Climate-Induced Changes in Rates of Headland-Beach Progradation along the Southern Coast of Lake Erie

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Abstract

Isolated portions of the sediment-starved U.S. Lake Erie coast have prograded over the last 100 years in response to littoral drift disruption by hard-structure installation. Published nautical charts offer insight into decadal-scale sediment dynamics operating around this erosional coastline's prograding headland beaches. Nearshore-surface models constructed from historical bathymetry data sets show that headland-beach progradation occurs with little change in shoreface-profile shape; beach-area gain therefore provides a metric for sediment-volume change. A time-series analysis of beach growth, lake level, drought occurrence, and winter-ice cover suggests that headland geomorphology is partly climate driven. Decreased rates of beach progradation experienced along studied headlands between the late 1930s and early 1950s followed extreme drought conditions, exceptionally low lake levels, and low winter-ice covers. Reduced sediment supply to headland beaches is inferred by hampered bluff erosion during periods of low lake level, affiliated with less direct wave impact on bluffs, and drought conditions, associated with reduced groundwater-related mass wasting of bluffs. Similar drought and low-lake-level conditions existed throughout the 1960s; however, this period experienced high winter-ice covers and was unaffiliated with a change in headland-beach progradation rate, likely due to diminished sediment losses from adjacent nearshore regions during winter seasons. Reduced bluff erosion of the 1930s was induced by a combination of low lake levels and drought conditions and, along with nearshore-sediment losses in absence of winter-ice cover, stunted headland-beach growth during the subsequent period of lake-level rise. A decadal delay of headland-shoreline response to these climate extremes attests to the nearshore system's poor buffering capacity to environmental changes altering sediment availability.

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