Investigating groundwater seepage control on bluff failure along Michigan coastline using UAVs

Using multi-temporal UAV-based optical and thermal observations, satellite imagery and lidar acquisitions, we investigated the role of groundwater seepage and glaciotectonic structures on bluff failure and retreat along the Michigan coastline. The adopted methodology involved three main steps. Firstly, identification of coastal areas showing evidence for bluff failure and/or retreat using satellite imagery, lidar derived DEMs and topographic analysis. Secondly, collection of field observations and multi-temporal (e.g., periods within the diurnal cycle, and after major rain events) UAV optical and thermal data over the identified areas and generation of 3D point clouds and orthomosaics from UAV imagery using structure-from-motion photogrammetry techniques over these areas. Thirdly, examination and correlation of field, UAV, and orthoimage datasets to map glaciotectonic structures (e.g., faults, folds, diamictite synclines produced by diapirs, and glacial dikes), stratigraphic units, and groundwater discharge/seepage locations. Results include the following findings. (1) glaciotectonic structures were successfully identified and mapped on the highly eroded bluff using RGB UAV images, (2) differences in heat capacity of sands and dimictite layers allowed characterization of structures and lithologies on the less eroded and slightly vegetated bluffs, and (3) localized ground water seepages occur at the base of diamictite synclines and creates identifiable bluff collapse patterns.