Analysis of shoreline change for Dauphin Island, Alabama was conducted using the U.S. Geological Survey (USGS) Digital Shoreline Analysis System (DSAS) v.4.3 for ArcMap (Thieler and others, 2009) and vector shorelines derived from air photos and lidar elevation surveys. DSAS-generated transects were cast at 100-meter intervals along a user defined shore-parallel baseline. The intersections of transects with the mean high water (MHW) shoreline positions are identified by intercept points. The rate of shoreline change was determined by measuring the differences in the distance to each historical shoreline position from the baseline along each transect.

Three analyses of change rates were conducted using a combination of shorelines derived from different data sources. Shoreline change rates from the wet dry line (WDL) shoreline were derived from 10 sets of air photos from 1940 - 2015. Rates of change were also calculated using MHW shorelines extracted from 14 lidar datasets from 1998 - 2014. A final change analysis was conducted using a combination of all WDL (aerial) and MHW (lidar) shorelines, from 1940 - 2015.