Wave set-up, percolation and undertow in the surf zone
- 8 December 1983
- journal article
- Published by The Royal Society in Proceedings of the Royal Society of London. Series A - Mathematical and Physical Sciences
- Vol. 390 (1799), 283-291
- https://doi.org/10.1098/rspa.1983.0132
Abstract
Waves approaching a sloping beach induce a tilt in the mean water level within the surf zone. The existence of this `set-up' is here demonstrated by observing the mean flow in a straight tube laid parallel to the incoming waves; also by showing that the waves induce a siphon in a U-tube laid on the sloping bottom. It is argued theoretically, and confirmed by experiment, that the set-up should help to drive an offshore bottom current (the undertow) between the shoreline and the breaker line. Seawards from the breaker line the bottom current is reversed. The consequent convergence of the bottom currents may contribute to building up the `breaker bar'. Further experiments show that the mean onshore pressure gradient drives a circulation of water within a porous beach. The associated pattern of streamlines also extends into the land, inshore from the run-up line. Theoretically, the injection of dye at the sediment-water interface might be used to probe the porosity of the beach material.Keywords
This publication has 3 references indexed in Scilit:
- Mass transport in water wavesPhilosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, 1953
- THE ELECTRICAL AND MAGNETIC EFFECTS OF TIDAL STREAMSGeophysical Journal International, 1949
- SAND MOVEMENT BY WAVES : SOME SMALL-SCALE EXPERIMENTS WITH SAND OF VERY LOW DENSITY.Journal of the Institution of Civil Engineers, 1947