Analysis of the system on sedimentation of clastic materials from valley head to littoral zone

本研究的目的是了解从阿部川的谷口到美保海岸的砂、砾石等粗粒物质的沉积系统。1、静冈县的阿部川在谷口发生了大规模的滑坡，这是1707年地震造成的。阿部川是辫状河系，碎屑物质较多。2、通过地理研究所出版的地图，研究了阿部川的三角洲形态和美保海岸的海岸形态。到1975年，阿部河三角洲的海岸线像一条凸曲线一样活跃。但1985 ~ 2000年三角洲海岸线没有出现凸曲线，三角洲处于活动状态。因为阿部川河床上的沙子和砾石被移走用作建筑材料。现今三角洲活动轻微，海岸线不规则。3、现今美保海岸具有侵蚀条件。到达阿部川三角洲的粗物质被沿岸流沿着沿着美保海岸向北输送。阿部川河床上的粗料短缺，也沿沿着美保海岸运输。粗物质的缺乏导致了三保海岸的侵蚀状况。

The object of my research is to know the system of sedimentation of coarse materials like sands and gravels from the valley head of the Abe River to Miho coast.1, The Abe River in Shizuoka Prefecture has big landslides at its valley head, which have been caused by the 1707 earthquake. The Abe River with the braided river system is characterized by much more clastic materials.2, I have studied the delta forms of the Abe River and coastal forms of Miho coast through maps published by Geographical Institute. The delta of the Abe River was active with the coastal line like a convex curve by 1975. But the coastal line of the delta from 1985 to 2000 did not show a convex curve, and the delta was inactive. Because sands and gravels on river beds of the Abe River were removed for constructive materials. The present delta becomes slightly active with an irregular coastal line.3, The present Miho coast has erosive conditions. Coarse materials reached the delta of the Abe River are transported by coastal currents to north along the Miho coast. A shortage of coarse materials on river beds of the Abe River was also transported along the Miho coast. The shortage of coarse materials causes erosive conditions of Miho coast.