Characteristics of waves in coastal waters of northeast Zhoushan Island during typhoons

To understand the characteristics of waves during the occurrence of typhoons, statistics and spectral variations of waves were investigated through a statistical analysis, and the reason for the variations was determined on the basis of wave data collected at two stations (in deep and shallow waters) in coastal waters of northeast Zhoushan Island during six typhoon occurrences:typhoons Chan-hom, Phanfone, Vongfong, Goni, Soudelor, and Dujuan. The results show that:① The maximum wave height recorded at the two stations during the Chan-hom are higher than that during the other five typhoons. ② The mean wave directions are mainly east and east-south-east in deep waters, and east, east-north-east and northeast in shallow waters during most of typhoons; underwater topography plays a major role in changing wave direction. ③ The paths of typhoons significantly affected the spectra obtained at the two stations; most wave spectra estimated during the Chan-hom, Phanfone, Vongfong, and Goni are double-peaked. During the Soudelor and Dujuan, more unimodal spectral waves were observed at the deep water station, while more multimodal spectral waves were observed at the shallow water station. The research results will be important as reference in the design of coastal structures as well as for disaster prevention and mitigation.