The detection of the beach surface from the wave gage data is based on the assumption that the beach was exposed when no significant variation (less than 3 cm) was recorded for the duration of 10 s.
Figure 4 plots the wave gage data at three selected locations.
The time history of the front face of the bore is calculated from the wave gage data.
Unfortunately, the most shoreward wave gage was not located in the area of no topography change.
The present study aims 1) to present field data obtained through intensive and continuous measurements of both waves and swash-zone morphology by deploying many ultrasonic wave gages along the Hasaki observation pier and 2) to elucidate erosional processes occurring in the swash zone, focusing on the erosion of a berm under the action of storm waves based on the data.
In 1999 twelve air-borne type Ultra-Sonic Wave Gages (USWG) were deployed along the Hasaki pier as shown in Photo 2.
In July 2002 a new observation system was deployed by increasing the number of wave gages from twelve to twenty.
Because the wave gages did not record significant swash waves there, the increase in elevation was likely to be brought about by wind blown sand.
With the purpose of elucidating the cross-shore beach process, intensive and continuous field measurements were conducted for a few years by deploying many ultrasonic wave gages placed with a small spacing in the swash zone.