Land Type and Shoreline Change on Louisiana Barrier Islands Grand Isle and West Grand Terre: 1998-2017

Authors: Lindsey Aucoin*, Sam Houton State University
Topics: Geographic Information Science and Systems, Geomorphology
Keywords: GIS, Grand Isle, Louisiana, Barrier Islands, LIDAR
Session Type: Poster
Day: 4/12/2018
Start / End Time: 1:20 PM / 3:00 PM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded

Located approximately 100 miles south of New Orleans, Grand Isle and West Grand Terre are home to a historical Fort Livingston and more than 1,400 residents. Land loss of about 24 square miles per year along Louisiana’s coastline prompted remote sensing surveys of barrier islands between 1998 and 2017 that provide high resolution elevation and image data, which can be compared for changes in shoreline and land type. This study conducts a large-scale investigation of the changes in Grand Isle and West Grand Terre land/water boundary and land area over ~20 years. Lidar point cloud data is interpolated to create bare earth surface digital elevation models and elevation contours for each island. The contours representing shoreline elevations are used in linear referencing to measure change in shoreline position and change rates. High resolution, orthorectified aerial images are corrected for radiometric stretch, mosaicked, projected, and identified as bare earth, vegetation, or water class types. These classified images were entered into the ERDAS Imagine change matrix tool to calculate the area of land that experienced change. Grand Isle, the largest of the two islands, experienced shoreline movement of approximately 20 meters oceanward between 1998 and 2013 and W Grand Terre experienced landward shoreline movement of approximately 97 meters. Combined area change over the two islands shows a large increase in West Grand Terre backbarrier after 1998, but an estimated loss of 20,000 meters per year after 2012. Effects of coastal engineering efforts are evident within this 20 year period.

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