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Dewberry presents Amite River Basin master plan draft; warns of higher 2050 flood risks and recommends remapping and freeboard standards
Summary
Dewberry told the ARBC that modeling to 2050 projects increased sedimentation and higher flood elevations that could place thousands more structures in the floodplain; the consultant recommended higher freeboard, FEMA map updates using LWI data, and Community Rating System steps to lower insurance costs.
Consultant Sam Kampton of Dewberry told the Amite River Basin Drainage and Water Conservation District on Dec. 10 that its draft master plan models to 2050 show substantial sedimentation and flood‑risk increases if no action is taken.
Kampton said simulations project 1–7 feet of additional sediment adjacent to the weir and estimated about $777 million in additional 100‑year flood losses by 2050 in today’s dollars. He said the scenario would place nearly 8,000 additional structures into the floodplain unless communities adopt higher regulatory standards such as increased freeboard for new and substantially improved residential structures.
Kampton described a hypothetical: if a 1‑foot freeboard had been implemented earlier, the region would have avoided roughly $11.2 million in average annualized losses for about 4,000 residential structures identified in the National Structure Inventory. He also urged using Louisiana Watershed Initiative (LWI) data and lidar‑based elevation models to update FEMA flood maps so that many communities could be remapped more accurately.
Commissioners discussed insurance and mapping benefits. Commissioner O'Neil highlighted two paths to lower homeowner premiums: (1) improving Community Rating System (CRS) participation to gain discounts, and (2) remapping to remove properties incorrectly included in special flood hazard areas. A commissioner referenced Dewberry modeling that—if adopted into FEMA maps—could remove as many as 13,000 people from the mandatory purchase requirement, a change that could substantially reduce annual costs for affected households.
The consultant said the draft plan will be delivered to the board on Dec. 30, 2024, with some project details to be merged in January; public meetings to present and gather feedback on the draft will be scheduled after the delivery and coordinated with the board.
Next steps: Dewberry will provide parish‑level appendices and the board asked staff to pursue CRS and remapping data (including DOTD/DOT floodplain manager input) as part of outreach and plan implementation.
