A study on the Shoreline Changes and Land Use along the Louisiana Coastal Zone

Purpose: Evaluate Louisiana’s shoreline changes using multi-temporal remote sensing datasets.

Supervisors: Dr. Yaw Twumasi (Southern University A&M College)

Software: ArcGIS Pro, ENVI 4.7, Digital Shoreline Analysis System (DSAS v5.1)plugin

Skills: Data processing, Data Analysis, Linear Regression Rate (LRR), Net Shoreline Movement (NSM), End Point Rate (EPR), Research

Introduction

  • This project endeavours to contribute valuable insights into the dynamics of coastal erosion along the coast of Cameron beaches, situated along the southeast coast of Louisiana using multi-temporal Landsat images and the Digital Shoreline Analysis System technique. Results obtained from this approach provide an immediate insight of coastal erosion evolution and help decision makers to address coastal issues more effectively within a relatively shorter time.

  • Landsat images of the study area were utilized to extract coastlines for different periods. The Landsat MSS and TM images were employed for 2001 and 2022. All images were projected in UTM Zone 15N for consistency. The Landsat 5 TM has 7 reflectance bands, and Landsat 8 and 9 OLI/TIRS have eleven bands with spatial resolutions of 30 meters respectively.

Coastal Extraction

The DSAS software utilizes a transect-based approach to detect changes in the coastline. DSAS version 5.1 was used to calculate the true statistics of the erosion and accretion in the study area. This involves generating perpendicular transects between a user-defined reference baseline and coastlines at multiple time points.

  • The Tasseled Cap technique was employed to transform the band channels into a new set of bands that enable clear interpretation for vegetation mapping. This transformation has previously demonstrated its effectiveness in shoreline extraction.

  • The Tasseled Cap technique incorporates composite bands including red, green, blue, NIR, short wave infrared-1 (SWIR-1), and short-wave infrared-2 (SWIR-2) to determine the brightness, greenness, and wetness levels of objects, with a specific focus on SWIR-2.

Results

Conclusion

After employing the DSAS tool, several outputs are obtained, including End Point Rate (EPR) and Linear Regression Rate (LRR). The end point rate (EPR) is calculated by dividing the distance of shoreline movement by the time elapsed between the oldest and the most recent shoreline.

Throughout 30 years, the study area fluctuated considerably with both erosion and accretion mechanisms. The most varied coastlines concentrate limitedly at 45 to 55 km, close to the river mouth. A maximum erosion rate of -42.4 m/year was observed. The spatio-temporal shoreline evolution results have shown that the eastern area of the study area was eroded with a high to very high speed, while the western area only recorded a very short period of erosion and then accretion.