Primary Factors of Beach Changes on South Kujukuri Beach: Ground Subsidence, Longshore Sand Transport and Crustal Movement during 2011 Great Earthquake

Abstract

The causes of beach changes on south Kujukuri Beach facing the Pacific Ocean were investigated on the basis of aerial photographs and the data set of the long-term measurements of the ground level by the Chiba Prefectural Government. On this coastal lowland, ground subsidence owing to the pumping-up of the water-soluble gas reached 90 cm between 1968 and 2012, resulting in the shoreline recession by 18 m given the foreshore slope of 1/20. Furthermore, ground subsidence of 9.3 cm occurred by the crustal movement during the 2011 Great Earthquake. These factors affected the beach changes.