Ecological Systems and Devices Annotation << Back Features of Swell and Infragravity Waves Manifestation in the Coastal Zone of Sakhalin and Kuril Islands Kovalev D.P., Kovalev P.D., Borisov A.S. Wave fi eld in swell and infragravity (IG) wave period range is investigated. To perform the study a long-term dataset of sea level fl uctuations obtained at ten points in the coastal zone of Sakhalin Island and Kuril Islands is used. The dataset collected by bottom-mounted pressure transducers and sampled every second. Examination of spectral curves of sea level fl uctuations in the range of swell and IG waves shows their different behavior in different observation points. Two types of wave energy spectra are distinguished. One has several signifi cant peaks in swell and IG wave ranges (for Kurilsk, Yuzhno-Kurilsk and Kholmsk) and another one contains the energy rise in a wide range of swell waves and has its main maximum at periods from 7 to 11.8 s without any signifi cant peaks (for the remaining seven observation points). The analysis of the fi rst spectra type shows that peaks in wave spectra are the harmonics of main periods and formed as a result of transformation of waves in shallow water due to the local nonlinearity effects. The analysis of waves in Kurilsk shows the presence of fi ve peaks at periods from 4.3 to 10.4 s in the spectra of wind waves and swells. Their interaction can lead to the formation of harmonics, with the periods which are close to the period of peaks we observe in the spectra of IG waves. The analysis also shows that the generation of IG waves is mainly determined by swell waves. High total wave energy in the wind and partly in the swell wave ranges contributes to the reduction of mode structure and stochastization of the IG wave spectrum, which causes the absence of a distinct mode structure. The wave structure analyzed using the dispersion relation obtained by Ursell. It is shown that near Kurilsk, the IG wave energy can also be trapped and propagate along the coastline as edge waves at periods of 25.2 – 272.3 s. Since a part of IG wave energy can be refl ected to the sea, the coastal transverse profi le of the refl ected normally incident on the shore IG waves is calculated for a simple inclined bottom profi le approximated by a model with a linear slope. It is shown that the transverse profi le of the refl ected waves signifi cantly depends on their period. Such refl ected waves can form linear bars. Keywords: wind waves and swell, edge waves, infragravity waves. DOI: 10.25791/esip.10.2024.1475 Pp. 03-14.