Infragravity waves recording in the area of Izmenchivoe Lake (South-Eastern Sakhalin)

Shevchenko G. V., Kirillov K. V.

The materials of wind-wave instrumental records obtained as a result of a field experiment in the area of the Izmenchivoe Lake spit (South-Eastern coast of Sakhalin Island) are analyzed. This experiment included setting up of three wind-wave and level gauges ARW-K10 in June—October 2007. During this period, several storms were recorded. One of them, occurred at September 25—26, related to extreme storms (the significant wave height exceeded 3.5 m, the maximum height reached 6 m). At different stages of its development, the ranges of periods were identified, at which the phase shift between the stations S3 and S8 located along the normal to the coast equaled zero, that corresponds to the edge-trapped waves propagating along the shore. These ranges (137—186 s and 68—82 s) corresponded to intervals with a linear phase change between stations S18 and S8 located parallel to the shoreline, which allowed us to estimate the velocity of long wave propagation equal to 1.8 and 1.1 m/s. The corresponding wavelengths were about 300 and 80 m, that is consistent with the typical quasirhythmic forms of the coastal relief in the studied area. The distance between the large forms (megafestones) was about 1.2 km, that is much larger than the typical lengths of the edge waves. During the storm peak, the average for the 4-hour interval amplitude of the edge waves in the indicated period ranges was 5.8 and 4.7 cm for the nearshore and 2.5 and 2.1 cm at the remote stations. The particle velocity estimates for station S3 were about 30 and 40 cm/s, respectively. High velocities of currents having opposite directions at distances of about 150 and 40 m are the cause of the formation of alternating zones of erosion and sediment accumulation.

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