Understanding the processes of wetland boundary morphodynamics is critical to evaluating the vulnerability of wetlands. Specifically, analysis of changes in sediment supply at the wetland boundary due to the effects of global sea-level rise and local subsidence provides a more comprehensive depiction of future changes in coastal wetlands. This requires analysis through numerical modeling along the wetlands area to provide predictive information for future scenarios. However, sediment transport and morphological dynamics in adjacent bays have not been incorporated into regional models of wetland evolution. The study investigates the short-term sediment transport processes in a highly resolved wetland boundary within Galveston Bay during cold front passages. In-situ measurements verified the hydrodynamic and waves conditions at the salt marsh boundary during the period of two cold front passages. The model showed that the circulation of sediment fluxes to Galveston Bay was increased during the cold front passage. In addition, extensive wetlands flooding caused by cold fronts significantly affected the sediment supply to the wetlands. The sea-level rise adaptation of the salt marsh platform was verified by comparing the baseline and relative sea level rise models.

The lateral erosion of the salt marshes in Galveston Island wetlands was investigated through field UAV surveys. Using a GNSS receiver on the ground and a GNSS receiver attached to the UAV, highly accurate location information for the UAV images was derived through PPK analysis. Based on the collected UAV images with location information, Structure from Motion (SfM) by GNSS-supported aerial triangulation was conducted to generate orthomosaic images of wetlands. Drone surveys have been conducted seven times over a year, and the boundary erosion (represented by boundary retreat) for each period was calculated. The averaged error was less than 2 cm for the horizontal direction in the final orthomosaic images of wetlands. The average wave power, hypothesized to be a significant indicator of potential wetlands erosion, was calculated by investigating the wave climate of the survey area through a simplified numerical model. The relationship between wave power and erosion rate was then summarized. The average amount of erosion from 2019 DEC to 2020 MAR, where winds from north to south were dominant, was higher than from 2020 MAR to 2020 OCT. Much erosion was observed in a protruding part of the wetland. This is caused by waves coming from many different directions surrounding these parts. The erosion of this protrusion had a significant influence on the average erosion rate of the survey areas.