桃園草漯海岸沙丘的地形動力與演育及其應用

Seasonal topographic changes of the Caota sand dune were monitored at six survey areas from August 2019 to April 2021 by using RTK-GPS every four months. The topographic changes of the Caota sand dune are mainly controlled by winds and marine forces, where the north-east monsoon in winter becomes the strong onshore wind that blowing dry sand from the back beach to the landward and southward to form the foredune. Although short-term topographic changes varied among the survey areas, depending on the fronting beach width and dune vegetation cover, the erosional landform, such as the dune scarp at the base of the foreslope, was generally formed in summer. In autumn and winter, with the helps from forming dune ramp and slope slumping, the dune scarp disappeared and the foreslope recovered, while the foredune ridges slightly moved landward. Setting up grid of sand fences at the foreslope may intercept onshore sand transport and result in vertical sand accretion, but it is also to form a steeper foreslope that could be unstable and easily to trigger a large scale slumping. For a long run, this may result in increasing the dune vulnerability.