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北海道南部の山地小河川における細粒土砂の堆積と浮き石および河床内の透水性に関する研究

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Title: 北海道南部の山地小河川における細粒土砂の堆積と浮き石および河床内の透水性に関する研究
Other Titles: Hydraulic conductivity of substrate and openwork gravel rate associated with fine sediment depositon in mountain streams, southern Hokkaido
Authors: 村上, まり恵1 Browse this author
山田, 浩之2 Browse this author →KAKEN DB
中村, 太士3 Browse this author →KAKEN DB
Authors(alt): MURAKAMI, Marie1
YAMADA, Hiroyuki2
NAKAMURA, Futoshi3
Keywords: fine sediment
frozen core technique
hydraulic conductivity
openword gravel
packer test
Issue Date: 2001
Publisher: 応用生態工学会
Journal Title: Ecology and Civil Engineering
Journal Title(alt): 応用生態工学
Volume: 4
Issue: 2
Start Page: 109
End Page: 120
Publisher DOI: 10.3825/ece.4.109
Abstract: 細粒土砂(<2mm)の堆積が浮き石割合,透水性に与える影響を検討するため,北海道南西部の遊楽部川流域と貫気別川流域の底質が異なる5つの山地小河川を対象として,粒度組成と浮き石割合および透水係数の調査を行った.また,これらの河川間の違いを明らかにした上で,各河川の土地利用の特徴について考察した.なお,流水中の河床における細粒土砂の採取には凍結コア法を用い,透水係数の計測には原位置透水試験のパッカー法を適用した. 浮き石割合および透水係数は,平均粒径,歪度,尖度と強い相関が見られ,また細粒土砂の重量割合と負の相関が得られた.なかでも,粒径0.125-1,0mmの重量百分率と最も強い負の相関が得られた.これらのことから,細粒土砂の堆積により,浮き石割合および透水係数が低下することが定量的に明らかになった.また,浮き石割合の減少により透水係数が低下することが得られた.一方,河川間において,細粒土砂の重量百分率,浮き石割合,透水係数に違いが認められ,細粒土砂量が多く,透水係数や浮き石割合が低い河川は,農地率の高い河川であった.農地開発により表土流出や河岸崩壊が生じ,土砂生産量が増加すると報告されていることから,農地率が高い河川では,そのような影響が底質に現れたと考えられた.また,細粒土砂を多く含む河床では,出水によるフラッシュ・アウトがない場合,細粒土砂の堆積が進行し,河川生物相に及ぼす影響が大きいことが予想された. 本研究で用いた凍結コア法およびパッカー法は,流水中の細粒土砂の採取および透水係数の測定方法として有効であった,今後,河川環境の保全を考える際,これらの方法を活用して細粒土砂に関する知見を深め,河床への堆積過程さらに堆積防止方法を検討する必要がある.
Abstract: The fine sediment (<2 mm) effects on percentage of openwork gravel and hydraulic conductivity were studied at 5 small catchments in southwestern Hokkaido, Japan in 1999. We also examined the influence of land use on substrate and hydraulic conductivity. Bed material was sampled using the frozen core technique and hydraulic conductivity was measured using the packer test. The percentage of openwork gravel and hydraulic conductivity decreased with an increase in proportion of fine sediment. Especially the weight percentage of 0.125 to 1.0 mm showed the most negative correlations with these parameters, which indicates that fine sediment filling the interstitial space of gravel bed is responsible to the decreases in these parameters. The stream containing great amount of fine sediment had extensive agricultural development in its catchment area. Thus these substrata differences among the streams were attributable to the surface soil erosion and bank erosion at agricultural fields. Fine sediment progressively accumulated in streambed materials under normal flow conditions, resulting in a decrease in openwork gravels and hydraulic conductivity. Losing the interstitial space of gravel bed will have detrimental effects on benthic fish and invertebrate and other aquatic biota that require these habitats in their life cycles. In order to maintain healthy stream ecosystem, we need to pay more at-tention on the conditions of fine sediment and bed materials, and to seek effective meas-ures to prevent fine sediment production and deposition. The sampling methods applied in this study were proved to be useful to investigate fine sediment and hydraulic conductivity of the bed materials.
Rights: © 応用生態工学会
Type: article
URI: http://hdl.handle.net/2115/68549
Appears in Collections:農学院・農学研究院 (Graduate School of Agriculture / Faculty of Agriculture) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 山田 浩之

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