It is important to understand the mecanism of sediment transport in steep slope channels when we consider countermeasures for disasters due to sediment movement in mountain rivers and fans. The author have studied on sediment transport in steep slope channels whose slopes are larger than 1/100. In this report first the classification of sediment transport phenomana is discussed, second the characteristics of an intermediate phenomenon that takes place between debris flow and bed load transport are reported and last a new sediment transport equation that is applicable to 1/20-1/4 is proposed. Concerning these studies some experiments were carried out with a laboratory flume. These results are expected to be applied to estimate the processes of debris flow stopping and reerosion.
Slope failure is the phenomenon which take place in three dimensional space, essentially. Therefore it is necessary to take into consideration not only the plane or two-dimensional informations which are easily obtained by topographical maps or aerial photographs but also the knowledge of vertical direction which are obtained only by field investigation. This paper intend to consider the depth of slip surface that have not been too much studied hitherto. In order to achive this purpose, trench cut survey were carried at the mountain slopes in a selected test field composed of granite and soil horizon was determined by the observation of those cut faces, field investigations such as the measurement of seismic wave velocity and soil laboratory test. These trenches were tutted at failure slopes and non-failure slopes. The layer in which slip surface existed was determined by the comparison of these soil horizons. In this papar, it is proposed that this determination is done by using the simple dynamic cone penetrometer. The boundary value that it take place failure or not, is about Ñ10=12.6. This value means that it needs 12.6 blows of 5kg weight, 50 cm height, to penetrate 10 cm. Table 1 show the classification of soil horizon for mountain slope failure caused by heavy rainfall.