Continuous monitoring of Eastern Lake Michigan bluffs using Sentinel -1 and Unmanned Aerial Vehicles (UAVs) data

In this study, we apply radar interferometric techniques to Sentinel-1 SAR data for continuous monitoring of unstable bluffs along the Lake Michigan coastline at Miami Park, South Haven, Michigan, where bluff failures have increased. This hazard risk has been an ongoing concern for County administrators and local property owners. The objectives of this study include two main tasks: (1) investigate the spatial and temporal displacement patterns in the study area; and (2) generate high-resolution 5 cm digital elevation models and orthophotos from temporal UAV surveys. The first task includes the extraction of the bluff deformation rates (velocities along the line-of-sight (LOS)) of the satellite, using a stack of Sentinel 1A radar imagery with ascending acquisition geometry acquired between 2017 and 2021, and applying the Small Baseline Subset [SBAS] InSAR time series analysis method. The second task includes the comparison of the temporal variations in mass wasting events to other relevant spatial datasets that can be potential triggering factors such as SBAS-based bluff deformation time-series, wave data, lake level variations, precipitation intensity, snow coverage, local lithology, and atmospheric temperature. Initial findings include: (1) areas witnessing high LOS deformation rates along the bluff were successfully identified from the SBAS analysis; (2) seasonal deformation patterns were observed in deformation rates and mass wasting (in the extracted time-series) along, but not away from, the bluff in areas witnessing high deformation rates and mass wasting; (3) seasonal deformation patterns were correlated with seasonal changes in freeze-thaw cycles and lake levels; and (4) the apparent acceleration of the observed LOS deformation and slope failure during the investigated period is likely caused by high lake levels and intensified onshore wave energy, increased precipitation and control of surface water, as well as the influence of the local glacial geology of the area (sand and clay mixture).