The Impact of Physical Processes along the Louisiana Coast.

The present-day coast of Louisiana is undergoing unprecedented change when compared with other coastal regions of the United States, Whereas most of its shoreline is retreating and its coastal hays expanding at the expense of wetlands, the Wax Lake and Atchafalaya deltas are prograding and forming new delta plains. Coastal processes responsible for reworking the lower delta plain and modifying the coast are modest, including very low-wave energy and a microtidal regime. However, occasional hurricanes and more frequent frontal systems produce elevated water levels and large waves (heights >1 to 2 metersl, which produce erosion, overwash, and barrier breaching. High subsidence rates coupled with eustatic sea-level rise and wave erosion are converting wetlands to open-water bays. Along barrier shorelines, this process is increasing tidal exchange, which is enlarging tidal inlets and the volume of sand captured in ebb-tidal deltas. Sequestration of sand in offshore ebb shoals depletes sand resources to the barrier chain. The segmentation, landward migration, and overall decrease in size of the barriers are a product of relative sea-level rise and the lack of contribution of new sediment to the system. Restoration of the barriers should be planned with an understanding that the Louisiana coast is evolving in a transgression. [ABSTRACT FROM AUTHOR]