The influence of sediment thickness on energy delivery to the bed by bedload impacts
The influence of sediment thickness on energy delivery to the bed by bedload impacts
复制标题
沉积物厚度对通过床载影响向床层输送能量的影响
DOI：
10.1080/09853111.2015.1047195
复制
发表时间：
2016
期刊：
影响因子：
1.5
通讯作者：
J. Bloem
中科院分区：
文献类型：
--
作者：
J. Turowski;J. Bloem
河流基岩的冲刷速率被认为与输送到基岩上的能量成正比。当泥沙颗粒覆盖床层时，它们会减少撞击颗粒传递到床层的能量。在实验室实验中，我们测量了通过增加厚度的沉积物覆盖物传递的能量的衰减。到达床层的能量是覆盖层厚度和覆盖层沉积物粒度的函数。利用一个简单的盖度分布随机模型，将试验结果放大到河段尺度。尽管盖层厚度在给定点对能量传输影响很大，但当整个床层平均时，无盖层区域主导着总的能量传输，当床层的一小部分或中间部分被泥沙覆盖时，通过盖层的部分能量传输可以忽略不计。当很大一部分或整个床层已经被覆盖时，通过床罩的部分能量传递是不可忽略的，但在这种情况下，侵蚀阈值可能变得重要。根据所提供的数据，我们预计沉积物在基岩河道中的面积分布主导着总的能量输送，对于大多数模拟目的，通过沉积层向床的部分能量输送可以忽略不计。
Fluvial bedrock erosion rates due to impacting sediment particles are thought to be proportional to the energy delivered to the bedrock. When sediment particles cover the bed, they reduce the energy transmitted to the bed by an impacting particle. We measured the decline of energy transferred through sediment cover of increasing thickness in laboratory experiments. The energy arriving at the bed is a function both of the cover thickness and the grain size of the covering sediment. Using a simple stochastic model of cover distribution, the experimental results were upscaled to the reach scale. Although cover thickness influences energy delivery heavily at a given point, when averaging over the whole bed, cover-free areas dominate total energy delivery, making partial energy transfer through the cover negligible when a small or intermediate fraction of the bed is covered by sediment. Partial energy delivery through the bed cover is not negligible when a large fraction or the complete bed is already covered, but in this situation, an erosion threshold may become important. On grounds of the presented data, we expect that the areal distribution of sediment in a bedrock channel dominates total energy delivery and that partial energy delivery to the bed through a sediment layer can be neglected for most modelling purposes.