Wind-Blown Sand and Topographic Changes of the Coastal Dune at the Eroded Beach

The Nakatajima dune is approximately 1 km length and 0.6 km width, spreading from West to East which faces the Pacific Ocean. The dune has been changed in topography not only by wind-blown sand but also due to the limited sediment supply from the shoreline. The sand dune has transported to the East side of the dune by prevailing westerly strong wind which has produced parabolic dune. In contrary, the West side of the dune has been eroded, and decreased in the elevation of the sand dune due to no further sediment supply from the shoreline. Thus, this may facilitate the increasing of wave-overtopping during storm surges. Short-term and long-term topographic changes of Nakatajima dune have associated with beach erosion and coastal forest developments that is investigated based on aerial photographs, the data of wind, and regular field Survey. Topographical surveys are made using a Topcon GB-500 Global Positioning System (GPS) with Real Time Kinematics (RTK), which provides high-resolution control on topographical surveying with 1 cm and 2 cm of horizontal and vertical accuracy respectively. The surveys are being carried Out every two weeks in autumn to winter and once a month in spring to summer for two years (2007-2008). From the measured profiles,. the East edge of the dune develops 6-7 m/year with 7 m height. The averaged Volume of sand of the eastward migration was approximately 2450 m3/year into the Study area in the first year, which is well predicted by the formulae.