Abstract
Amounts of sediment yield, sediment deposits in dam reservoirs, and sediment digging in rivers and the sea were analyzed, as well as river channel change, relative sea level rise, and beach width change from around 1950 to 1990 in Japan, to quantitatively clarify the effect of sediment balance in catchments from mountains, rivers, to the sea. The approximate total amount of the sediment yield is 5,600 million m3, sediment deposits 800 million m3, and river digging 1,600 million m3 in the period, respectively, and more than half of the sediment yield is estimated to be potential sediment supply from rivers to the sea. On the other hand, the approximate total amount of sand loss in the sea is 2,000 million m3 and sea digging 700 million m3, respectively. All these data used in this study cannot fully explain the sediment balance in the catchments; however, they revealed that the river digging could be one of the major factors which affected the beach erosion in the period.
