Seepage Flow in a Breaker Zone

Abstract

Seepage velocity in a breaker zone was measured with dye for visualization. Pressure sensors were also installed to obtain pore water pressure. Three cases of different incident wave periods were treated in laboratory experiments. The time-averaged pore water pressure was higher nearer to the shore, resulting in seepage flows, whose velocity was larger as the incident wave period was longer, generally running from onshore to offshore. The penetrated water flowed out from the permeable seabed at a bar top or on the rather offshore side of the bar top if a bar was remarkably developed. The pore water pressure in the breaker zone showed time variation depending on the wave phase including wave breaking and bore propagation. There was a phase where the pore water pressure decreased locally below the bar.