Observation of infragravity wave processes near the coastal cliffs of Chabahar (Gulf of Oman)

Abstract

This study analyzed the characteristics of infragravity waves (hereafter IGWs) based on field observations collected near the plunging cliffs of Chabahar bay, Iran. Observations were made near Chabahar city during the summer monsoon season of 2018. The wave climate included two different durations of sea and swell predominance, with a maximum wave height reaching 2.5 m. Concurrent with the duration of the sea predominance, the ratio of IGW to swell wave height had an insensitive fluctuation against tidal variations, while this ratio had a strong negative correlation with tidal level during the high swell condition. The investigation of directional wave energy distribution revealed two correlated trends of shoreward and seaward IGWs with the wave regime.Larger values of the IGW reflection coefficients were observed during high sea wave conditions compared with high swell conditions. The IGW reflection coefficients decreased against swell energy growth with a logarithmic trend. The bound IGW energy fraction was studied using bispectral analysis. It is demonstrated that the maximum values of this parameter corresponded to high swell waves observed within low ebbs of the spring tide. The insignificant values of bound IGW energy fraction and the non-extended surf-zone revealed that most of the released IGWs originated from offshore and intermediate water depths. In addition, it was revealed that the inverse tidal trend of normalized IGW by swell height was due to bound IGW enhancement during ebb periods as a result of the nonlinear coupling of swell waves.