Hydrology of Braided River Systems

富福拉辫状河是复杂的动力系统，由多个不稳定的冲积河道组成，这些河道围绕沙洲和岛屿分割和重新连接，并频繁地在河流的辫状平原上迁徙。尽管辫状河在低地地区并不常见，但在高纬度和沉积迅速的地区占主导地位。在阿拉斯加和太平洋西北部等地区，必须在这些地区修建桥梁和管道，这是一个重大的管理挑战。此外，辫状河冲积是重要的水、油、气、煤、砂、砾石和重矿物储集层。它们的不稳定性和机会性的流态使得对辫状河的预测变得非常困难。最近的进展提出了几种分析这些复杂动力系统的新方法。现在清楚的是，辫状河流表现出空间和动态(时间-空间)尺度；即，在适当的重新密封下，在平面几何和演变方面，河网的一小部分在统计上与较大部分相似。这一观察打开了统计预测罕见的高震级通道漂移的可能性，从较小尺度上容易获得的较低震级但更频繁的事件的记录。同样清楚的是，至少可以根据河流动力学的简化模型来预测辫状河的这些系统尺度或“涌现”特性中的一部分。最后，最近的实验工作表明，辫状河的平面形态和动力学可以受到适量的岸边植被的显著影响，甚至有可能仅通过植被效应将辫状河转变为曲流河。我们建议将这三条研究线结合起来，专注于以下基本问题：(1)将辫状河的尺度分析扩展到第三(垂直)维，即水流、流速、河床高程和泥沙通量的尺度，这对洪水、现代河流的冲刷和流动性以及古代沉积物的地层结构的统计预测具有重要意义；(2)以水文尺度结果作为模型尺度，对现有的辫状河模型进行测试和改进；以及(3)研究植被对辫状河的影响，重点研究水流和植被的重复循环如何导致辫状河流入少数明确界定的河道，打破尺度，可能导致第一个真正自我再生的曲流河的发展。

0207556FoufoulaBraided rivers are complex dynamical systems comprising multiple unstable alluvial channels that divide and rejoin around bars and islands and migrate frequently across the river's braidplain. Although not common in lowland areas, braided rivers are dominant at high latitudes and in areas with rapid sedimentation. They represent a major management challenge in areas such as Alaska and the Pacific Northwest where bridges and pipelines must be built across them. In addition, the alluvial deposits of braided rivers are important reservoirs of water, oil, gas, coal, sand, gravel and heavy minerals. Their instability and opportunistic flow patterns make prediction of braided rivers extremely difficult.Recent advances have suggested several new ways of analyzing these complex dynamical systems. It is now clear that braided rivers exhibit both spatial and dynamic (time-space) scaling; i.e. a small part of the river network is statistically similar to a larger part, in terms of planform geometry and evolution, under appropriate resealing. This observation opens up the possibility of statistical prediction of rare, high-magnitude channel shifts from readily obtainable records of lower magnitude but more frequent events occurring at smaller scales. It is also clear that at least some of these system-scaling or "emergent" properties of braided rivers can be predicted on the basis of simplified models of the stream dynamics. Finally, recent experimental work has illustrated that the planform pattern and dynamics of braided rivers can be dramatically affected by modest amounts of bank vegetation; it may even be possible to convert a braided to meandering river by vegetation effects alone.We propose to unite and build on these three lines of research, focusing on the following basic issues: (1) extension of scaling analysis in braided rivers to the third (vertical) dimension, i.e., scaling of flows, velocities, bed elevation and sediment flux, with implications for statistical prediction of floods, scour and mobility in modern rivers, and stratigraphic architecture in ancient deposits; (2) testing and refinement of existing braided-river models using hydrologic scaling results as a model metric; and (3) study of the effects of vegetation on braided rivers, focusing on how repeated cycles of flow and vegetation can lead to the 'regularization' of braided-river flows into a small number of well defined channels, breaking the scaling and perhaps leading to the development of the first truly self-regenerating meanders.