HR: 1340h
AN: H53C-1283    [Abstracts]
TI: Erosion Processes of Streambed in the Channelized River Draining Into the Kushiro Mire, Hokkaido, Northern Japan
AU: * Mizugaki, S
EM: mizu@for.agr.hokudai.ac.jp
AF: Graduate School of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-Ku, Sapporo, 060-8589 Japan
AU: Yoshida, K
EM: kiwamu@bc5.so-net.ne.jp
AF: Graduate School of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-Ku, Sapporo, 060-8589 Japan
AU: Kojima, Y
EM: kojima@dogi.co.jp
AF: Hokkaido Gijutsu Consultants Inc., Naebo-Cho 4-2-8, Higashi-Ku, Sapporo, 065-0043 Japan
AU: Araya, T
EM: arayat@for.agr.hokudai.ac.jp
AF: Graduate School of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-Ku, Sapporo, 060-8589 Japan
AB: In Japan, the wetlands have shrunk markedly since 1950s due to land-use development from wetland to urban and agricultural land. Rapid sedimentation in the Kushiro Mire, Hokkaido, northern Japan, was caused by extensive land-use development and stream channel rationalization during the 1960s and 1970s. In the Kuchoro River catchment, draining into the Kushiro Mire, the meandering stream was channelized in the mid- and downstream associated with land-use development between 1966 and 1980. Prominent degradation of a streambed due to channelization has occurred over 2 km in the midstream since channelization was finished. Bare slope has occurred due to streambed degradation, and produced fine sediment through the freeze-thaw process in late fall season. Following snowmelt and/or typhoon flood events in spring and summer season could transport fine sediment on the bare slope into the wetland. During a flood event, stream flow eroded the streambed laterally and vertically, resulting in the overhang of riverbank and the dropping down the clods into the stream. These erosion processes has occurred and produced the sediment of 7500 m3/year in average between 2000 and 2003. The upstream portion of a channelized reach is often degraded because of high flow velocities associated with a steeper streambed. On the other hand, the annual sediment production on the streamside bare slopes in the mountain area was measured by erosion pins and estimated as 4500 m3/year. Thus, the reach of streambed degradation is considered a major point-source of suspended sediment in the Kuchoro River catchment for the past 20 years, leading to the recent rapid sedimentation in the marginal area of the wetland.
DE: 1803 Anthropogenic effects
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1886 Weathering (1625)
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting