Total Rate of Longshore Sediment Transport in the Surf Zone: Field Measurements and Empirical Predictions

The total rate of longshore sediment transport was measured by streamer traps at 29 locations along the southeast coast of the United States and the Gulf Coast of Florida. The rate was also measured concurrently by traps and by short-term impoundment at Indian Rocks Beach, west-central Florida. Data on beach profiles, breaking wave conditions, and sediment properties were taken together with the transport rate. The measured total rates of longshore sediment transport were compared to predictions obtained with published empirical formulas, most of which have been calibrated mainly by sediment tracer measurements made on the (high-wave energy) Pacific coast. Transport rates measured in this study by the streamer sediment traps and the short-term impoundment along low-wave energy coasts were considerably lower than the rates predicted by empirical formulas. The empirical predictions appear to be unrealistically high for the low-wave energy settings investigated in this study. The linear relationship between wave energy flux factor and the total rate of longshore sediment transport contained in the commonly used CERC predictive formula is supported by the streamer trap measurements. However, a lower value of the empirical coefficient, 0.08 instead of the 0.78 recommended by the Shore Protection Manual, was determined by the trap data for low-energy coasts. The total rates of longshore sediment transport predicted by the Kamphuis (1991) formula which includes the influences of wave period, beach slope, and sediment grain size were about 3 times lower than the CERC predictions and closer to the measured values