PHO Flood 01 AL.JPG

Waterbirds flock in flooded cornfields in the Atchafalya Basin, southeast of the Morganza Spillway, near Fordoche, La. on Tuesday, May 17, 2011, three days after the opening of the spillway to relieve flooding along the Mississippi River.

It appears likely that the Morganza Spillway will be opened next month, which could impact wildlife in some areas, according to the Louisiana Department of Wildlife and Fisheries.

Everything from bears to oysters could be affected by the release, which would send river water through a structure in Pointe Coupee Parish, then on through the Atchafalaya Basin toward Morgan City and finally into the Gulf of Mexico, relieving some of the strain on Mississippi River levees downstream.

The Mississippi River has been at or above flood stage for a record number of days in much of south Louisiana, and the Bonnet Carré spillway has been opened twice this year for the first time in history.


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An exact impact from opening the spillway isn't certain, but LDWF said in a release that there could be a detrimental effect on a wide range of animals and vegetation.

The following information is courtesy of LDWF:

Aquatic wildlife:

  • Salinites in Vermilion/Atchafalaya Basins
  • Public Oyster Seed Grounds in the Vermilion/Atchafalaya Basin
  • The oyster populations throughout the Terrebonne Basin
  • Crabs and shrimp typically migrate away from areas where salinity drops off
  • Displacement of finfish
  • Algae blooms and water levels returning to pre-flooding conditions may kill some fish
  • New invasive species may negatively impact native aquatic plant habitats and fisheries throughout the flood-prone areas
  • Colder water is likely to kill aquatic invasive vegetation.
  • Fish kills might be possible due to algae blooms and water levels returning to pre-flooding conditions.

Other wildlife:

  • Animals are at risk from avoiding rising waters, which could be a risk of drowning. Also, displaced animals may relocate to roads, where they are at risk of being hit by vehicles.