The Chenier Plain of southwestern coastal Louisiana is a Holocene strand plain composed of wooded beach ridges (cheniers) and intervening mudflat grassy wetlands. The mudflats form as prograding tidal flats along the open, but low-energy Gulf of Mexico coast; cheniers form from winnowing of sand and shells from the mudflats by waves during transgression. Mudflats are deposited when a Mississippi River delta lobe is nearby to the east, and cheniers are formed when distributaries switch to a more distant location farther east. All of the cheniers have formed within approximately the past 3000 yr or less and are progressively younger toward the present coastline. Spits are attached to the cheniers at estuaries; they grow westward in response to the dominant longshore currents. Currently, mudflats are prograding in Vermillion Parish to the east, while cheniers form in eastern Cameron Parish along with some regressive beach ridge development in western Cameron Parish.

This coast is microtidal with low wave energy. A high rate of subsidence as well as sea-level rise characterizes the Chenier Plain, which is subject to increased wave energy and mud transport every year during many cold-front passages and periodic storm surges associated with tropical cyclones of much lower frequency. Major storm surges can inundate the entire Chenier Plain, wreaking havoc on human settlements.