USING REVOLUTIONARY CUBESAT IMAGERY TO PERFORM RAPID ASSESSMENTS OF SHORELINE CHANGE IN THE AFTERMATH OF MAJOR STORMS

Shoreline erosion resulting from rising sea levels and enhanced storm activity will have significant impacts on both human society and natural ecosystems. Understanding how coastal systems respond to episodes of significant storm events is important for future mitigation strategies. Multispectral satellite imagery has been used to map and track shoreline changes over time, although the moderate spatial resolution of these data products (i.e. 30 m/pixel for Landsat) and repeat interval (16 days) severely limit the accuracy of the interpreted shoreline position and ability to detect smaller scale changes that occur across a timeline of days (storm event). Most studies that have assessed morphologic changes to shorelines after energetic storms have relied on either labor intensive techniques (i.e. rod and level) or more recently, airborne photographic and LiDAR surveys. While the latter of these options do provide extensive spatial coverage and very-high resolution, the acquisition costs and/or limited access to the field site can be entirely prohibitive. The recent development of low cost, small satellites known as “CubeSats” represent the next step in assessing not only shoreline response to storms but all aspects of landscape change from space. The PlanetScope constellation of 150 CubeSats equipped with a four band multispectral sensor (RGB-NIR) acquires daily repeat global imagery at a resolution of 3 m. This high spatial resolution enabled mapping of the high water line (HWL), the most frequently used shoreline indicator, on imagery acquired a few days prior to and after Tropical Cyclone Oma severely impacted the southeast Queensland, Australia coast in February 2019. The shoreline position uncertainty of the PlanetScope-derived HWL shorelines is quantitatively assessed by comparing to a LiDAR-derived mean high water shoreline position and by calculating a proxy-offset bias. We show evidence of both significant progradation and erosion along the southeast Queensland study area in response to Tropical Cyclone Oma with some areas experiencing >40 m of change. This method represents a significant improvement over previous shoreline mapping techniques that would have been difficult to deploy within 3 days of the storm ending due to limited field access and demonstrates the potential of using PlanetScope to monitor global coastal systems.