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Hydrologic, geomorphic, and stratigraphic controls on suspended sediment transport dynamics, Big Harris Creek restoration site, North Carolina, USA
Anthropocene ( IF 3.3 ) Pub Date : 2019-01-03 , DOI: 10.1016/j.ancene.2018.12.002
Jerry R. Miller , Kelly Ferri , David Grow , Lionel Villarroel

Water quality monitoring records were combined with geomorphic and stratigraphic data to determine the controls on suspended sediment transport dynamics within the headwaters of Big Harris Creek, the site of one of the largest stream restoration projects in North Carolina, USA. Land-use change associated with European settlement resulted in spatially variable geomorphic responses that produced reaches possessing semi-homogeneous landforms and processes, referred to as process zones. Downstream, process zones were dominated by entrenched channels possessing banks characterized by sandy post-settlement deposits that overlie finer-grained pre-settlement deposits. Spatial variations in the resulting process zones strongly influenced modern suspended sediment concentrations (SSC) and loads in the catchment, which are among the highest reported for the southeastern United States. The source and transport dynamics of suspended sediment differed between low magnitude floods (characterized by minimal changes in water level elevations) and moderate to high magnitude floods. Low magnitude floods were characterized by SSCs that varied over several orders of magnitude, and that were unrelated to flow conditions. Precipitation, during these events, rapidly mobilization fine-grained pre-settlement deposits associated with bank failures and cattle crossings along entrenched alluvial channels. Moderate to high magnitude floods within larger tributary basins exhibited more systematic discharge-SSC relationships. Suspended sediment transport was dominated by sand-sized particles derived from post-settlement legacy sediments eroded from the channel banks and headwater gullies. The observed temporal and spatial differences in SSC between low and moderate to high magnitude floods complicates the quantification of water quality, and shows that comparisons of water quality before and following the implementation of restoration projects need to differentiate between distinct populations of suspended sediment transport.



中文翻译:

悬浮泥沙运移动力学的水文,地貌和地层控制,美国北卡罗来纳州大哈里斯克里克修复基地

将水质监测记录与地貌和地层数据相结合,以确定对大哈里斯河上游(美国北卡罗来纳州最大的河流修复项目之一)的源头中悬浮泥沙输送动力学的控制。与欧洲定居相关的土地利用变化导致空间变异的地貌响应,所产生的河段具有半均质的地貌和过程,称为过程区。在下游,加工区被根深蒂固的河床所支配,河床中的河床具有沙质的沉淀后沉积物,这些沉淀物覆盖在较细颗粒的沉淀前沉积物上。最终工艺区域的空间变化强烈影响了现代悬浮沉积物浓度(SSC)和流域负荷,这是美国东南部报告的最高记录之一。悬浮泥沙的来源和运移动力学在低强度洪水(以水位高度的最小变化为特征)和中高强度洪水之间有所不同。低强度洪水的特征在于南南合作区的变化幅度达几个数量级,并且与水流状况无关。在这些事件期间,降水迅速动员了与银行倒闭和沿盘uv的冲积通道穿越牛群相关的细颗粒的沉淀前沉积物。较大支流盆地内的中度至高洪涝表现出更系统的流量-SSC关系。悬浮的泥沙运移以沙粒大小的颗粒为主,这些颗粒来自沉降后从河道堤岸和上游水源冲刷的沉积物中。在低洪灾和中洪灾与高洪灾之间观测到的南南合作时空差异使水质量化变得复杂,并表明,在实施修复项目前后,对水质进行比较需要区分悬浮泥沙输送的不同种群。

更新日期:2019-01-03
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