U.S. Geological Survey Digital Data Series DDS-79, Coastal Erosion and Wetland Change in Louisiana: Selected USGS Products

Introduction

The physical processes that cause barrier island erosion and wetland loss throughout the Louisiana delta plain are complex, varied, and not well understood over a range of temporal and spatial scales. Much of the debate in the science community is about the many natural and manmade processes that occur and their relative importance. There has been great discussion over the past 20 years about several proposed measures to reduce coastal land loss and restore the coastal ecosystem. The most recent of these plans are the Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA), Coast-2050, and now the Louisiana Coastal Area (LCA) Plan of Restoration. The value of various elements of the coastal system (vegetated wetlands, barrier islands, estuaries), the cost versus benefit of restoration, and the reliability of predicted results of a given management, restoration, or erosion mitigation technique have been the topics of much debate. With a better understanding of the processes that cause barrier island erosion and wetland loss, such predictions will become more accurate, and a clearer consensus of how to reduce and mitigate land loss is likely to appear.

The U.S. Geological Survey (USGS), as the Nation's primary science organization, has conducted research studies and monitoring in Louisiana for many years. Three of the major studies undertaken were the Louisiana Barrier Island Erosion Study, a cooperative effort with the Louisiana Geological Survey that spanned 1986 to 1990. A second study, the Louisiana Wetland Loss Study, was done cooperatively with the National Biological Survey (which became the USGS/ Lafayette Wetlands Research Center) and a team of scientists at Louisiana State University (LSU). The third and most recently completed study involved University of New Orleans (UNO) scientists and was on the geologic framework and processes of the Lake Pontchartrain basin. Smaller scale studies and data collection by the USGS and partners are continuing on mapping shoreline and wetland change and investigating subsidence processes responsible for the high rates of relative sea-level rise across the south Louisiana region, and on geologic surveys of offshore sand resources.

The USGS studies in Louisiana focus on developing a better scientific understanding of the processes that cause coastal erosion and wetlands loss, particularly the rapid deterioration of Louisiana's barrier islands, estuaries, and associated wetland environments. With a better understanding of these processes, the ability to predict erosion and wetlands loss should improve. More accurate predictions will, in turn, allow for improved management of coastal resources, such as setting new construction a safe distance from an eroding shoreline. Improved predictions will also allow for better assessments of the utility of different mitigation schemes. For instance, increased understanding of the processes that drive sediment and freshwater dispersal in the coastal zone will lead to more accurate assessments of the practicality and usefulness of large-scale freshwater sediment diversions from the Mississippi River. Understanding and quantifying the processes responsible for barrier island erosion will also aid in evaluating the relative merits of soft engineering techniques such as beach nourishment.