Detection and Analysis of Shoreline Changes Along Louisiana Barrier Islands: Grand Isle and Isle West Grand Terre

Louisiana barrier islands defend inland communities from storms, but they experience the highest rates of erosion in North America. Grand Isle and Isle West Grand Terre are barrier islands that have been subjected to stabilization and restoration. High resolution multispectral images and topographic LiDAR of Grand Isle and Isle West Grand Terre were gathered between 1998 and 2017. The images were processed to identify vegetation, bare earth, and water land classes using supervised classification techniques. Changes in land cover class were identified and quantified using postclassification image comparison tools. Digital elevation models were created from LiDAR point clouds and exported for shoreline extraction. Transects placed perpendicular to shorelines at 10 meter intervals measured shoreline position change. The study area experienced a 16.67% decline in vegetated land cover, a 47.57% gain in bare earth land cover, and a 0.39% gain in water class area between 1998 and 2017. The shoreline of Grand Isle experienced a landward movement of about 2.1 mm/yr and Isle West Grand Terre also saw landward shoreline movement at a rate of about 20.2 mm/yr. These rates are evidence of land area decline. This study identifies locations prone to change in Grand Isle and West Grand Terre. The results reveal changes that occur on Louisiana barrier islands with heavy human activity. Observations can be compared to long term or small-scale land cover change studies on the same coast.