Abstract
Mechanisum of generation of a large scour hole in the opening of artificial reefs and sand accretion of a port entrance due to alternations of the reefs at Uradome Beach in Tottori Prefecture were investigated by bathymetry survey results and a three-dimensional morphodynamc numerical model. The causes of the large score hole were due to alternations of the crown height and the width of the artificial reefs. In order to examine optimum measures against the scour hole and the accretion problems of the port entrance, the numerical analysis were conducted. From the numerical analysis, we found that the construction of a submerged breakwater in the opening of the reefs is one of the effective measures in order to prevent the large scour, however, the magunitude of lognshore currents behind the reefs become large and the sand accretion of the port entrance aggrevats. To prevent the accretion of the port entrance, nereshore currents should be controlled by submerged breakwaters near the port entrance.
