Date of Award

2022

Publication Type

Thesis

Degree Name

M.Sc.

Department

Great Lakes Institute for Environmental Research

Keywords

Barrier beach, Breach, Coastal, Geomorphology, Hillman marsh, Pelee foreland

Supervisor

C.Houser

Supervisor

C.Proctor

Rights

info:eu-repo/semantics/openAccess

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Abstract

The Great Lakes are non-tidal, but experience significant water level fluctuations at hourly, seasonal, and decadal scales. In response to elevated water levels, barrier beach-ridges, including those located on the eastern shore of the Point Pelee foreland, experience accelerated erosion, overwash, and breaching leading to the removal or burial of vegetation, and damage to infrastructure and vulnerable habitat. Historical aerial imagery between 1931–2022 and annual average lake levels between 1920–2022 were examined to characterize barrier retreat and breach initiation, expansion, and closure. The timing and rate of transgression and progradation, overwash, and breaching are dependent on decadal-scale variations in water level. Ephemeral breaches and deposits were found to be a significant source of sediment transported landwards, this may represent a self-reinforcing cycle that promotes breach fill-in processes, even during high lake levels, and increases the barrier width and resiliency in response to further lake level fluctuations. This self-reinforcing cycle is disrupted by modified shorelines that limit sediment supply, leading to a persistent opening that can only close if water levels drop significantly, or new sediment is added to the system. Barrier breaching is a natural process in lacustrine systems with water level fluctuations, but the process is interrupted by shoreline modifications, putting critical ecosystems at risk.

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