Self-organization of river channels as a critical filter on climate signals
Self-organization of river channels as a critical filter on climate signals
复制标题
河道的自组织作为气候信号的关键过滤器
作者：
C. Phillips;D. Jerolmack
过滤掉大洪水的影响大洪水似乎应该影响河流的深度和宽度。然而，菲利普斯和杰洛马克认为，基岩河道的自组织减弱了极端降雨事件的影响。从美国各地的河道颗粒河流的河道几何形状表明，较大的洪水对河道几何形状的额外影响非常有限。河道冲刷确实会随着洪水规模的增加而增加，但这种影响在中度洪水中最为明显。这种关系可以解释河流在气候变化中的长期稳定性。《科学》，本期第694页对美国河流的广泛评估表明，在大降雨事件期间，侵蚀和气候变得脱钩。降雨的时空变化被假设为通过河流的侵蚀和泥沙输运来影响景观演变。然而，确定降雨量和河流动力学之间的关系，需要更好地了解洪水和河流的能力，运输泥沙之间的反馈。我们分析了来自美国186条粗粒度河流的通道几何形状和流量记录。我们发现，渠道调整其形状，使洪水略超过临界剪切速度需要运输床沉积物，独立的气候，构造和基岩控制。与洪水相关的流体剪切速度的分布是普遍的，这表明近临界通道的自组织过滤了流量中明显的气候信号。这种效应减弱了极端降雨事件对景观演化的影响。
Filtering out the effect of large floods Large floods should seemingly influence the depth and width of rivers. Phillips and Jerolmack, however, suggest that the self-organization of bedrock river channels blunts the impact of extreme rainfall events. River channel geometries from a wide range of course-grained rivers across the United States show that larger floods have very limited additional impact on channel geometry. River channel sculpting does increase as flood size increases, but the effect is most pronounced for moderate floods. This relationship may explain the long-term stability of rivers across shifts in climate. Science, this issue p. 694 A wide-ranging assessment of rivers in the United States suggests that erosion and climate become decoupled during large rainfall events. Spatial and temporal variations in rainfall are hypothesized to influence landscape evolution through erosion and sediment transport by rivers. However, determining the relation between rainfall and river dynamics requires a greater understanding of the feedbacks between flooding and a river’s capacity to transport sediment. We analyzed channel geometry and stream-flow records from 186 coarse-grained rivers across the United States. We found that channels adjust their shape so that floods slightly exceed the critical shear velocity needed to transport bed sediment, independently of climatic, tectonic, and bedrock controls. The distribution of fluid shear velocity associated with floods is universal, indicating that self-organization of near-critical channels filters the climate signal evident in discharge. This effect blunts the impact of extreme rainfall events on landscape evolution.