Flow detachment by concentrated flow on smooth and irregular beds
Flow detachment by concentrated flow on smooth and irregular beds
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DOI：
10.2136/sssaj2002.1475
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发表时间：
2002-09-01
影响因子：
2.9
通讯作者：
Govers, G
中科院分区：
文献类型：
--
作者：
Giménez, R;Govers, G
从历史上看，主要使用具有光滑表面的小样本来研究由坡面流引起的土壤剥离。这可能是一个问题，在何种程度上从这样的实验信息可以应用于预测流动分离的积极侵蚀细沟的特点是粗糙不规则的床面。为了评估粗糙和光滑河床上的水流分离是如何相关的，进行了两种类型的实验室实验：自然细沟实验，细沟可以自由发展;和小样本实验，使用具有光滑表面的小盒子。在这两种类型的实验中，土壤条件尽可能保持恒定。在每个实验过程中详细记录水流水力学和泥沙负荷。我们的实验表明，单位长度剪切力和剪切应力是细沟中最通用的剥离预测因子（即，这些变量与土壤剥离之间的关系与河床几何形状无关）。其他水力变量也可以成功地与给定床类型（光滑或粗糙）上的流动分离相关，但它们不能适应床几何形状变化的影响。事实上，总剪切应力控制流动分离，而不是颗粒剪切应力或单位流功率意味着沉积物分离和沉积物输运之间的耦合比目前假设的更复杂。使用基于单位长度的水力参数的脱离预测方法可以允许比预测器更准确和更简单的方式来估计细沟中的沉积物脱离，所述预测器需要流宽的先验计算。
Historically, soil detachment by overland flow has mainly been studied using small samples with smooth surfaces. It may be questioned to what extent information from such experiments can be applied to predict flow detachment in actively eroding rills which are characterized by rough irregular bed surfaces. To evaluate how flow detachment on rough and smooth beds are related, two types of laboratory experiments were carried out: natural rill experiments, where a rill could freely develop; and small sample experiments, where small boxes with smooth surface were used. Soil conditions in both types of experiments were kept as constant as possible. Flow hydraulics and sediment load were recorded in detail during each experiment. Our experiments show that unit length shear force and shear stress are the most universal detachment predictor in rills (i.e., the relationship between these variables and soil detachment is independent of bed geometry). Other hydraulic variables can also be successfully related to flow detachment on a given bed type (smooth or rough), but they cannot accommodate for the effect of changing bed geometry. The fact that total shear stress controls flow detachment rather than grain shear stress or unit stream power implies that the coupling between sediment detachment and sediment transport is more complex than is presently assumed. A detachment prediction approach using hydraulic parameters based on unit length may allow a more accurate and simpler way to estimate sediment detachment in rills than a predictor, which needs an a priori calculation of flow width.