Along the eastern coast of Lake Michigan, bluff failures are influenced by lake water levels, bluff groundwater saturation, and lithology. The bluffs are composed of unconsolidated glacial tills interbedded with/overlain by glaciodeltaic sand and lacustrine silt and clay, and experience toe erosion, creeping, and slumping. Lake Michigan water levels peaked at record levels in 2019-2021 following a prolonged below-average period ( -2013), accelerating toe erosion and prompting widespread public concern. This study examines three sites in Michigan: Lakeshore Dr. in St. Joseph (SJo), subdivisions at Miami Park (MP), and a natural area near Ludington (LU), all exhibiting active groundwater seepage at clay layer contacts in the bluffs. Surface point clouds derived from UAS (drone) nadir and oblique imagery (2016-2022) and 2012 LiDAR datasets document erosion, landslides, and bluff top retreat at all sites. The unmanaged LU site experienced 177,000 ± 2,300 m³ of erosion at high water levels from 2019-2021, roughly three times the 2012-2019 rate. At MP, an area with several distinct management strategies applied, significant retreat occurred adjacent to locations armored with large boulders, with slumps causing losses of as much as 5-10m, where nearby densely vegetated slopes with active surface water management near the bluff showed minimal erosion. These observations highlight the complex interaction of management decisions and natural drivers to shape bluff failure outcomes.
