| Project/Area Number |
07456065
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
林学
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
NAKAMURA Futoshi HOKKAIDO UNIV., FAC.OF AGR., ASSOCIATE PROF., 農学部 (90172436)
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| Co-Investigator(Kenkyū-buntansha) |
KURIYAMA Kouichi HOKKAIDO UNIV., FAC.OF AGR., INSTRUCTOR, 農学部・助教授, 助手 (50261334)
YAJIMA Takashi HOKKAIDO UNIV., FAC.OF AGR., ASSOCIATE PROF., 農学部, 助教授 (90142702)
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| Project Period (FY) |
1995 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥4,500,000 (Direct Cost: ¥4,500,000)
Fiscal Year 1997: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1995: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Keywords | Wetland / Kushiro Marsh / Land-use / Wash-load / Suspended sediment / Cs-137 / Wetland vegetation / River regulation / ヤチダモ / ウォッシュロード / ハンノキ / 濁度 / 流域保全 |
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| Research Abstract |
Wetlands' effects on hydrology, water quality, and wildlife habitat are internationally recognized. We examined the influences of channelization on discharge of suspended sediment and wetland vegetation in Hokkaido, northern Japan. The impact of river channelization was confirmed not only by the sediment gudgets but also by river aggradation or degradation lafter the channelization and by the resultant vegetational changes. The budgets of suspended sediment demonstrated that wash load was the predominant component accounting for 95% of the total suspended load delivered into the wetland. This suspended sediment was primarily transported into the wetland by floding associated with the heavy rainfall. 25% of the wash load and 75% of the suspended bed material load were deposited in the channelized reach, which produced aggradation of about 2 m at the end of the reach. A shorting of the length of the channel, due to channelization of a meandering river, steepened the slope and enhanced the stream power to transport sediment. This steepening shifted the depositional zones of fine sediment 5km downstream and aggraded the riverbed. The aggradation reduced the carrying capacity of the channel and caused sediment ladened water to flood over the wetlands. the fine sediment accumulated on the wetlands gradually altered the edaphic conditions and wetland bvegetation. Salix spp.and Artemisis princeps dominate the sites representing a high water-level fluctuation and high total nitrogen, and low redox potential of wetlands' ground water. These sites are more evidence indicating taht the present condition is far different from normal. Orifinal vegetation such as sedges and Alunus japonica sere disappearing from the adjacent areas of the river channel and were being replaced by willow trees.
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