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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Estimating the timescale of fluvial response to anthropogenic disturbance using two generations of dams on the South River, Massachusetts, USA
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Estimating the timescale of fluvial response to anthropogenic disturbance using two generations of dams on the South River, Massachusetts, USA

机译：使用两代水坝在南河上，美国马萨诸塞州使用两代水坝来估算氟尿对人为干扰的时间尺度

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Centuries-long intensive land-use change in the north-eastern United States provides the opportunity to study the timescale of geomorphic response to anthropogenic disturbances. In this region, forest-clearing and agricultural practices following EuroAmerican settlement led to deposition of legacy sediment along valley bottoms, including behind mill dams. The South River in western Massachusetts experienced two generations of damming, beginning with mill dams up to 6-m high in the eighteenth-nineteenth century, and followed by construction of the Conway Electric Dam (CED), a 17-m-tall hydroelectric dam near the watershed outlet in 1906. We use the mercury (Hg) concentration in upstream deposits along the South River to constrain the magnitude, source, and timing of inputs to the CED impoundment. Based on cesium-137 (Cs-137) chronology and results from a sediment mixing model, remobilized legacy sediment comprised74-35+26% of the sediment load in the South River prior to 1954; thereafter, from 1954 to 1980s, erosion from glacial deposits likely dominated (63 +/- 14%), but with legacy sediments still a substantial source (37 +/- 14%). We also use the CED reservoir deposits to estimate sediment yield through time, and find it decreased after 1952. These results are consistent with high rates of mobilization of legacy sediment as historic dams breached in the early twentieth century, and suggest rapid initial response to channel incision, followed by a long decay in the second half of the century, that is likely dependent on large flood events to access legacy sediment stored in banks. Identifying sources of sediment in a watershed and quantifying erosion rates can help to guide river restoration practices. Our findings suggest a short fluvial recovery time from the eighteenth-nineteenth century to perturbation during the first half of the twentieth century, with subsequent return to a dominant long-term signal from erosion of glacial deposits, with anthropogenic sediment persisting as a secondary source. (c) 2020 John Wiley & Sons, Ltd.
机译：百分纪的长期密集的土地使用在美国东北部门提供了机会研究对人为紊乱的几制反应的时间。在该地区，欧洲欧亚人沉降后的森林清算和农业实践导致沿谷底部沉积遗留沉积物，包括磨机后面。马萨诸塞州西部的南部河流经历了两代渔民，从磨机坝开始于十九世纪高达6-M高，随后建造了一个17平方米的水电大坝（CED）在1906年靠近流域出口。我们在南河上使用上游沉积物中的汞（Hg）浓度来限制输入对CED蓄积的输入的幅度，来源和时间。基于Cesium-137（CS-137）的年表和沉积物混合模型的结果，在1954年之前的南河中的沉积物沉积物的重新化遗留沉积物;此后，从1954年到20世纪80年代，冰川沉积物的侵蚀可能占主导地位（63 +/- 14％），但遗产沉积物仍然是一个实质性的来源（37 +/- 14％）。我们还使用CED储库存款来估计沉积物产量通过时间，并在1952年之后发现它减少。这些结果与二十世纪初违反的历史水坝的遗产沉积物的高速度一致，并建议对渠道的快速初始回应切口，其次是本世纪下半叶的较长衰减，这可能依赖大型洪水事件来访问存储在银行的遗产沉积物。识别流域和量化侵蚀利率中的沉积物来源可以有助于引导河流修复实践。我们的研究结果表明，在二十世纪上半年的十八世纪到第十九世纪的扰动短暂的河流恢复时间，随后返回到冰川沉积物的侵蚀的主要长期信号，随后沉积物持续为二级来源。 （c）2020 John Wiley＆Sons，Ltd。

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