This paper offers a mechanism for meandering in an otherwise braided river and then discusses its general implications for river processes and fluvial deposits. Braided rivers manage to meander without the paired point bars and single-thread channels that are instrumental in developing bends in other meandering rivers. The driving processes for meandering in these braided systems remain enigmatic. The unchannelized and prechannelized Missouri River is an example of a braided meandering river, and it provides an opportunity to gain insight into these processes. This study utilized historical maps, sequential air photos, and surficial geologic maps both to define the processes by which this braided river meanders, and to characterize the deposits produced by these processes. These data show that the Missouri River meanders by building point assemblages instead of point bars. Repeated accretion of midchannel and lateral bars to a common point on the bank forces development of a meander bend around a point assemblage comprising multiple amalgamated compound bars. This differs from single-thread systems, which expand and translate bends around a single compound point bar. Alternating development of point assemblages forces meandering over successions of meander bends. Braided meander loops grow by expansion and translation like single-thread rivers, but they also may contract to produce counterpoint assemblages. Contraction appears to be the more common means of loop abandonment compared to loop cutoff for the braided Missouri River. This differs from single-thread meandering rivers, where contraction is limited, and loop cutoff is consistently the dominant abandonment process. Deposits of the braided meandering Missouri River differ from deposits of single-thread rivers in the rarity of both meander scrolls and single-thread channel fills. Instead, point and counterpoint assemblages comprise fusiform bar elements bound by small filled remnants of anabranch channels. These assemblages are commonly bound by meander cutbank scars. Cutbank scars associated with contraction, however, tend to be composite rather than discrete erosional surfaces, and they do not tend to bind river-scale abandoned channel fills. The braided meandering Missouri River also differs from wandering rivers because wandering rivers meander by building compound bars instead of assemblages, are more gravelly, have less pervasive and much less mobile midchannel bars, and appear to reflect a transitional intermediate pattern instead of a stable hybrid pattern. Braiding and meandering both expend stream power, and both are mechanisms for achieving channel equilibrium. The Missouri River exhibits both of these processes in tandem; thus, meandering and braiding are not mutually exclusive processes. Braided meandering rivers like the Missouri River are less common than either straight-braided or single-thread-meandering rivers, but they are not unique. The long-held distinction of braided versus meandering patterns for rivers thus may be practical but is not definitive.

中文翻译：

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蜿蜒的辫状河的案例：酒吧组合作为沿着美国密苏里河蜿蜒曲折的机制

本文提供了一种在其他辫状河中蜿蜒的机制，然后讨论了其对河流过程和河流沉积物的一般意义。编织河流在没有成对的点杆和单线通道的情况下蜿蜒曲折，这些通道有助于在其他蜿蜒的河流中形成弯道。在这些编织系统中蜿蜒的驱动过程仍然是个谜。未渠道化和预渠道化的密苏里河是辫状曲流河的一个例子，它提供了深入了解这些过程的机会。这项研究利用历史地图、连续航空照片和地表地质图来定义这条辫状河蜿蜒的过程，并描述这些过程产生的沉积物。这些数据表明，密苏里河通过建立点组合而不是点酒吧来蜿蜒曲折。中间渠道和横向钢筋重复增加到岸上的一个公共点，迫使在一个点组合周围形成曲折弯曲，该点组合包括多个合并的复合钢筋。这与单线系统不同，单线系统围绕单个复合点杆扩展和平移弯曲。点组合的交替发展迫使在连续的曲折弯道上蜿蜒曲折。编织曲流循环像单线河流一样通过扩展和平移而增长，但它们也可能收缩以产生对位组合。与编织密苏里河的环路截断相比，收缩似乎是更常见的环路放弃方式。这与收缩有限的单线蜿蜒河流不同，和循环截止始终是主要的放弃过程。辫状曲流密苏里河的沉积物与单线河流的沉积物不同，在于曲流卷轴和单线河道填充物的稀有性。取而代之的是，点和对点组合由梭形条形元素组成，这些元素由小枝条通道的小填充残余物约束。这些组合通常受到蜿蜒的割缝疤痕的约束。然而，与收缩相关的切岸疤痕往往是复合的，而不是离散的侵蚀面，而且它们不会束缚河流规模的废弃河道填充物。辫状蜿蜒的密苏里河也不同于流浪的河流，因为流浪的河流通过建造复合坝而不是组合来蜿蜒曲折，更砾石，更不普遍，流动性更差的中河道，并且似乎反映了过渡的中间模式而不是稳定的混合模式。编织和蜿蜒都消耗流功率，两者都是实现通道平衡的机制。密苏里河同时展示了这两个过程；因此，曲折和编织并不是相互排斥的过程。像密苏里河这样的编织蜿蜒河流比直编织河流或单线蜿蜒河流少见，但它们并不是独一无二的。因此，长期以来一直存在的河流编织与蜿蜒模式的区别可能是实用的，但不是确定的。蜿蜒和编织不是相互排斥的过程。像密苏里河这样的编织蜿蜒河流比直编织河流或单线蜿蜒河流少见，但它们并不是独一无二的。因此，长期以来一直存在的河流编织与蜿蜒模式的区别可能是实用的，但不是确定的。蜿蜒和编织不是相互排斥的过程。像密苏里河这样的编织蜿蜒河流比直编织河流或单线蜿蜒河流少见，但它们并不是独一无二的。因此，长期以来一直存在的河流辫状与蜿蜒模式的区别可能是实用的，但不是确定的。