Nearshore-zone quartz sands were examined to determine the effect of grain shape upon their transport and sorting. A grain-shape index was used to determine the mean Corey shape factor (SF) of each sample in a traverse that extended seaward from a Florida beach. The grand mean shape factor shows that the previously assumed value of 0.70 is slightly too high and that a better estimate is 0.65.
Calculation of two sediment-movement-threshold formulations indicates that the critical value had not been reached for the data set studied. Field observations indicate otherwise. It is suggested that for grains of lower-than-average shape factor (SF < 0.65), the movement threshold is considerably lower than that predicted by either formulation. This discrepancy could be the result of the subjective nature of the critical threshold value or a failure of the swing cradle and wave tank to duplicate fully the natural condition.