The Breton-Chandeleur Basin is a marsh and adjacent sound bordered on the southeast by remnants of the Chandeleur barrier island chain and on the west by the Mississippi River. Habitats in the basin range from freshwater forests to barrier island habitat. Marshes in the mid-part of the basin have been starved of sediment for almost a century and have some of the highest recent marsh loss rates along the coast. In contrast, some portions of marshes in the lower basin periodically receive fresh water and sediment from the river during high flows and have much lower rates of loss.

The priority projects selected for this basin reintroduce sediment and freshwater flows from the river to slow the rate of land loss, strengthen soils and build new land in the mid-basin (Mid-Breton Sediment Diversion) and in the lower basin (Lower Breton Sediment Diversion.) The ridge restoration projects (Bayou Terre aux Boeufs and Bayou la Loutre) will provide natural, structural protection by reducing wave and wind energy and buffering storm surge. Together, the diversions and ridges will prolong the life of the surrounding marshes while providing unique habitat for migratory birds.