Barrier-spit geomorphology and inlet dynamics in absence of tides: evolution of the North Pond system, eastern Lake Ontario, New York State

Barrier systems have received much attention along microtidal oceanic coastlines, where countless studies discuss their evolution in response to Holocene sea-level rise, storm influence, and anthropogenic impacts. Lacustrine barrier evolution is not as well investigated and little is known about how lake-specific hydrodynamic processes shape barrier morphology. This study evaluates the evolution of a highly dynamic barrier section along eastern Lake Ontario in the context of varying water levels and winter-ice covers. Paleoshoreline reconstructions and volumetric analyses of nearshore sedimentation indicate the central portion of the studied North Pond barrier has been breached many times in different locations throughout the last century. Ground-penetrating radar (GPR) data corroborate mapped locations of former inlets, bound at the surface by recurved spit and dune ridges. Subsurface structural controls on inlet position are inferred from a spatial correlation with buried incised fluvial channels, formed during a Holocene lake-level lowstand. While subsurface controls caused two separate historical inlets to remain stationary while open, an episode of rapid inlet migration elsewhere along the barrier was facilitated by the prevailing direction of coastal currents and high lake levels, which favored overwash and rapid longshore sediment mobility across a low-gradient barrier section. Additionally, the sudden closing of an inlet after many decades of operation coincidental with the opening of another suggestively occurred alongside unusually high lake levels. These correlations suggest the degree of coastal inundation, predominantly a function of fluctuating lake levels and antecedent topography, represent strong controls on overall barrier geomorphology over decadal timescales.