## 3 Results and Discussion
The next two areas defined for this level (L3) are illustrated in Figures 7 and 8 and they correspond to the computational domains Sph4--Southern RO1 and Sph5--Southern RO2, respectively. Thus, Figure 7 presents the model results for the time frame 7 October 2017 and Figure 8 those for the time frame 25 October 2017. The maximum values of the significant wave height and wave power are _Hsmax_ = 4.0 m and _Pwmax_ = 58 kW/m, for the case presented in Figure 7 and _Hsmax_ = 4.9 m and _Pwmax_ = 76 kW/m, for the case presented in Figure 8. In both cases the significant wave height and wave power have the maximum values in the same point, which is located in the northeastern side of the SWAN computational domain. Finally, Figure 9 presents the wave power scalar fields and energy transport vectors in the high resolution Cartesian domains (Cart1-Cart3). Thus, Figure 9a presents an average to high wave energy situation in the computational domain Cart1 corresponding to the time frame 8 November 2017. The maximum values of the significant wave height and wave power are _Hsmax_ = 4.3 m and _Pwmax_ = 54 kW/m. The points of maximum are located both in front of the Sulina bar, but that corresponding to the maximum wave power is closer to the nearshore. An important characteristic of the SWAN model simulations in this computational domain is related to the higher values of the Benjamin-Feir Index (_BFI_). _BFI_, or the steepness-over-randomness ratio, has been introduced formally by [PERSON] [43] and is defined as:  
\[BFI=\sqrt{2\pi}\;St\cdot Q_{p} \tag{8}\]  
where _St_ represents the integral wave steepness and is computed as the ration between the significant wave height and the wavelength and \(Q_{p}\) represents the peakedness of the wave spectrum and it is defined as:  
Figure 5: High wave conditions in the western Black Sea (computational domain Sph2), model results corresponding to the time frame 4 February 2017. (**a**) Significant wave height scalar fields and wave vectors (represented by black arrows); (**b**) wave power scalar fields and energy transport vectors (represented by red arrows). \[Q_{p}=2\frac{\iint\sigma E^{2}(\sigma,\theta)d\sigma\;d\theta}{\left(\iint\sigma E( \sigma,\theta)d\sigma\;d\theta\right)^{2}} \tag{9}\]  
This parameter is related to the occurrences of the high waves (the risks for the rogue waves apparition). Hence, _BFI_ is a spectral shape parameter that can be related to the kurtosis of the wave height distribution. In particular, for Gaussian-shaped spectra in the narrow band approximation [PERSON] (2016) showed that the kurtosis depends on the square of _BFI_. Furthermore, various experimental results show that for _BFI_ = 0.2 the maximum wave heights are very well-described by the Rayleigh distribution while for values of _BFI_ greater than 0.9 the ratio _Hmax/Hs_ is substantially underestimated. From this perspective, ([PERSON] _et al._, 2016) showed that the highest _BFI_ values occur in this area between the two points of maximum wave power and significant wave height, respectively, indicated in Figure 9a for significant wave heights of about 3 m and wave directions of 90 degrees (_BFI_ = 1.87). This indicates a very high probability of the rogue wave occurrence with very high wave energy. The importance of mentioning the rogue waves in this context is that besides the very high wave power, which they possess, they are also very dangerous for the human activities. These include the operational activities related to the maintenance of the devices, but also devices themselves might be put in danger by such very high and unexpected waves. Figure 9b illustrates a high wave energy situation in the computational domain Cart2 corresponding to the time frame 8 November 2017. The maximum values of the significant wave height and wave power are _Hsmax_ = 5.1 m and _Pwmax_ = 78 kW/m. The points of maximum are located both on the northern boundary, but in different places.