MEASUREMENT AND PREDICTION OF LONG-TERM SEDIMENT SUPPLY TO COASTAL FOREDUNES

Sediment supply to coastal foredunes was measured over the period 1986 -1992 at three sites along the accretional distal end of Long Point sp it, Lake Erie. Sediment supply was determined from measurements of agg radation in the embryo and foredune made along transects perpendicular to the shoreline. Annual sediment deposition rates ranged from 2.6-10 .3 m(3) m(-1). Measured sediment deposition at two sites over the peri od May-December, 1987 was 25% and 50% of sediment transport predicted using an equation developed by HSU (1974). Variations in sediment depo sition from year to year, and between sites, were controlled primarily by variations in beach width, related to changes in lake levels and t o local beach morphodynamics, rather than by variations in potential s ediment transport based on wind velocity. It is argued that it is inap propriate to predict long-term sediment transport from instantaneous t ransport equations which make use of the wind shear velocity U. Furth ermore, where beach width is typically less than 50 m, variations in b each width are a stronger control on rates of sediment supply to the f oredune than the wind climate.