シラス地域の水文地形とシラス斜面崖錐部の崩壊

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In southern Kyushu, Japan, covered with volcaniclastic materials, landslide and debris flow disasters have occurred frequently during rainy and typhoon seasons. Recently, some types of landslide caused by groundwater have sometimes occurred. One type is landslide of talus slope at the head of the valley scarred on the Shirasu (pyroclastic flow deposits) plateau. In this paper, the mechanism of this landslide, the geological and hydrogeomorphological characteristics of the landslide slope sites, and the possibility of predicting the potential landslide sites are examined based on field study. The results are summarized as follow: (1) The landslides of talus slope at the valley head occur in the Shirasu valleys with a certain drainage area of groundwater. The low water discharge in the Shirasu valley is proportional to the drainage area of groundwater. Therefore, the low water discharge serves as an effective index to predict high potential sites for landslide of talus slope at the head of the Shirasu valley. (2) The groundwater in the talus slope at the valley head is supplied from storm waters infiltrated through the Shirasu plateau. The groundwater level in the talus slope responds to storms in a few hours. This rapid flow of groundwater is mainly attributed to the pipe flow in the plateau. (3) On the other hand, there is also a late flow of groundwater which responds to storms after several months or more. This late flow of groundwater is mainly attributed to the matrix flow in the plateau. If the late flow and the rapid flow of groundwater overlap, the groundwater level in the talus slope will become very high and the potential for the landslide will increase.
2002-10-25

シラス地域の水文地形とシラス斜面崖錐部の崩壊

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