The purpose of this communication is to present the results of a serie
s of laboratory experiments aimed at better understanding the dynamics
of the motion of large bottom particles (cobbles) in a swash zone. In
this region, a thin sheet of water that results from the collapse of
a turbulent bore, runs up the beach and can induce the transport of re
latively large solid objects in the on-shore direction. The aims of th
e study were to: (i) mimic this process in laboratory experiments and
identify the associated physical processes involved and (ii) to develo
p a suitable theoretical model to describe the motion of cobbles. The
experiments employed a solid impermeable bottom and were conducted in
a long tank of rectangular cross-section. An impulsive hydraulic bore,
produced by a dam-break mechanism at one end of the tank, was used to
simulate the water motion in the swash zone. Solid objects of simple
discoid shape were used to model the cobbles. The results of the labor
atory observations were compared with model predictions. In the range
of external parameters used for the experiments (size and density of c
obbles, propagation velocity and height of the water front, slope and
friction at the bottom), a reasonable agreement between the measured a
nd calculated values of the cobble displacement as a function of time
was obtained. (C) 1998 Elsevier Science B.V.