Successful management of flooding and erosion hazards on floodplains depends on our ability to predict a river channel's shape and the lifespan during which it will continue to flow. Recent progress has improved our understanding of what sets the lifespan and width of single-thread channels; the next challenge is to extend this knowledge to braided channels and their interwoven sub-channels (threads). In this study, we investigate the lifespan and width of braided channel threads in a large experimental data set, coupled with particle-image velocimetry-derived measurements of riverbank erosion and accretion. We find that, unlike single-thread channels, braided channels in the experiment do not exhibit an equilibrium between bank erosion and accretion. Instead, bank erosion outpaces lateral accretion, causing individual threads to widen and infill until they are abandoned. Thread lifespan is limited to the time it takes for threads to triple their width: tripling of the width yields enough bank material to aggrade more than half the channel depth, at which point flow is rerouted to a narrower thread. In consequence the width of active threads is limited to three times their initial width. Threshold channel theory accurately predicts the median thread width, which is roughly double the initial width and two-thirds the limiting width. The results are consistent with existing field data and suggest that differential bank migration is sufficient to explain why braided channels show greater width variability and higher width-to-depth ratios than their single-thread counterparts.

中文翻译：

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差分银行迁移限制了编织通道螺纹的寿命和宽度

洪泛区洪水和侵蚀危害的成功管理取决于我们预测河道形状及其持续流动的寿命的能力。最近的进展提高了我们对什么决定了单线程通道的寿命和宽度的理解；下一个挑战是将这些知识扩展到编织通道及其交织的子通道（线程）。在这项研究中，我们研究了大型实验数据集中编织通道线的寿命和宽度，并结合粒子图像测速法得出的河岸侵蚀和吸积测量结果。我们发现，与单线通道不同，实验中的编织通道在堤岸侵蚀和吸积之间没有表现出平衡。相反，河岸侵蚀超过横向吸积，导致单个线程变宽并填充，直到它们被废弃。螺纹的使用寿命仅限于螺纹宽度增加三倍所需的时间：宽度增加三倍会产生足够的堤岸材料来聚集超过一半的通道深度，此时流量会重新路由到更窄的螺纹。因此，活动螺纹的宽度被限制为它们初始宽度的三倍。阈值通道理论准确地预测了中线宽度，大约是初始宽度的两倍和极限宽度的三分之二。结果与现有的现场数据一致，并表明不同的堤岸迁移足以解释为什么编织通道显示出比其单线程对应物更大的宽度变化和更高的宽深比。螺纹的使用寿命仅限于螺纹宽度增加三倍所需的时间：宽度增加三倍会产生足够的堤岸材料来聚集超过一半的通道深度，此时流量会重新路由到更窄的螺纹。因此，活动螺纹的宽度被限制为它们初始宽度的三倍。阈值通道理论准确地预测了中线宽度，大约是初始宽度的两倍和极限宽度的三分之二。结果与现有的现场数据一致，并表明差异岸迁移足以解释为什么编织通道显示出比单线程对应物更大的宽度变化和更高的宽深比。螺纹的使用寿命仅限于螺纹宽度增加三倍所需的时间：宽度增加三倍会产生足够的堤岸材料来聚集超过一半的通道深度，此时流量会重新路由到更窄的螺纹。因此，活动螺纹的宽度被限制为它们初始宽度的三倍。阈值通道理论准确地预测了中线宽度，大约是初始宽度的两倍和极限宽度的三分之二。结果与现有的现场数据一致，并表明不同的堤岸迁移足以解释为什么编织通道显示出比其单线程对应物更大的宽度变化和更高的宽深比。此时流量被重新路由到更窄的线程。因此，活动螺纹的宽度被限制为它们初始宽度的三倍。阈值通道理论准确地预测了中线宽度，大约是初始宽度的两倍和极限宽度的三分之二。结果与现有的现场数据一致，并表明差异岸迁移足以解释为什么编织通道显示出比单线程对应物更大的宽度变化和更高的宽深比。此时流量被重新路由到更窄的线程。因此，活动螺纹的宽度被限制为它们初始宽度的三倍。阈值通道理论准确地预测了中线宽度，大约是初始宽度的两倍和极限宽度的三分之二。结果与现有的现场数据一致，并表明不同的堤岸迁移足以解释为什么编织通道显示出比其单线程对应物更大的宽度变化和更高的宽深比。