Infragravity Waves in Mobile-Bed Laboratory Experiments

Experiments were carried out in a flume 36 m long and 55 cm wide equipped with a piston wave generator. The sloping bottom consists of a loose material of low density (1.19 kg L^–1) with a median diameter d₅₀=0.6 mm in order that Shields and Rouse numbers are of the same magnitude as those of natural environments. Irregular waves are generated according to a JONSWAP spectrum. The waves are measured along the flume and bottom profiles are recorded in between repeated wave sequences. The infragravity modes amplitudes along the flumeare obtained for different wave climates. The correlation between the incident short wave envelope and the infragravity waves clearly indicates that the latter is the consequence of both a break point and a bound long wave release mechanisms.