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Amite River & Tribs - Bayou Manchac Watershed

Official Project Name
Amite River & Tributaries - Bayou Manchac, La

The study area is located in southeastern Louisiana and encompasses portions of Ascension, Iberville, and East Baton Rouge Parishes. The study area includes the entire Bayou Manchac Watershed and associated watersheds that could be used to meet project goals. This watershed-wide approach is needed to ensure sustainable benefits of the project and to resolve problems in the overall public interest. The watershed-wide approach is consistent with Corps guidance and that of other resource agencies. The study area includes Bayou Braud, Alligator Bayou, Bayou Paul, Spanish Lake, Bluff Swamp, Bayou Fountain, Dawson Creek, and Ward Creek.

The proposed actions include several alternatives that would reduce the flood stages provide ecosystem restoration benefits as an ancillary benefit.

The project is currently in the Feasibility phase and alternatives are being studied.

Benefit to the Community & Project Features

Tropical storm Allison inundated the Bayou Manchac Watershed area with over 20 inches of rain in about a week. As a consequence, some houses were flooded and many were nearly flooded. Floodwaters remained in the Spanish Lake and Bluff Swamp systems for nearly 60 days creating many problems in the basin, including mosquito problems and some negative environmental impacts. Many bottomland hardwood species cannot tolerate long-term flooded conditions during the growing season. Since Allison came in late May and early June, many larger oaks and other hardwood species were stressed and many of the younger seedlings may have been killed.


This Feasibility Study is being conducted by the U.S. Army Corps of Engineers, NOD as a continuation of the Amite River and Tributaries Initial Evaluation Study, dated November 1984. The Amite River and Tributaries Study was initiated in response to a resolution of the committee on Public Works of the United States Senate. The resolution is under the authority of the Board of Engineers for the River and Harbor Act approved on June 13, 1902. The resolution, sponsored by the late Senator Allen J. Ellender and Senator Russell B. Long of Louisiana, was adopted on April 14, 1967.


This project will be evaluated under National Economic Development (NED). The level of restoration provided by the project will be optimized according to cost effectiveness and incremental cost analysis (CE/ICA – IWR Plan). A hydraulic analysis of the Bayou Manchac Watershed and the Amite River will also be performed to determine the required elements for restoration and flood damage reduction. A benefit-to-cost analysis will be performed is any specific flood damage reduction features are pursued. Design features will be fully evaluated with respect to the latest engineering, economic, and environmental regulations for acceptability under current Federal laws and regulations. Any adverse effects of the plan that require modifications to the project will be identified. An Environmental Impact Statement (EIS) will be developed during this feasibility study. Effects on the human environment will be determined once pertinent hydraulics and design information is generated during the feasibility study. The public will be informed of the effects of the recommended actions and afforded an opportunity to comment. This public interaction will be conducted by public scoping and informational meetings and by website and email. An EIS is deemed necessary given the potential for indirect impacts associated with enclosing large tracts of undeveloped land within the protection. During the study, the Corps will determine if an Environmental Assessment is sufficient in lieu of an EIS. A first screening phase was completed in September 2002. Stakeholder meetings, PDT meetings, and preliminary hydrology and hydraulic (H&H) modeling were conducted to determine problems and opportunities. This screening document was used by the NOD PDT to develop a PMP to study these five alternatives further. The alternatives will be studied and evaluated under the NED plans as previously mentioned. This screening will consider construction costs, O&MRRR costs, flood damage reduction benefits, and ecosystem restoration benefits to perform a second level screening of the plans.