GEOMORPHOLOGY OF A SANDY BARRIER COMPLEX ALONG EASTERN LAKE ONTARIO EVALUATED FROM GPR DATA AND AERIAL PHOTOGRAPHS: A STUDY OF LAKE-BARRIER INLET DYNAMICS

North Sandy Pond is a small freshwater estuary connecting to Lake Ontario’s eastern shore through a ~50 m-wide inlet. The sandy barrier between pond and lake is ~5 km long and ranges in width from 40 m to 360 m. The geomorphology of this barrier complex is investigated from newly collected GPR data, nautical charts, and historic aerial photographs in an attempt to understand how it is affected by high-energy storm events. This coastal environment is shown to be highly dynamic on a decadal timescale due to its abundance of sand and exposure to high wave and current activities that characterize Lake Ontario’s eastern shore.

Aerial images dating back to the 1950s and nautical charts dating back to the late 1800s document changes to this barrier, which include repeated inlet formation, migration, and closure. These events are corroborated in the subsurface by GPR data, where former inlet positions are resolved as channel-shaped bounding reflectors with irregular or chaotic internal reflection configuration patterns. These channel features are imaged to depths up to ~5 m below current lake level and show similar characteristics in size and shape to the currently active inlet. Lateral accretion surfaces resolved in GPR profiles reflect episodes of inlet migration. Surface features that are linked to these underlying structures include pond-ward recurved spits and inlet-channel remnants along the backbarrier.

While a total of 5 former inlet positions along the entire study site are interpreted from GPR data, only the two proximal to the modern, located ~600 m and ~1.2 km southward, respectively, are validated from historic aerial photographs. Given absence of pre-1950s images, older inlet positions are inferred solely from GPR data as the surface geomorphology has also been modified by non-inlet processes, including aeolian dune migration and human influences. Plans for future work are underway to help derive a better understanding of this lake-barrier system by improving the chronology of landform succession using ecologic datasets and evaluating barrier geomorphology with respect to historic storm records.