Multidecadal patterns of coastal profile change reveal low likelihood of beach recovery following a period of high Lake Michigan water level

Document Type

Article

Publication Date

1-1-2025

Abstract

Coastal erosion is a hazard for sandy beaches along the Great Lakes of North America, especially during periods of high lake level. A barrier to managing these hazards is the lack of a process-based understanding of nearshore sediment transport and geomorphic connectivity. In this study, a multidecadal dataset of beach and nearshore profiles collected at six sandy beaches along the eastern coast of Lake Michigan and contemporaneous hydrodynamic data are utilized to quantify long-term boundaries of sediment transport during accretionary and erosive conditions. Our results indicate that at most sites longshore sediment transport is the dominant force shaping multidecadal profile evolution. Accretionary wave conditions can generally only transport sediment onshore from shallow sediment ridges of the inner nearshore and from the lower reaches of the subaerial beach in longshore drift. In contrast, erosive wave conditions can mobilize sediment from all areas of the profile and transport it offshore. Sediments stored in deeper nearshore bars can be activated by high-energy erosive wave conditions, but these features likely primarily function as multidecadal sinks for eroded beach sediment given the dominance of offshore-directed transport for these wave conditions. Furthermore, these results suggest that the likelihood of recovery following high lake level should decrease in this region as extensive coastal armoring reduces sediment availability and increases reflective wave energy in the accretionary wave-accessible portions of the nearshore. Ultimately, this study puts forth a simple method for predicting the likelihood of future beach recovery that can be used to help guide coastal management.

Publication Title

Journal of Great Lakes Research

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