FORMATION OF SAND SPITS DUE TO HIGH-ANGLE WAVE INSTABLITY IN A LAKE

Abstract

 In our previous study, we found that wind waves are obliquely incident at an angle greater than 45° to the shoreline of a sandbar located south of the mouth of the Nagase River in Lake Inawashiro. Along the shoreline of the northern shore of the lake, sand spits have been formed owing to high-angle wave instability. These sand spits still continue to develop. To investigate the deformation process, field observations were carried out on April 15 and July 30 in 2017, as well as the observation on September 2, 2019. Lakeshore changes were reproduced using the BG model (a model for predicting three-dimensional beach changes based on Bagnold’s concept). As a result, the moving velcity of the sand body predicted in this study coincided with 68 m/yr observed between 2020 and 2015 in the previous sutudy.