APROBABILISTIC PREDICTION MODEL ON SEDIMENT PRODUCTION IN MOUNTAIN REGION

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It is important to develop a model describing the essential points of usual or unusual sediment production process to estimate precisely the sediment production rate. In this research, taking up the sediment production due to freezing and thawing as a usual event and the slope failure as an unusual event, we have proposed the fundamental models that could provide the probabilistic properties of sediment production if the probability density functions of atmospheric and hydrological variables are introduced into the models. Firstly, we have developed a model for freezing and thawing process on bare slopes. Air temperature, wind velocity and solar radiation are included in the model as the parameters and also slope angle and direction can be considered. Therefore, an advantage of the model is applicable for any slopes in the world where the atmospheric, hydrological and topographical data are available. The validity of the model was verified by comparison between the observation data and the simulation result for Mt. Tanakami and the Takahara river basin. A transformation process from weathered bedrock to soil should be investigated, but this model could be developed as an evaluation model for the influence of the global warming on the sediment production. Secondly, we have proposed a numerical model on slope failure considering the soil pipes inside of slopes. Using the model, we discussed the influence of soil pipes and the piles clogging on the occurrence of slope failure. Also, we have investigated the characteristics of slope failure for two different types of slope, namely, two slopes sustained mainly by cohesion force or friction force. For the former, a long collapse with much water content occurs, and for the latter, a phased slope failure composed of short collapses take place.