Geologic Controls on Rip Current Location and Formation

Rip currents are fast-flowing shore-perpendicular currents are capable of moving objects offshore very rapidly. Although they may vary in morphology, location, and dynamics, these currents present a significant hazard to beach-goers across the globe, including the northern coast of Prince Edward Island (PEI), Canada. Several of the rip currents along northern PEI appear to move very little from year to year and correspond to lakes, rivers, or swales behind the dune ridge. Given their quasi-persistent location and juxtaposition to back dune hydrology, it is hypothesized that nearshore bathymetry forming these rip currents are formed by buried river channels extending offshore in the subsurface geology. A series of ground-penetrating radar (GPR) transects and grids were collected along Brackley and Cavendish Beaches along northern PEI in July 2019 to examine whether such variations exist. Strong reflectors extending offshore are present in both alongshore transects and grids proximal to the rip currents and back dune swales, suggesting that the rip currents may be structurally controlled by the antecedent geology.