Pan shot of swash rig
The region covered by wave uprush and backwash on a beach is the swash zone. Field measurements of swash processes are notoriously difficult while typical laboratory wave flumes are unsuitable for detailed measurements of swash processes because of the small swash produced and because of scale effects. These problems can be overcome by using an extremely large wave flume, but very few such facilities exist worldwide and their sheer size militates against their use for experimental work involving frequent changes of beach conditions.
Our Swash Rig generates full-scale swash in the laboratory without generating full-scale waves. The rig consists of a 20m long, 0.9m high, 0.45m wide, glass-sided flume with a water reservoir placed inside at one end. The reservoir is fronted by a gate designed to be raised at high speed. The sudden opening of the gate produces a large bore, which generates a large swash event on a beach, located downstream from the reservoir. Repeatability of the swash event is excellent.
Bores with speeds of order 3m/s are produced using a reservoir depth of 800mm and these have produced swash lengths of the order of 7m on a 1:10 impermeable, wooden beach and of the order of 4m on a 1:10 permeable beach consisting of very large shingle. These events are similar in magnitude to field-scale swash and are at least an order of magnitude greater than swash produced in typical laboratory wave flumes.