FIELD OBSERVATIONS OF INSTANTANEOUS CROSS-SHORE FREE SURFACE PROFILES AND FLOW DEPTHS IN THE SWASH ZONE

摘要

Observations of instantaneous and spatial mean water surface slopes and flow depths in the surf and swash zone are presented. With the assumption of hydrostatic pressure and small shear stress at the free surface, the surface slope is equivalent to the horizontal pressure gradient which is directly proportional to the total fluid acceleration. In the swash, the water surface slope is observed to be positive (dipping seaward/rising landward) and the total fluid acceleration to be negative for the majority of the uprush and the entire backwash, contrary to some recent suggestions. Intantaneous swash depth profiles show that the uprush lens is weakly convex in shape, consistent with previous work and friction effects at the run-up tip. In addition, a simple method is presented for obtaining rapid inter-swash bed level measurements and hence the crossshore variation in net total sediment flux for individual swash events.