CHARACTERISTICS OF RECENT SANDY SHORELINE CHANGES IN THE KANSAI REGION IN TERMS OF COMPARISON OF TOPOGRAPHIC MAPS

Abstract

 Since the Meiji era, rapid modernization (urbanization) has led to substantial coastal erosion. Concretely, the averaged annual loss of beach area in Japan is reported to be as much as 160 hectares. Besides, the value of precious beach space has been recognized and coastal conservation measures have been implemented throughout the country. Since around 1990, there have been reports on topographic changes in a particular coastal area, but the changes in the location of the shoreline over an extensive area of analysis have not been understood. In this study, the characteristics of shoreline location change in the Kansai region were analyzed for each coastline type in terms of comparison of topographic maps. As a result, the sandy beaches where coastal conservation measures have been implemented are advancing (accretion), while the natural beaches without such measures are retreating (erosion). Furthermore, although the potential of fluvial sediment supply from the land area is increasing and improving, the erosion rate of sandy beaches is not affected by this evolution, suggesting the need for continuous coastal conservation measures.