Hydrology of Braided River Systems

0207556 Foufoula辫状河是一个复杂的动力系统，由多个不稳定的冲积河道组成，这些河道在沙洲和岛屿周围分开和重新汇合，并经常穿越河流的辫状平原。 尽管在低地地区不常见，但辫状河在高纬度地区和快速沉积的地区占主导地位。 在阿拉斯加和太平洋西北部等地区，它们是一个重大的管理挑战，必须在这些地区建造桥梁和管道。 此外，辫状河冲积层是水、油、气、煤、砂、砾石和重矿物的重要储集层。 它们的不稳定性和随机流动模式使得辫状河的预测极其困难。最近的进展提出了一些新的方法来分析这些复杂的动力系统。 现在很清楚，辫状河表现出空间和动态（时间-空间）缩放;即一小部分的河流网络是统计学上类似的一个更大的部分，在平面形状的几何形状和演变，在适当的resealing。 这一观测结果开辟了从容易获得的较低震级但更频繁的事件发生在较小尺度上的记录中统计预测罕见的高震级通道偏移的可能性。 同样清楚的是，至少有一些这些系统的缩放或“新兴”的属性的辫状河可以预测的基础上简化模型的流动力学。 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显着影响适度数量的银行植被;它甚至有可能转化为蜿蜒的河流植被的影响单独。我们建议联合和建立在这三个方面的研究，重点放在以下基本问题：（1）将辫状河标度分析扩展到第三维（垂向），流量、流速、河床高程和沉积物通量的比例，对现代河流洪水、冲刷和流动性的统计预测以及古代沉积物的地层结构具有意义;（2）利用水文比例结果作为模型度量标准，测试和改进现有的辫状河模型;（3）植被对辫状河的影响研究，重点关注水流和植被的重复循环如何导致辫状河流入少量明确定义的河道的“规则化”，打破了规模，也许导致了第一个真正自我再生的河曲的发展。

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.