River processes after rapid valley-filling due to large landslides |
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| Authors: | Hiroshi Shimazu Takashi Oguchi |
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| Institution: | (1) Department of Geography, Kanazawa University, 920-11 Kanazawa, Japan;(2) Department of Geography, University of Tokyo, 113 Tokyo, Japan |
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| Abstract: | A three-stage model is proposed to describe river processes after rapid valley-filling due to large landslides, based on surveys on the Shirayuki river basin in northeast Japan. At Stage I slightly entrenched debris avalanche deposits get covered with fluvial sediments. At Stage II the river along the upper reaches deeply cuts into fill deposits while fan aggradation occurs along the lower reaches. At Stage III river incision occurs along all the courses. This sequence of river processes reflects the changing amounts of post-landslide debris supply from the landslide scar and river banks. The three-stage model is also applicable to other examples of post-landslide river processes, although some lack the Stage I. Morphometric analyses suggest that the presence or absence of the Stage I depends on the ratio of debris supply from the landslide scar to river competence of sediment delivery. |
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