Aerial imagery collected before and after major storms is ideal for the assessment of coastal landscape change driven by individual high-magnitude events. Using traditional satellite sensors and manned aerial systems, however, can be challenging due to issues related to cloud cover, mobilization expenses and resolution. Rapid advances in unmanned aerial vehicle (UAV) technology now allows for cost-effective collection of aerial imagery and topography at centimetre resolution suitable for assessing change in coastal ecosystems. In this project we aimed to demonstrate the utility of UAV-based photogrammetry to quantify storm-driven sediment dynamics on sandy beaches on the open-coast shoreline of Victoria, Australia.
UAV-based aerial photography was collected before and after a major storm event. High-resolution aerial imagery and digital surface models (<10cm) were acquired and change-detection techniques were applied to quantify changes in beach slope, elevation and vegetation communities. By combining the aerial imagery and derived topographic datasets, we demonstrate the advantage of UAV-based photography for rapid high resolution data collection in semi-remote locations, its utility in setting unlimited virtual vantage-points and discuss the valuable perspective it provides for tracking landscape change.
Beaches are dynamic in nature driven by coastal processes (ocean waves, currents, tides) geological (grain size) and climatic conditions (rainfall). Future climate change predictions such as a rise in mean sea level and shifts in wave climate make beaches particularly vulnerable to increasing risks from beach erosion and inundation and a diminishing of the protecting function they provide. This is further exacerbated by coastal planning where often difficult decisions need to be made to mitigate the impacts of a retreating shoreline. Often in affluent societies, hard engineering solutions are commonly applied requiring ongoing maintenance to protect high value beachfront properties.
Remote sensing tools (such as satellite and aircraft imaging) may provide full coverage data to characterise changes in beach morphology but are limited in terms of the spatial and temporal resolutions and relatively high costs of acquisition. Satellite imagery acquisition can also be challenging due to orbital cycles determining the timing and repeat of image capture and challenges associated with cloud cover obscuring scenes. Aircraft provide alternatives for sensor platforms and are capable of more scale appropriate data for coastal geomorphic studies including the capacity to collect three dimensional point clouds such as from light detection and ranging (LiDAR). This has advantages in terms of the ability to perform surveys on demand at a higher resolution afforded by satellite sensors but the reality is this is often time series data are not acquired due to prohibitive costs associated with temporal capture.
More information on this project can be found on the Pix4D website, and the full research paper can be accessed here.