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The writer conducted an investigation of the relationship between the rainfall accompanying the Kanogawa typhoon and its resultant landslides, including landslides and the transportation of materials produced by landslides, and the scouring and deposition produced by the flood of Sept. 26, 1958 in the upper drainage basin of the Kano River (Fig. 1). Many investigations have been made of the various forms of damage caused by heavy rainfall, such as landslides, scouring, transportation and deposition produced by flood water, but little work has been done on the relationships between these phenomona from the upper to the lower course in a drainage basin. The main purpose of this paper, therefore, is to make clear these relationships. The conclusions of this paper are summarized as follows: 1) In the upper drainage basin of the Kano, many landslides have occurred as a result of heavy rainfall accompanying typhoon No. 5822. The severity of these landslides is especially high in an area from the southwestern to the northeastern part of the town of Yugashima (Fig. 2). These landslides have also coincided strongly with the area of heaviest rainfall even occurring in the area of the same rock type. From these observations, it might be said that there is little relationship between the distri-bution of landslides and of rock types, but that there is positive relationship between the distribution of landslides and of rainfall amount. The area where landslides are most frequent coincides with that the amout of rainfall is from 550 to 700mm. during this period of the typhoon (Fig. 2, Kawamura's Figs. 3 and 4). 2) Many boulder-size terrace gravels were also removed from riversides to stream beds by the scouring of flood water in the upper course from Yokose which is a town of Shuzenji (Fig. 1). Materials produced by landslides are mostly deposited on the mountain-sides and in small mountain stream beds except for landslides extending to the river beds. 3) It has been found by many researchers that the materials produced by landslides were transported only a very short distance, while the writer found that the bulk of the materials—derived from the great landslide in Ikadaba which is situated in the upper reach of the Omi River (Fig. 4, Tab. 3 and Photo 1) and composed of pumiceous sand and gravel was transported very long distance by the water of only one flood. 4) The locality of scouring and deposition by flood water could be determined by geomorphological characteristics such as the relationship between the ratio of river-width to valley-width and the stream gradient (Fig. 6, abscisa: the ratio of river-width to valley-width, ordinate: stream gradient). Geomor-phological factors determining the locality of scouring and deposition by flood water seem to be very important for flood control.

The River Watarase flows out from the western part of the Nikko Volcanoes, and runs southward through Ashio mountainland and empties into the River Tone in Kwanto Plain. Recently this river flooded frequently and the river floor of its lower course has been elevated. by deposits. The writers studied on the transporting materials of this river, specifically referenced to the upper course in Ashio mountainland from the geomorphological and potamological point, of view as a fundamental survey for civil engineering. In this paper, the transporting materials of Watarase River are stated briefly. 1. Suspended materials are supplied in large quantities from the settlingponds of Ashio Cupper Mine and its Refinery situated on the upper stream of this river. These materials are transported and deposited in the lower course and in the flood control lake, Akamanuma. 2. Solution is leached out in a great deal from Akagi volcano region because this volcano erupted in quaternary and its rocks are fish. Consequently the amount of solution of the tributaries from this region is far more than that of the tributaries from palaeozoic slate and granite regions in this mountainland. In Akagi region, as the volcanic ash and detritus are less cohesive and many landslips happen, so the.boulders and gravels of andesite are heaped on this river bed near Omama Town at the entrance to this mountainland. Therefore the fluvial gravel deposits of quartz porphyry and liparite from the headwater of the River Watarase are less than those of the anndesite. The elevation of river floor is mainly due to the detritus from Akagi Volcano. 3. The palaeozoic slate is apt to become small gavels, but granite is apt to become large boulders and not to become gravels. Granite. boulders are disintegrated abruptly into small pieces when they are transported in the river. 4. About 10meters gravel bed in thickness is seemed to be deposited in the flood plain without any depression in the river which has the same physiographical features as the River Watarase. On such thickness of river gravel bed, we consider it to be renewed by several floods, and accordingly the river terraces which have such gravel beds are not to be called alluvial terraces in such rivers. 5. The bed loads of this river are on the increase lately and about 500, 000 q. m. of sands and gravels are transported during a year.

The mountains of the upper drainage area of the Watarase have been wasted remarkably as a result of the destruction of the forest by smelter fumes of the Ashio Copper Mine, so that the bare land has become widely distributed there. This wasted land has greatly influeced flooding in the Watarase drainage area. Making clear the present conditions of the wasted land and the relationship between the supply of debris front bare land slopes and the sediments on the river bed from. the view point of the Watarase flood control is most urgent problem. There is considerable literature on the historical studies and on the. reclamation of the vegetal cover of, the wasted land but little work has been done in analysis of the present conditions of the, debris size distribution on the bare land slopes or the influences on the river bed deposits. The purpose of the present study is to determine how the debris size, distribution on the “tall” is controlled by th rock properties and what-relationship exists between the supply of debris from. the bare land slopes and the sediments in the river bed. Also this paper reports the results of measurement of the transported materials, and their solution, suspension, and saltation in the river. The general conclusion of this study are as follows: 1) The debris size distribution on the bare land slopes has been controlled. by the rock properties. For example, the debris of qurtzporphry has many boulders and gravels of 250 -64 mrn in diameter with few fine material (Fig. 5-1). The debris of liparite has few boulder and comparatively much gravel of 128mm diameter, size and, much fine material (Fig. 5, -2). The. frequency distribution of granitic debris shows many gravel particles of 32-8mm diameter, size and shows many gravel particles of 150mm in diameter with much fine mateial. That is. to say, the distribution has two peaks (Fig. 5-3). Finally, the debris, of Palaeozoic sandstone has many boulders and. that. of Palaeozoic shale has much fine material (Fig. 5-4). The facts above mentioned indicate the unit of debris size derived from the-different rock beds and determine the debris size distributions before the river-bed deposition. These determinations are important in the investigations of river bed sediments. 2) There are many “tali” below the bare land: slopes. Flood waters tra-nsport this talus rock debris to downstream locations where the consequent deposition increases lower course flooding. 3) Where the supply of debris. from the mountain side to the river bed is considerable, the mountain river bed shows sediments like mud flow deposits. 4) The particle sizes in the wasted land river bed portion are generally, smaller than those in river bed portion where the drainage area is vegetati-on-covered. 5) The amount of solution on the rivers of the wasted land is extremely small but the amount in suspension is very large.