COMPREHENSIVE MEASUREMENTS OF LAKE MICHIGAN COASTAL CHANGE SPANNING THE LATE 2010’S HIGH STAND

Lake Michigan water levels rose 1.9 m from 2013 to 2020, exceeding monthly records and exacerbating coastal hazards including flooding, storm damage, and erosion. While sparse long-term measurements of planform coastal retreat are available for much of Lake Michigan, regional-scale measurements of coastal change within shorter timespans are needed to constrain temporal changes in erosion rates due to water level variability. These measurements have remained unavailable over large spatial scales due to a lack of suitable datasets, but recent topobathymetric JALBTCX LiDAR data acquisitions in 2012 and 2020 permit comprehensive measurements of coastal change. We used semi-automated methods to analyze LiDAR-derived DEMs from these two acquisitions for 800 km of the middle and southern Lake Michigan coast from Sturgeon Bay, WI to Muskegon, MI, delineating bluff and dune crest and toe positions, shoreline positions, and nearshore bar positions using profiles spaced every 5 m along the coast. We also measured erosion, deposition, and net volume change along this reach within 500-m long cells. Net volume change and planform retreat rates exhibited substantial spatial variability associated with changes in shoreline morphology and composition, barriers to littoral transport, and wave climate. Nearshore bars were absent from much of the WI coast, but multiple bars were prevalent along the MI coast. These measurements provide the most comprehensive evaluation of short-term erosion in Lake Michigan to date, helping to inform coastal resiliency planning efforts.