Changes in Shoreline and Wetland Shape Patterns Estimated from Satellite and Aerial Remote Sensing in Marshlands of Coastal Louisiana

Coastal Louisiana is currently experiencing rapid shoreline change along the margins of marshlands and bayous, due to the historical impacts of Mississippi River flood control, extracting fossil fuels, canal building, the Deepwater Horizon oil spill, and increasingly destructive hurricanes. To quantity recent shoreline change at increasingly high resolution, we have adapted a program first scripted in Google Earth Engine (GEE) by Mao et al. (2021, ISPRS Journal of Photogrammetry and Remote Sensing). This model was modified to use many thousands of 30-m transect lines generated from Landsat images to show the changes in the margins of marshlands of southeastern Louisiana over the past 10 years. Results showed that shoreline loss ranged in length from zero to over 450 meters per year from 2013-2023. The modified GEE program can be used in any other coastal area of the world for the same purpose. We further used QGIS and R Studio to carry out spatial analysis in a selected sub-basin of the western Barataria Basin heavily impacted by Hurricanes Zeta (2020) and Ida (2021). Aerial images (from NAIP) at 0.6 m pixel resolution from both 2019 and 2021 were segmented to compute polygon shape attributes, including compactness, elongation, eccentricity, circularity, convexity, and solidity of all marshland patches and the water bodies in the sub-basin. Our future studies have the potential to build from these existing GEE and QGIS codes to streamline the rapid analysis of seasonal change along the margins of marshlands and bayous.