Fusing UAS-SfM and airborne lidar to evaluate tropical storm impacts and respective recovery of a barrier island subaerial beach and foredune system

Abstract:

Coastal zones are highly dynamic environments that are constantly evolving from natural and anthropogenic-induced changes. The sustainability of these regions is largely dependent on their vulnerability to episodic storm events, which are predicted to fluctuate in frequency and intensity in the future. Efforts to quantify coastal response and respective recovery from hurricanes can improve resiliency modeling and conservation endeavors. In-situ methods of data acquisition are generally timely, costly, and restrict the spatial and temporal scope of studies. Alternatively, advances in geodetic imaging techniques have equipped researchers with the capability to obtain data with more flexibility and for larger scales. This presentation expands on previous work utilizing UAS-SfM and airborne lidar data to quantify the impacts of Hurricane Michael on Little St. George Island, Florida by quantifying the respective recovery of the island’s subaerial beach and foredune system.

We acquired airborne topobathymetric lidar data that was collected in November 2018 succeeding the landfall of Hurricane Michael on October 10, 2018. A follow-up survey was conducted in May 2019 utilizing a WingtraOne UAS platform to collect high-resolution images of the island. The images were post-processed using structure-from-motion photogrammetry to derive point clouds and elevation models of the beach and foredunes. For the recovery analyses, data products generally produced for storm impacts by the US Army Corps of Engineers were replicated. Volumetric change statistics were populated for 100 m bins to assess patterns of accretion and erosion. The uncertainty of these results was determined by using error propagation. The evolution of dune morphometrics including the dune crest and toe were determined for onshore transects every 10 m, and position of the shoreline was monitored. Results, in conjunction with previous work quantifying changes to the subaerial beach and foredunes from Hurricane Michael, indicate Little St. Georges’ response and respective recovery to this storm event. Preliminary results indicate the island is still experiencing a net loss of sediment, increasing its vulnerability to future episodic storms.