DEFORMATION OF HIROURA BEACH IN LAKE HINUMA DUE TO WIND WAVES AND GROUND SUBSIDENCE ASSOCIATED WITH 2011 GREAT EARTHQUAKE AND RECOVERY

Abstract

During the 2011 Great Earthquake, ground subsidence of 20 cm occurred in Lake Hinuma. Since then, lakeshore erosion became dominant on Hiroura Beach located in the eastern part of the lake, with pine trees grown along the shoreline being damaged and the root of the pine trees being exposed to waves. In this study, long-term lakeshore changes of the area were investigated using an old map produced in 1885 and aerial photographs taken since 1947 along with the site observation on February 24, 2012. Although Hiroura Beach was a cuspate foreland before land reclamation, the lakeshore has eroded by wind waves and a marked change was triggered by ground subsidence associated with the Great Earthquake. To recover sandy beach, the effect of beach nourishment was investigated using the contour-line-change model considering the changes in grain size of bed materials.