Applications of unmanned aerial vehicles for mapping coastal processes and intertidal marine habitats

Abstract

To address increasingly complex research questions and global challenges (e.g. climate change and biodiversity loss), the development, refinement and need of new technology for monitoring marine coastal environments is increasing rapidly. Rapid advances in low-cost unmanned aerial vehicle (UAV) technology now allow for collection of centimetre resolution aerial imagery and topography suitable for assessing change in coastal ecosystems. We demonstrate the utility of UAV-based photogrammetry to quantify storm-driven sediment dynamics on sandy beaches and assess biotic communities on intertidal platforms by comparing on ground measurements to those that can be achieved with UAVs. Aerial imagery collected before and after major storm events is ideal for the assessment of coastal landscape change. High-resolution aerial imagery and digital surface models were acquired and change-detection techniques used to quantify change in the beachface following a high-magnitude event. An average beach erosion of 12.24 m3/m with a maximum of 28.05 m3/m was observed, and the volume of sand cut from the beachface and retreat of the foredune are clearly illustrated. Following the storm event, erosion was estimated at 7,256± 504 m3 along 550 m of beach. We also tested the utility of UAV remote sensing of intertidal reef platforms to traditional on-ground quadrat surveys for monitoring intertidal marine protected areas (MPA), and investigated the role of UAV derived geomorphological variables in explaining observed intertidal algal and invertebrate assemblages. Sub centimetre aerial imagery and digital surface models were acquired from intertidal reef platforms, and on-ground quadrat surveys collected intertidal biotic data for comparison. UAV's provided reliable estimates of dominant canopy-forming fucoid alga such as Hormosira banksii, however understorey species were often obscured and underestimated. UAV derived geomorphic variables showed elevation and distance to seaward platform edge explained 19.7% and 15.9% of the variation in algal and invertebrate assemblage observed. We demonstrate the benefits of low-cost UAVs through rapid data collection, full coverage census, and generation of UAV geomorphic derivatives for characterising intertidal biological variation and sediment dynamics in the coastal zone.