Lower Mississippi RIVERKEEPER

Report addresses flood concerns, recommends dredging of Alligator Bayou and the restoring of a more natural hydrologic pattern

Download the full report here: Review_of_Proposed_Water_Manage.pdf

"In April, 2009, the Alligator Bayou floodgate was opened at the direction of Iberville Parish to drain water that had been held on privately owned land because the landowners were threatening a lawsuit against the Parish. Upon opening of the floodgate, water levels within the Spanish Lake sub-basin decreased dramatically. Draining of the water held for nearly 60 years in the sub-basin has caused an increase of invasive species, created problems for local wildlife, and reduced navigation within canals and other waterways; however, it also has allowed germination of desirable tree species which have experienced little or no regeneration since water was impounded." (page 24)

Aerial view of Spanish Lake, March 2002.

"First and foremost, leaving the floodgate open has caused the bayous and canals to become choked with invasive herbaceous species, increasing friction and decreasing water conveyance, thereby increasing flood risks. Secondly, leaving the floodgate open has caused the bayous and canals to become essentially non-navigable." (page 48)

Aerial View of Spanish lake, October 2010.

LEAN and LMRK support the responsible implementation of a water management plan for the Spanish Lake Basin based on sound scientific information. The above quotes are from a report we have recently received that was prepared for Shaw Environmental and Infrastructure Group by Dr. John Day, Dr. Gary Shaffer, and Dr. Rachael Hunter in September, 2009. The report compiles an extensive amount of historical and hydrologic data pertaining to the Spanish Lake sub-basin. The water management plan within the report states that "prior to implementing the proposed new water management plan, the existing floodgates at Alligator Bayou and Frog Bayou will be replaced with higher capacity structures..." and "Alligator bayou will be dredged from the structure to where the dredged canal intersects with Alligator Bayou, a distance of about 1.4 miles."(page 44) The report outlines a flood gate operation plan designed to create a more natural hydrologic pattern for the basin while maximizing flood storage capacity and promoting the restoration Cypress/Tupelo swamp habitat. "Maintaining several feet of water in the canals and bayous of the Spanish Lake sub-basin, preferentially through dredging or secondarily through managing water levels with the floodgate, will have multiple ecosystem and human benefits, including:

• Typical rainfall patterns would raise water levels to be high enough to enter the swamp ecosystem many times during the growing season, and several times enough water would be captured to flood the bottomland hardwood forests. This pulsing paradigm offers optimal hydrologic conditions for wetland forest growth and regeneration.
• Maintaining water levels around 3 feet would kill nuisance vegetation, such as giant cutgrass, and prevent the choking of canals bayous. This would increase flood protection by removing friction from these important drainage arteries.
• If minimum water depth is maintained within drainage channels recreational fishermen, hunters, birders, boaters and general ecotourists could navigate the ecosystem without damaging or stranding their vessels."(pages 49, 50)

"From our collective wetland experience, the proposed management plan offers a scientifically sound foundation on which to manage water levels within the two sub-basins. The proposed plan accommodates competing interests within the Spanish Lake sub-basin." (page 7)

Download the full report here:Review_of_Proposed_Water_Manage.pdf

John W. Day, Jr., Gary P. Shaffer and Rachael G. Hunter. "Review of Proposed Water Management Plan for New Alligator Bayou and Frog Bayou Water Control Structures and Related Environmental Impacts - Bayou Manchac, Louisiana" Prepared for Shaw, Environmental and Infrastructure Group, September 18, 2009.