Shoreline Responses to Rapid Water Level Increases in Lake Michigan

TL;DR

This study uses satellite imagery to analyze shoreline erosion around Lake Michigan during rapid water level rises, highlighting the dominant role of wave and sediment transport factors over cross-shore processes.

Contribution

It provides high-resolution quantification of shoreline changes and identifies key wave-related and sediment transport factors influencing erosion during water level increases.

Findings

Shoreline recession ranged from 20 m to 62 m during 2013-2020.

Wave power and sediment transport divergence significantly correlated with erosion.

Cross-shore parameters showed weak correlation with shoreline changes.

Abstract

High-resolution multispectral satellite imagery was utilized to quantify shoreline recession at eleven beaches around Lake Michigan during a record-setting water level increase between 2013 and 2020. Shoreline changes during this period ranged from 20 m to 62 m, corresponding to 52-95% of the initial beach widths. Average estimated shoreline erosion across all beaches varied from 1% to 75% of the observed changes, with the remainder attributed to inundation. Significant correlations were found between shoreline erosion and wave-related factors, including offshore wave power, offshore bathymetric slope, storm energy, and potential alongshore sediment transport divergence. In contrast, parameters related to cross-shore transport, such as dimensionless fall velocity, exhibited weak correlations. Additionally, the results underscore the importance of distinguishing between immediately reversible changes (inundation) and morphological changes that could be reversible over longer timescales, when assessing the impact of rising water levels., The findings also suggest that in addition to waves playing a key role in regulating shoreline changes, alongshore sediment transport processes may play a more crucial role in beach erosion during significant water level increases than cross-shore processes, challenging traditional models of beach adjustment to rising waters.