## 3 Discussion of Results  
In order to analyze the influence of non-linear wave transformation on the cross-shore sediment transport, the sea bottom profile evolution graphs that were recorded from 14:00 on 27 September until the morning of 29 September 2007 were compared (Figure 2). Figure 2: _Cont._  
Comparing the profile on 27 September and the profile average over three measurements during the day of 28 September, it can be seen that the wave regime of 28 September led to the erosion of the underwater slope and formed a storm bar at distances of 50-70 m. The change in the wave regime from the evening of 28 September to the morning of 29 September led to the smoothing out of the erosion and accumulation of sand by the movement of the storm bar to the shore at the distances of 35-60 m.  
In the evening of 27 September, the sea swell was weak, the significant wave height at a distance of 220 m from the coast was 0.6 m, the peak period was 5 s. In the morning of 28 September, the wave regime altered, and until the evening the wave conditions were virtually stable: light swell with a peak period of about 7 s and significant wave height varying within the range of 1.1 m. Up until the morning of 29 September, the swell gradually attenuated, followed by a decrease in the period and height of the waves. The parameters of wave regimes--significant wave height (H\({}_{\text{s}}\)) and spectrum peak period (T\({}_{\text{p}}\)) at a distance of 220 m--recorded from the morning of 27 September to 29 September are presented in Figure 3.  
Figure 3: Wave parameters during the experiment period 27–29 September 2007. Figure 2: Sea bottom evolution from 14:00 on 27 September until 29 September 2007 (morning) (**a**) and corresponding daily averaged profiles (**b**). The waves propagated perpendicularly to the coast at all measurement points, and registration was carried out synchronously at 15 points along the coastal zone. According to visual observations, the breaking of all waves on 28 September occurred at a distance of 70-85 m from the coast, while the plunging breakers prevailed. As for the breaking of the highest waves, which was happening at a distance of 140-160 m from the coast, as the dominant wave breaking type was spilling, plunging breakers were significantly rarer. On 29 September, the waves broke only on the beach. The evolutions of the typical wave spectrum of 28 September, with the example of wave run 34, and the wave spectrum of the morning of 29 September (wave run 42) are shown in Figure 4a,b, respectively. The spectra were created by [PERSON]'s method with a Hamming window. Since the wave heights in different series of measurements differed as well, for the sake of a proper comparison, all spectra were pre-normalized to the corresponding wave dispersion. As can be seen from Figure 4, the wave spectra were narrow enough to separate the frequency ranges of the first and second harmonics. The frequency ranges of harmonics were determined by the minimum between the two peaks of the spectrum, corresponding to the frequencies of the maximum of first and second harmonics. For example, in Figure 4a, the frequency ranges of the first and second harmonics are 0.11-0.2 Hz and 0.22-0.35 Hz, respectively. The spatial evolution of the frequency range energy of the amplitudes of the first and second harmonics (hereafter referred to as simply the first and second harmonics) was presented as a percentage of change in the spectral energy of the corresponding frequency range, provided that the total energy of the spectrum over the frequency range of the first and second harmonics was 100%. The evolution of amplitudes 1 and 2 of the non-linear harmonics and biphases for the selected wave runs, 34-39, were measured during the day of 28 September, and wave run 42, which was measured in the morning of 29 September, are presented in Figures 5a,b and 6a,b, respectively. Let us consider the evolution of the spectra and amplitudes of non-linear harmonics and the phase shift between them more closely (Figures 4, 5a and 6a).