Influence of lake levels and ice cover on a modified shoreline Ohio's headland beaches

Abstract

Ohio's Lake Erie shoreline, situated along the high-energy south-central Lake Erie coast, is characterized as a sediment-starved, wave-dominated erosional coastal system. Harbor-protecting structures installed in the early 1900s have fragmented the littoral system, which trends from W to E across the area, trapping bluff-derived sediments on their up-drift sides. The studied depositional harbor headlands of Lake County (i.e. Headlands Beach) and Ashtabula County (i.e. Walnut Beach and Conneaut Beach) are located along a ~65 km stretch of the south-central Lake Erie shoreline. Given many shared similarities and similar degrees of exposure to lake-level variations, winter-ice covers, and storm conditions (with associated surge levels, waves, and strong coastal currents), the geologic and anthropogenic distinctions between the sites need to be evaluated as potential drivers of coastal change. Historic shoreline positions, mapped from georeferenced aerial photographs, provide a chronology to evaluate the recent geomorphic evolution of these headlands with respect to these physical forcing parameters. Ground-penetrating radar (GPR) data reveal changes in prograding clinoform (i.e. preserved foreshore deposits) geometry, attesting to the inherent dynamics of headland beaches, which have been impacted by episodic erosion and deposition at decadal timescales. Multiple regression analysis of net beach growth, derived from shoreline positions, versus lake level and ice cover suggest that high lake levels are more strongly associated with beach growth overall; this is surprising given variable sediment sources and beach compositions from site to site. Beach growth during elevated lake levels are likely attributed to increased sediment fluxes from sourcing bluffs. Ice cover appears to play a secondary, yet important role in headland evolution as both an erosional and depositional mechanism capable of entraining course-grained sediments and reshaping shorelines. The design of harbor structures influences sedimentation at the