滋賀県犬上川下流部における河口部掘削後の河床低下と堆積物の段丘化

概要

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Clear downward erosion has occurred at the lower reach of the Inukami River after excavation of the river mouth delta in 1992 and 1993, forming terraced gravel bars on which trees have been invaded. Comparison between longitudinal profiles of the river-bed in 2001 and 2006 showed that clear sedimentation had occurred at the river mouth during this period, whereas downward erosion still had progressed at the lower reach. Lateral profile at the lower reach in 2006 revealed that two new terraced gravel bars had been formed since 2001. Dating of the sediments of these two new terraced bars using dendrochronological method and date of production of buried wastes showed that the lower and higher terraced sediment was deposited from 1997 to 1998 and from 2001 and 2004, respectively. These facts indicate that the river-bed of the lower reach is still degrading forming new terraced bars, and the sediment eroded from the lower reach is deposited at the river mouth area.
2009-07-25