History, Physical Effects, and Management Implications of Large Organic Debris in Western Oregon Streams

Frederick John Swanson · George W. Lienkaemper · James R. Sedell

1976年1月 · Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station

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"Large organic debris has historically been an important element in small mountain streams of the Pacific Northwest. The debris serves to slow the movement of water and inorganic and fine organic matter through the channel. Debris may remain in the channel for decades or longer, and tends to stabilize some sections of a streambed and stream banks while destabilizing other areas. The combination of clear cutting and the complete removal of large debris in a channel may deprive a stream of this natural feature of streams for a century or longer. The consequences are likely to be downcutting and channelization" of the stream, accelerated transport of fine organic and inorganic sediment, and a possible decrease in biological productivity of the stream ecosystem. Therefore, stream debris management during logging operations should include leaving undisturbed the natural, stable organic debris in the channel.‍?‍?The principal factors controlling the concentration, stability, and functions of stream debris are the history and condition of the surrounding timber stand, flushing history of the channel, stability and abundance of bedload material, steepness of the channel and adjacent hillslopes, and slope stability in the drainage. Because of this complexity, each stream presents a unique situation, which should be inspected in the field and considered on an individual basis before a debris management decision is made."