Field and aerial photograph surveys have been conducted at Tsuno-ore and Oritsu beaches facing the Kashima Sea, Japan, to investigate the morphological behavior of backshore dunes. Results of the field survey showed that the rate of change in backshore ground elevation increases with the area ratio of vegetation covering the ground. On the other hand, the aerial photographs over 10 years revealed that over time transverse winds divide artificial longshore dunes into smaller dunes, roughly 100m in length. Landward blown sand notably increased over gaps which appeared between the small dunes. At the Tsuno-ore beach, a small dune was deformed into a crescent barchanoid dune. The deformation of this dune was successfully simulated through an FDM computation. The Kawamura formula was employed in the 3D numerical model with additional terms representing the effects of sand surface slope and vegetation.