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 (1190 kg m-3) with a median diameter d 50 =0.6 mm in order that Shields and Rouse numbers are of the same magnitude as those of natural environments. Time and length scales ratios are roughly 1/3 and 1/10. Irregular waves were generated according to a JONSWAP spectrum. The waves were measured along the flume and bottom profiles were recorded in between repeated wave sequences. A wave climate (characterized by its peak frequency and root mean square wave height) was run for several tens of hours, so as to reach bottom equilibrium conditions. H rms and infragravity mode amplitudes along the flume were obtained for transient and equilibrium bottom profiles. The long waves node positions and structure conform to model solutions of the linearized Saint-Venant equations. On the equilibrium bottom profile they are more energetic and the correlation between infragravity waves and the incident short wave envelope clearly indicate that they conform on both breaking point and bound long wave release mechanisms.