work. "In my professional opinion, this is gonna be the most bang for the buck with dredging," he said.
The consultant outlined about 15 candidate projects being evaluated for short- and long-term benefits, including an integrated basin model, a river pump-station concept and detention locations upstream and downstream. Campton said modeling is being updated to include the diversion structure and to run a "phase 2 baseline" that captures current conditions plus imminent projects.
Garvin Pittman, the Region 9 coordinator for the Louisiana Watershed Initiative who oversees ARBC master-plan committee work, said biweekly master-plan meetings with Dewberry have been used to refine scope, review invoices and prepare CPRA reimbursement submittals. "We've held public meetings in Livingston, Ascension and Baton Rouge," Pittman said; Dewberry asked the public to use an online comment portal while staff summarized open-house feedback.
Campton added the team is also evaluating alternative detention sites, including Darlington and smaller tributary options, as ways to detain flow upstream rather than move flood risk to other reaches. He cited a recent review of future rainfall projections and said the plan will present existing-condition baselines and future-without-project scenarios, governance recommendations and funding summaries.
The presentation included outreach and habitat checks; Campton said the team did not find the targeted mussel species in sampled locations and verified sediment-sample methods by comparing clamshell grabs with spade excavations.
Board members asked that Dewberry share model files and updated deliverables with Dewberry's partners and the parish master-plan contractors. Staff and board members also noted ARBC has submitted a capital-outlay request and that region-wide funding decisions will affect how the commission divides a roughly $100 million LWI allocation for Region 9.
The commission voted later in the meeting to approve Amendment 1 to the ARBC–Dewberry contract to continue the master-plan work.
