FIELD OBSERVATION OF THREE DIMENSIONAL CHANGES OF ARTIFICIAL BEACH AND APPLICATION OF EXPANDED HSU MODEL -THE EXAMPLE OF KEMIGAWA BEACH IN CHIBA PREFECTURE, JAPAN

摘要

Deformation mechanism of Kemigawa artificial beach in Tokyo Bay was investigated based on field surveys. In 1987 beach nourishment was conducted and the shoreline parallel to the seawall was created by the Chiba Prefectural Government. In order to enhance stability of nourished beach, curved groins were built at the south and north ends in 1991 after the nourishment, forming wave calm zones on their lee sides. Large-scale shoreline changes were triggered due to the construction. Beach changes were measured, and the changes of the beach profiles and the shoreline were studied. Comparison between the measured shoreline and that predicted by Hsu model was made. Furthermore, a three-dimensional predictive model of beach changes was newly developed and the comparison with observed beach changes was also made.