Measurement and Prediction of Long-Term Sediment Supply to Coastal Foredunes

Abstract

Sediment supply to coastal foredunes was measured over the period 1986-1992 at three sites along the accretional distal end of Long Point spit, Lake Erie. Sediment supply was determined from measurements of aggradation in the embryo and foredune made along transects perpendicular to the shoreline. Annual sediment deposition rates ranged from 2.6-10.3 m³ m^-1. Measured sediment deposition at two sites over the period May-December 1987 was 25% and 50% of sediment transport predicted using an equation developed by HSU (1974). Variations in sediment deposition from year to year, and between sites, were controlled primarily by variations in beach width, related to changes in lake levels and to local beach morphodynamics, rather than by variations in potential sediment transport based on wind velocity. It is argued that it is inappropriate to predict long-term sediment transport from instantaneous transport equations which make use of the wind shear velocity U_*. Furthermore, where beach width is typically less than 50 m, variations in beach width are a stronger control on rates of sediment supply to the foredune than the wind climate.