Exploration of Ishikawa Alluvium in Osaka Pref ewas carried out by means of electrical sounding. The thickness and the kinds of sedimentay materials of the Alluvium was thus determined. 1) the thickness is less than 8 metres 2) the materials are sand and/or gravel which, acting as permeable layers, often were concerned with water supplies in this region.
The southern plain of Saitama Prefecture is divided by Arakawa and Nakagawa lowlands into three eminences, Iruma, Kitaadachi and Noda, from west to east. Beside these two lowlands, Kawaguchi lowland extends south of Kitaadachi eminence. These eminences are consisted of diluvium in descending order as follows: Loam-mainly consists of volcanic ash, 4-5m in thickness Light colored bed-mainly consists of tuffaceous clay and sand, 10m in thickness First graval bed-mainly consists of gravel, often changing into sand, 5m in thickness Upper dark colored-bed mainly consists of clay, often int ercalating thin bedded sand, 20m in thickness Second gravel bed-mainly consists of gravel, often changing into sand, 10r in thicknes Lower dark colored bed-mainly consists of clay and sand, about 10-20m in thickness The lowlands are composed of allvuium in descending order as follows: Upper clay bed-mainly consists of silt and clay, often intercalating peat, 1-2m in thickness Upper sand bed-mainly consists of fine sand and clayey sand, 2-3m in thickness Lower clay bed-mainly consists of sand, rarely changing into gravel, about lm in thickness Of these strata, soft beds are Loam, Upper dark colored bed of diluvium, and alluvium of lowlands; hard beds are First, Second and Third gravel beds and Lower dark colored bed.
The topographic position of the landslide provinces, in which similar types of landslides are repeated periodica lly, are controlled by geology and geomorphological historyo f the area. Some landslide Provinces are situated along the axis of recent anticlinal movement or active faulting zone without geomorphological control. On the other cases, landslide provinces are distributed on sheared zones of basement complex. Causes of landslides of such types are mainiy steepness of valley walls, thick surficial materials on the estimated old river terrace, representing uprift ground movement of long time.