Beach rebuilding period buffers Indiana beach erosion in Lake Michigan

Abstract

Recent high-water levels in the Laurentian Great Lakes caused widespread shoreline damage to beaches, homes, and coastal infrastructure. To quantify these shoreline changes and place them in historical context, shoreline imagery was analyzed to determine the magnitude, rates, and spatial variability of shoreline changes along the Indiana shoreline of Lake Michigan. The analysis shows that over the recent period of water level increase from 2013 to 2020, during which the water level rose nearly 2 m, the median shoreline recession along the Indiana coastline was 58 m and the median recession slope was 35:1 (shoreline recession : water level change). This magnitude of shoreline change is comparable to that experienced in other water level increase periods, 1965–1973 and 1990–1998. This recent shoreline recession was highly variable spatially, but not strongly correlated with shoreline type or position relative to littoral barriers. In spite of the widespread recent shoreline changes, the 2020 shoreline was generally more lakeward than previous high-water shorelines examined, with the exception of historical erosion zones downdrift of littoral barriers. Analysis of water level records and available wave hindcasts for the coastline suggest that while large, the erosion associated with the recent water level increase was tempered by a prolonged beach rebuilding period of low water levels and waves that resulted in an accreted shoreline that largely buffered the erosion associated with the water level increase. These results suggest that recent Indiana erosion could have been substantially worse had it not been preceded by the beach rebuilding period.