POST-VOLCANIC EROSION RATES OF SHOMYO FALLS IN TATEYAMA, CENTRAL JAPAN
Post-eruptive fluvial erosion of welded pyroclastic flow deposits often depends on the recession of waterfalls because of their rapid erosion involved. We examine the recession rate of Shomyo Falls, which consists of Pleistocene welded pyroclastic flow deposits in Tateyama, north-central Japan. The mean recession rate of the waterfall obtained from lithological and topographical evidences is 0.08-0.15 m/a for 100000 a. However, the recession rate estimated by means of an empirical equation comprising physical parameters of erosive force and bedrock resistance is 0.006-0.011 m/a with small uncertainties. The discrepancy between the geology-based and equation-based recession rates indicates that some factors, not taken account of in the equation, significantly influence the recession rate. We suggest that a factor in the rapid erosion of the waterfall is a large amount of transported sediment acting as abrasive material, which is supplied from high mountains in the watershed above the waterfall.
Document Type: Research Article
Affiliations: 1: Geoenvironmental Sciences, Graduate School of Life and Environmental Sciences, University of Tsukuba, Japan 2: Department of Environment Systems, Graduate School of Frontier Sciences, The University of Tokyo, Japan
Publication date: March 1, 2008