Abstract
A large amount of sand was deposited in the wave-shelter zone behind the offshore breakwater of Otsu fishing port in Ibaraki Prefecture, which was much smaller than the eroded volume of sand on the Kamioka-kami and Isohara coasts located south. Because the possibility of sand transport from the further south coasts was considered as the cause, the shoreline changes in the entire study area were analyzed using aerial photographs along with the analysis of the change in volume of sand on coasts. As a result, in a period between 1975 and 2009, the volume of sand has increased by 7.0×105m3 in an area of 4.5km length between Otsu fishing port and the Tenpisan Rock, whereas the volume of sand has decreased by 8.4×105m3 in an area of 13km length between the rock and Takado Point, indicating that the Tenpisan Rock is not a solid boundary for longshore sand transport.
