A new geophone device for understanding environmental impacts caused by gravel bedload during artificial floods
A new geophone device for understanding environmental impacts caused by gravel bedload during artificial floods
复制标题
一种新的地震检波器装置，用于了解人工洪水期间砾石沉积物造成的环境影响
DOI：
10.1002/2016wr019726
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发表时间：
2017
影响因子：
5.4
通讯作者：
Tsuboshita K.
中科院分区：
文献类型：
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作者：
subaki R.;Kawahara Y.;Zhang X.;Tsuboshita K.
为了评估小洪水期间砾石推移质对卵石床河流中附着藻类和水生植物的去除作用，我们提出了一种用于测量非均匀尺寸砾石的局部推移质的地震检波器类型方法。由于在我们的研究过程中，集中事件的峰值流量有限，大部分床料（此处为鹅卵石）是不动的，只有一小部分床料（沙子和砾石）预计将在我们分析的冲洗流期间运输。我们开发的装置尺寸相当于固定床料，形状类似于现场的床料（圆形鹅卵石）。该仪器的设计可以避免安装过程中河床微地形的干扰和洪水期间的局部推移质运输。为了建立一种估算冲击碎石粒径的经验算法，进行了水槽试验，并讨论了与粒径估算有关的不确定性。所提出的方法被用来量化卵石床河流冲刷过程中的砾石推移质。我们还讨论了冲刷过程中测量的砾石推移质对去除附着藻类（叶绿素a密度降低37%）和水生植物（单位面积干质量降低38%）的贡献。根据测量的砾石推移质的时间变化，我们还提出了由在不动的较大沉积物上迁移的细沉积物部分组成的床形的传播，以及对附着藻类去除的细沉积物波传播的影响。
To assess the contribution of gravel bedload on the removal of attached‐algae and aquatic plants from a cobble‐bed river during small floods, we propose a geophone type method for measuring the local bedload of non‐uniform sized gravel. Due to limited peak discharge for focused events during our study, a large fraction of bed material (here cobbles) was immobile and only a small fraction of bed material (sand and gravel) was expected to be transported during the flushing flows we analyzed. The device we developed has a size equivalent to immobile bed material and a shape similar to bed material (rounded cobbles) at the site. The instrument's design allows avoidance of disturbances in river bed micro‐topography during installation and local bedload transport during floods. A flume experiment was conducted in order to establish an empirical algorithm for estimating the diameter of impacted gravel, and uncertainty related to diameter estimation is discussed. The proposed method was utilized to quantify gravel bedload in a cobble‐bed river during flushing flows. We also discuss the contribution of measured gravel bedload during flushing flows on the removal of attached‐algae (up to a 37% reduction in chlorophyll‐a density) and aquatic plants (a reduction of 38% in dry mass per area). Based on time variation for the measured gravel bedload, we also suggest the propagation of a bed‐form composed of the fine sediment fraction migrating on immobile larger sediment and implications for the propagation of the fine sediment wave for attached‐algae removal.