玄手川水路底改修に伴う水生植物の回復 Restoration of waterweeds in a remodeled channel

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著者

    • 広瀬 慎一 HIROSE Shinichi
    • 短期大学部農業技術学科 Section of Agricultural Engineering, Department of Agricultural Technology, College of Technology

抄録

従来の河川や水路の改修においては,水管理や江ザライの省力化を目的として,コンクリートを多用した底張りや護岸が行われてきた。そのため,改修工事を行なった水路で,水生動植物などの野生生物が減少・絶滅するという現象が起き,生物の多様性が危ぶまれるようになった。しかし近年,自然環境に対する社会的関心が高まり,治水・利水等の機能の維持と,河川・水路のもつ自然環境を調和させた生物のすみ易い近自然工法が注目されている。ところが,近自然工法が適用されても,施工後その効果の追跡調査が十分行われていないので,その工法が適正であったかどうかは数量的にはわからない場合が多い。本研究では,玄手川の水路底が水環境整備事業によって新しい工法で施工された後,従来の水草がどのような経過をたどってどれだけ再生したかを明らかにした。

The river Gente is a 3,000m-long river used as a drainage channel and flows north down the northernmost part of the Shogawa alluvial fan. The stream is fairly clean thanks to an abundant supply of seepage water welling up out of the underground and abounds in aquatic plants and animals such as Tomiyo and Sparganium, the latter of which is already listed as a semi-endangered species in the red data book. The revetments of the river were once renovated using dry concrete blocks (1970-1972) but the soil riverbed was left untouched, as was usual with the renovation of a drainage channel in those days. Thus waterweeds still grew wild, incurring both a reduction in the drainage performance of the channel and an increase in its M & O cost. This predicament prompted a further renovation of the channel. This time 80% of the riverbed was covered alternately with flat concrete blocks and gravel-filled blocks (1996-2000). This construction design was adopted for the dual purpose of facilitating waterweed control and minimizing damage to aquatic life. I surveyed the effects this riverbed renovation has produced on the ecosystem of this river. In this research, for an indication of the restoration of the aquatic ecosystem I focused on the waterweeds, in which fish nest. 70% of the waterweeds had originally been accounted for by Sparganium, and the rest mainly by five other kinds of waterweeds such as Ranunculus. I found the original ratios of these plants were restoring in about 3 years. And the coverage rate of waterweeds over the riverbed, which had been 67% before the riverbed renovation, was restored in about 4 years. This shows that it takes at most four years after a riverbed renovation for the original state of the waterweeds to be restored on both counts.

収録刊行物

  • 富山県立大学紀要

    富山県立大学紀要 11, 65-75, 2001-03-30

    富山県立大学

各種コード

  • NII論文ID(NAID)
    110000477642
  • NII書誌ID(NCID)
    AN10358595
  • 本文言語コード
    JPN
  • 雑誌種別
    大学紀要
  • ISSN
    09167633
  • NDL 記事登録ID
    5808681
  • NDL 雑誌分類
    ZV1(一般学術誌--一般学術誌・大学紀要)
  • NDL 請求記号
    Z22-1659
  • データ提供元
    NDL  NII-ELS 
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