Cyclical changes in the coastal dunes of southern Louisiana

Historical and recent evidence indicates that the transgressive barrier beach headland of the Caminada-Moreau coast in Louisiana (Figure 1) is retreating rapidly (PENLAND and RITCHIE, 1979). Ground measurements in selective areas since 1979 have confirmed the average rate of erosion as being within the range of 10 to 15 meters per annum. In South Louisiana, sea level rise appears to be at a rate of approximately 1 cm per annum, with 90-95% of that rate being due to subsidence (SWANSON and THURLOW, 1973). In the absence of renewed primary sand supply from the Mississippi drainage system, shoreline change takes the form of erosional shoreface retreat which releases sand from the old deltaic and beach ridge sand bodies of the Lafourche delta plain. Some of this sand is transported alongshore where it is lost to tidal deltas associated with passes in the barrier islands, but most remains within the barrier system to nourish recurved spits, beach bars, and dunes at the distal ends of the barrier headland.