STUDIES ON GEOMORPHIC POSITION AND TIMING OF REGOLITH SLIDE OCCURRENCE

在野外和实验室进行了水文地貌和土壤地貌观测，以获得雨致风化层滑坡的地貌位置和发生时间的知识。结果表明：1)土壤蠕变是日本东北部仙台周边丘陵上坡段风化层运动的主要过程；它的速度从每年0厘米到几厘米不等。在每年的雨季和在异常积雪的融雪期，在填满基岩空洞的土层/土层记录的速率相对较大。B或BC层位表现为块状运动，而A层位表现为流状运动。B层或BC层在倾斜基岩面上的轻微滑动似乎会引起上覆A层土壤颗粒的流动。(2)下坡段的风化层厚度通常小于1m，由上坡段通过上述过程提供，在大多数情况下，每处场地的体积小于1000 m^3，频率为几百年。在仙台附近的丘陵地区，引起地表滑坡的降雨总量在几百毫米到几十毫米之间，强度约为35毫米/小时，导致几个土层的管流迅速增加。3)最活跃的管流发生在B层或BC层。各土层的管道流量及其份额随降雨强度和持续时间的变化而变化。管流在多个层位/层位的变化响应取决于O和A层位的高渗流速率和B或BC层位的大储水量。(4)强降雨可引起上坡段（主要是顶壁）的风化层滑动，特别是在厚腐岩和高起伏的山丘上。这似乎是由于渗透水集中到管道上，管道的出口在上部，在弱雨的情况下是不活动的。少

Hydrogeomorphological and pedogeomorphological observations were carried out both in the fields and In the laboratory in order to obtain the knowledge on geomorphic position and timing of the occurrence of rain-induced regolith slides. The major results are as follows:1) Soil creep is the major process of regolith movement on the upper slope segments in the hills around Sendai, northeastern Japan. Its rate ranges from 0 to several centimeters per year. Relatively great rate is recorded at the soil horizons/layers which fill bedrock hollows in rainy season every year and snow-melt periods in the case of extraordinary snow accumulation. B or BC horizon shows block type movement while flow type movement prevails in A horizon. Minor slide of B or BC horizon on sloping bedrock surface seems to induce flow of soil particles in overlying A horizon.2) On the lower slope segments, the regolith, which is usually less than 1m thick and provided from the upper slope segments by the process as abov … More e, rapidly slides down with the volume of less than 1,000m^3 at a site in most case and the frequency of several hundred years. Rain which can induce regolith slides in the hills around Sendai is more than hundred and several tens of millimeters in total and about 35 mm/h in intensity, which leads to rapid increase of pipe flow st several soil horizons/layers3) Most active pipe flow occurs at B or BC horizon. Pipe flow discharge at respective soil horizons/layers and its share changes in response to intensity and duration of rainfall. The changing response of pipe flow at several horizons/layers depends on high percolation rate at O and A horizon and large storage capacity at B or BC horizon.4) More intense rainfall can induce regolith slides on the upper slope segments, mostly the headmost walls, also, particularly in the hills with thick saprolite and high relief. It seems to be due to concentration of percolated water to the pipes which have their outlets on the upper part and are inactive in the case of weak rain. Less