HR: 14:45h
AN: H43A-04    [Abstracts]
TI: Hillslope-channel sediment linkages in steep forested catchments: sources to transport
AU: * KAMEI, R
EM: 01583_kamei@ing-life.co.jp
AF: Slope Conservation Section Geohazards Division Disaster Prevention Research Institute Kyoto University, Gokasho, Uji, Kyoto, 611-011, Japan
AU: Sidle, R C
EM: sidle@slope.dpri.kyoto-u.ac.jp
AF: Slope Conservation Section Geohazards Division Disaster Prevention Research Institute Kyoto University, Gokasho, Uji, Kyoto, 611-011, Japan
AU: IMAIZUMI, F
EM: imaizumi@sakura.cc.tsukuba.ac.jp
AF: Graduate School of Life and Environmental Sciences, University of Tsukuba , 1621-2 Ikawa, Aoi, Shizuoka, 428-0504, Japan
AB: Sources of eroded sediment and their transport were investigated in four headwater streams with different landslide histories in Nara, Japan, to establish relationships between sediment yield and sediment storage for different channel characteristics and to determine the connectivity of sediment sources on the hillslope with bedload transport. Two of the streams experienced debris flows in 2004; one of these retained a large amount of debris flow sediment (187.2 m3), while the other channel was flushed of most sediment (12.5 m3). Another stream impacted by a debris flow in 1989 retained 253.5 m3 of sediment. Both bedload transport and yield strongly depend on sediment storage in the catchments. The two streams in which large quantities of debris flow sediment were stored produced greater than one order of magnitude more bedload sediment than the two streams where less sediment was stored (12.5 and 79.1 m3, respectively). Bedload transport in the system affected by the older debris flow (1989) was characterized by partial mobility during most storms, while the system affected by the 2004 debris flow was characterized by equal mobility. In both catchments, grain-sizes of bedload sediment were characterized by similar or higher rates of finer materials compared with in- and near- channel deposits. Because eroded bank sediment is relatively fine, it is likely transported rapidly through the fluvial system, whereas coarser landslide sediment and sediment from uprooted trees are may move more slowly as bedload sediment once delivered to the channel. Episodic mass wasting appears to constitute very important inputs in these headwater streams and may greatly alter bedload transport. Sediment source-transport linkages must be understood to assess land use impacts in catchments.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1810 Debris flow and landslides
DE: 1815 Erosion
DE: 1861 Sedimentation (4863)
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: 2007 Joint Assembly