Spatial and Temporal Suitability of Monitoring Datasets for Assessing Coastal Change

The complex interactions between coastal processes and geomorphology occurs over a range of spatial and temporal scales. To effectively monitor and understand these interactions, coastal monitoring programs require appropriate data, technology, and analytical techniques covering those diverse spatiotemporal scales. This study aims to describe and compare coastal monitoring methods and technologies, by assessing their suitability across various spatial and temporal scales using three case studies from the Illawarra coastline, including Woonona-Bellambi Beach, Warilla Beach, and Minnamurra Beach. These sites were selected based on the sediment compartment they form part of, anthropogenic modification, data availability, and technology for geospatial analyses.

The study utilises satellite records from 1987 through derived data products to assess shoreline stability at each study site, with notable changes associated with anthropogenic structures or activities (e.g., seawalls, dune management or installation of river training walls) and river inlets. High temporal coverage photogrammetry combined with high spatial resolution airborne LiDAR data was used to assess foredune geomorphic change over seven decades to identify the relative stability at each site. Results show erosion and recovery at Woonona-Bellambi and Warilla Beaches following large-scale storm events, as well as foredune volume changes due to anthropogenic modifications. Minnamurra Beach experienced minimal impact from both human activities and storm events. Unmanned Aerial Vehicle (UAV) LiDAR surveys provided exceptionally high spatial resolution data; however, data processing workflows require improvement. Terrestrial Laser Scanning surveys were time-intensive but delivered very high spatial resolution, with data coverage for the beach face and foredune front.

The results emphasise that different datasets and trend indicators offer complementary insights into coastal change. Long-term trend analysis benefits from high temporal coverage and resolution, such as satellite-derived shorelines, while event and sub-annual change assessments require high spatial resolution with targeted coverage. A framework has been developed to support selecting and applying suitable monitoring technologies and datasets most effective at capturing the spatial and temporal range of processes and trend indicators of interest.

Overall, this research project focused on closed compartment beaches of the Illawarra Coast that have been exposed to erosion and are slowly recovering. Application of this study to other compartments in NSW that exhibit different morphodynamics will allow the framework to be refined, become more applicable to the coast of NSW, and improve the use of coastal monitoring data to guide decision making and coastal adaptation.