Barrier beaches and breaches: Historical changes on the Point Pelee foreland

Abstract

The Great Lakes are non-tidal, but experience significant water level fluctuations at hourly, seasonal, and decadal scales. A rise of 0.83 m was observed between 2013 and 2020 on Lake Erie with the annual water level near the previous record high of 174.89 m set in 1986. In response to elevated water levels, barrier beach-ridges located on the eastern shore of the Point Pelee foreland, in the Lake Erie’s central basin, experienced accelerated erosion including overwash and breaching, removal or burial of vegetation, and damage to infrastructure and sensitive habitat. Historical aerial imagery between 1931 and 2020 and annual average lake levels between 1920 and 2020 were examined to characterize barrier retreat and breach initiation, expansion, and closure. Results indicate that the barriers have transgressed at a rate of >1 m y−1, but the rate of transgression and progradation, overwash, and breaching are dependent on decadal-scale variations in water level. Ephemeral breaches and delta deposits were found to be a significant source of landward sediment transport if breaches remained open for multiple years. 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. While common patterns of barrier dynamics were found throughout the time series, human impacts may modify historic barrier transgression rates and breach and recovery processes.