Calculation of wetlands erosion rates using Unmanned Aircraft Systems (UAS) and comparison with hindcast results from the hydrodynamic model
Calculation of wetlands erosion rates using Unmanned Aircraft Systems (UAS) and comparison with hindcast results from the hydrodynamic model
Abstract:
With the acceleration of sea-level rise, salt marsh resilience to continued environmental change has become a relevant concern. One critical erosive impact acting on salt marsh edge is dissipation from the wind-induced wave environment. During energetic conditions such as cold fronts passages, erosion rate could be accelerated by amplified wave energy.
Recently, marsh edge erosion has been determined through satellite imagery analysis. However, it is difficult to fully identify the causes of cold-front induced wetland erosion without analysis of short-term, high-resolution data.
A UAS system with a GPS base station and a rover GPS equipped UAV can provide 3D images of wetland boundaries for a given time. The GPS coordinates of the images are established by the rover GPS referenced to the base GPS and corrected by reference to Continuously Operating Reference Stations (CORS). The collected images are mosaicked by image processing tools, and the 3D map and digital elevation model are generated. By comparing the digital elevation model of the wetlands between two measurements, erosion rates can be established.
For the establishment of the relevant physical processes, a numerical model suite (Delft3D) is used to generate hindcast waves and currents at the sites in question during the measurement period; the result will be an evaluation of the wave and hydrodynamic energy at the sites in question. Empirical erosion rates established from previous laboratory experiments can be used to estimate erosion and establish erosion rates during the time of measurement. The Delft3D model can then be used to examine the physical processes active during the time of measurement.
Recently, marsh edge erosion has been determined through satellite imagery analysis. However, it is difficult to fully identify the causes of cold-front induced wetland erosion without analysis of short-term, high-resolution data.
A UAS system with a GPS base station and a rover GPS equipped UAV can provide 3D images of wetland boundaries for a given time. The GPS coordinates of the images are established by the rover GPS referenced to the base GPS and corrected by reference to Continuously Operating Reference Stations (CORS). The collected images are mosaicked by image processing tools, and the 3D map and digital elevation model are generated. By comparing the digital elevation model of the wetlands between two measurements, erosion rates can be established.
For the establishment of the relevant physical processes, a numerical model suite (Delft3D) is used to generate hindcast waves and currents at the sites in question during the measurement period; the result will be an evaluation of the wave and hydrodynamic energy at the sites in question. Empirical erosion rates established from previous laboratory experiments can be used to estimate erosion and establish erosion rates during the time of measurement. The Delft3D model can then be used to examine the physical processes active during the time of measurement.