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Sediment yield from a forested mountain basin in inland Pacific Northwest: Rates, partitioning, and sources

机译：来自内陆太平洋西北地区的森林山地盆地的沉积物产量：利率，分区和来源

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Sediment yield estimates, combined with information regarding sediment sources and partitioning (bedload vs. suspended load), can provide important insights into geomorphic character of the landscape of interest. This study reports such an analysis, conducted in a forested mountain basin in inland Pacific Northwest using reservoir deposits, ground surveys, and repeat LiDAR mapping. Our research generated three key conclusions. First, we estimated mean specific yield of clastic sediment from the study basin during the last century as similar to 51 Mg km(-2) a(-1). In the context of a data compilation from mountain basins in northwestern North America, this value was among the highest for inland basins, and among the lowest when compared with coastal basins. Second, a sediment source analysis provided valuable clues regarding the relative importance of various geomorphic processes operating in the system under study. These findings were consistent with our hypothesis that anthropogenic disturbances may be an important factor that conditions sediment yield from the basin. A mix of quantitative and qualitative evidence suggested that the estimated sediment yield value reflects a transient increase associated with past timber harvest, road construction, and large wood removal. Legacies of these disturbances appear to have the opposite effect on contemporary processes, limiting lateral activity of the channel as well as hillslope-channel connectivity. Third, our partitioning procedure revealed that bedload constituted approximately a third of the total clastic load exported from the basin. This finding suggests that, in this and similar fluvial systems, sediment yield recovery following major geomorphic disturbances could be protracted, as a considerable portion of mobilized sediment that moves as bedload is routed and evacuated from the basin for years or decades after rapid flushing of suspended material. Moreover, this finding indicates that the common assumption that bedload constitutes 10-20% of the total load can lead to underestimation in mountain basins. (C) 2020 Elsevier B.V. All rights reserved.
机译：沉积物收益率估计，与沉积物来源和分区的信息相结合（Boadload与悬浮载），可以为感兴趣的景观的几何特征提供重要的见解。本研究报告了这种分析，在南太平洋西北地区的森林山盆地进行了使用储层沉积物，地面调查和重复激光雷达映射。我们的研究产生了三个关键的结论。首先，我们估计上个世纪中研究盆地的碎片沉积物的平均特异性产量与51mg（-2）A（-1）相似。在北美西北部山区的数据汇编的背景下，内陆盆地的价值是最高的，与沿海盆地相比最低。其次，沉积物源分析提供了有价值的线索，关于在研究中运行的各种地貌过程的相对重要性。这些发现与我们的假设一致，即人为扰动可能是条件从盆地沉积物产量的重要因素。定量和定性证据的混合表明，估计的沉积物产量值反映了与过去的木材收获，道路建设和大型木材去除相关的瞬态增加。这些扰动的遗址似乎对当代工艺产生相反的影响，限制了通道的横向活动以及山坡通道连接。第三，我们的分区程序揭示了床单大约是从盆地出口的总碎片负荷的大约三分之一。这一发现表明，在这种和类似的河流系统中，在主要地貌紊乱之后的沉积物产量恢复可以延伸，作为移动沉积物的相当大部分动员沉积物，在悬浮的快速冲洗之后从盆地沟通和疏散。材料。此外，该发现表明，床单占总载荷的10-20％的共同假设可能导致山盆地低估。 （c）2020 Elsevier B.v.保留所有权利。

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