Wave transformation on a transect crossing the surf zone of a fine grained, gently sloping barred beach has been further investigated with data from a 3-element coherent bottom-mounted pressure sensor line. In particular, field evidence is given for the formation of secondary waves when a moderate long narrowband swell propagated over two consecutive ridge and runnel system in both breaking and non-breaking conditions. Analysis are mainly done in the frequency domain, including also higher spectral analysis (bicoherence). The observed spatial variation in bicoherence values in the non breaking case is surprisingly low despite the fact that significant wave decoupling occurred after the bar. This implies that the phenomenon of decoupling can not be completely ascribed to the increase in water depth. On the other hand, wave breaking appears to weaken the strength of nonlinear coupling but does not affect (or at least hardly) the energy transfer to higher frequencies.
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