HARD STRUCTURE ORIENTATION AS AN INTRINSIC CONTROL ON ACCOMMODATION-SPACE DISTRIBUTION AND HEADLAND-BEACH FORM ALONG OHIO’S LAKE ERIE SHORE

Great Lakes beach evolution is governed largely by the interactions between fluctuating lake levels, which create and destroy sediment-accommodation space, and sediment supply, which is driven by bluff-shoreline erosion in absence of clastic riverine input. How these variables interact to drive shoreline change is well documented; however, the exact role hard structures play in changing the distribution of accommodation space requires more insight, particularly along the heavily modified southern Lake Erie shoreline. This paper investigates intrinsic controls on the distribution of sediment-accommodation space along harbor jetties and their influence on adjacent headland-beach geomorphology.

Historic aerial photographs dating back to the 1950s complement bathymetry datasets from the early 1900s, the 1940s, and the 1980s to provide information on the evolution of two harbor headlands along the southern coast of Lake Erie. Headlands Beach and Walnut Beach, Ohio, formed by littoral sand trapping along the up-drift side of structures emplaced for harbor-channel protection in the early 1900s. Shoreline advance was initially rapid at both sites as beaches began building against shore-perpendicular jetty sections. A change in jetty orientation to more shore-oblique is associated with a sudden reduction in beach-growth rates.

A threshold-driven reduction in beach-progradation rates is affiliated with shorelines reaching changes in breakwater orientation that greatly increased sediment-accommodation space at the shoreline . While changes in climate and lake level strongly control rates of sediment influx to harbor headlands along southern Lake Erie, beach dynamics are additionally influenced by shoreline accommodation-space distribution, which is heavily determined by hard structure design.