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.

中文翻译：

---

沉积物厚度对床负荷影响下输送到床的能量的影响

由于撞击沉积物颗粒而导致的河流基岩侵蚀速率被认为与传递到基岩的能量成正比。当沉积物颗粒覆盖床层时，它们会减少撞击颗粒传递到床层的能量。我们在实验室实验中测量了通过增加厚度的沉积物覆盖层传递的能量的下降。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。使用覆盖分布的简单随机模型，将实验结果放大到覆盖范围。尽管覆盖层厚度对给定点的能量传输影响很大，但在对整个床进行平均时，无覆盖区域主导了总能量传输，当床的一小部分或中间部分被沉积物覆盖时，通过覆盖层的部分能量传递可以忽略不计。当大部分或整个床层已经被覆盖时，通过床层覆盖的部分能量传递是不可忽略的，但在这种情况下，侵蚀阈值可能变得很重要。根据所提供的数据，我们预计基岩通道中沉积物的区域分布主导了总能量传递，并且对于大多数建模目的，通过沉积物层向床传递的部分能量可以忽略。