SEDIMENT TRANSPORT & ACCRETION ABOUND THE COASTLINES OF JAPAN

Abstract

The process of sedimentation can be traced from its initiation as weathering of base rock, transport to the ocean by rivers, and its distribution by waves. The sediment supplied by a river is dependent upon catchment characteristics - topography, precipitation, vegetation and geology. The grading of this sediment can change over geologic time. The transport of material by waves is an important aspect of this overall movement, to a destination of either coastal plain or offshore shoal. The persistent occurrence and direction of ocean swell make this wave domain the most important in this process. In enclosed seas littoral drift is effected by storm type waves, per medium of a different beach profile from that on oceanic margins. Accepting that the wave climate has not changed significantly over geologic time, it is possible to picture the geomorphology of river and coastal plains to the present continental outline. The coastlines of Japan are examined in this paper with such an emphasis. Lowland so formed is of extreme economic importance. In order to promote accretion of further areas on a large scale, the character of the sediment and of the natural forces available at any location must be considered. Suitable structures and their siting within natural shoreline features are discussed.