Mountain stream adjustments to changes in flow and sediment supply regimes

山区的大规模运动经常将泥沙直接输送到河流网络，导致耦合条件，在相对较大的输送事件中可以立即触发河道反应。值得注意的是，递送事件可以重置本地渠道配置文件，并管理递送点下游的渠道床架构的构建和维护。输沙事件后的当地响应率和轨迹是普遍的分水岭水流状况、事件规模、河道宽度的梯度以及在某些情况下鲑鱼等水生物种的活动密度的函数。虽然低地河流系统一直是大量研究的重点，但在山区河流中开展的工作要少得多，关于山区河道对水流或泥沙供应制度变化的反应的工作也很少。 我的研究计划的目标是帮助建立一个更完整的山地河流系统知识库，我的主要兴趣是研究这些系统如何对径流和泥沙供应的变化做出反应。径流和泥沙供应的变化或两者的变化在物理上表现为对当地推移质泥沙输移速率和幅度的响应。因此，我的工作的中心重点是泥沙输运，最终，我希望发展在广泛条件下的河道响应轨迹的预测能力，纳入对泥沙输运和河道属性(形态、纹理、结构)的充分物理描述。预测能力可作为自然资源管理者的基本工具，在河流生态系统因气候和土地利用变化而面临日益频繁和/或极端的景观干扰时是迫切需要的。 展望我未来五年的研究计划，在上述背景下，我建议进行水槽试验和数值模拟，以：(1)描述单个颗粒的携带、移动距离和休止期；(2)分析池式冲刷形态的发展和维持，以响应水流和泥沙供应(结构和数量)的变化；(3)研究水文形状和输沙方式对泥沙输移和床面演变的影响。在CFI资助的山区航道水力实验实验室进行的实验详细描述了在现场环境中难以获得的物理过程，并使用数值模拟来进一步探索河流系统在可能的控制区域内的响应。拟议的项目将大大加深我们对山区溪流河道稳定性的了解，这是许多方面的关键问题--理论、管理、恢复、保护--也是河流地貌学的一个新兴前沿课题。

Mass movements in mountainous regions often deliver sediment directly to the stream network, resulting in coupled conditions that can trigger immediate channel responses during relatively large delivery events. Notably, delivery events can reset the local channel profile and govern construction and maintenance of channel-bed architecture downstream of delivery points. The local response rate and trajectory following a sediment delivery event is a function of the prevailing watershed flow regime, the event magnitude, gradients in channel width, and in some instances the activity concentration of aquatic species such as salmon. Whereas lowland river systems have been the focus of a substantial body of research, much less work has been carried out within mountain streams and little concerning mountain channel responses to changes in flow or sediment supply regimes. The objective of my research program is to help build a more complete knowledge base of mountain stream systems, and my principle interest is to examine how these systems respond to changes in streamflow and sediment supply. Changes in either or both streamflow and sediment supply physically manifests itself as a response in local rates and magnitudes of bedload sediment transport. As a result, the central emphasis of my work is sediment transport and, ultimately, I would like to develop predictive capabilities of channel response trajectories under a broad range of conditions, incorporating adequate physical descriptions of sediment transport and channel properties (morphology, texture, structure). Predictive capabilities can serve as a basic tool for natural resource managers and are urgently needed as stream ecosystems face increasingly frequent and/or extreme landscape disturbances due to climate and land use changes. Looking forward to the next five years of my research program, and within the context described above, I propose to conduct flume experiments and numerical simulations to: (1) describe particle entrainment, travel distance and rest period of individual grains, (2) analyze the development and maintenance of pool-riffle morphologies in response to changes in flow regime and sediment supply (texture and amount), and (3) to study the impact of hydrograph shape and sediment feed regime on sediment transport and bed surface evolution. Experiments conducted in the CFI-funded Mountain Channel Hydraulic Experimental Laboratory provide detailed descriptions of physical processes that are difficult to obtain in a field setting, and numerical simulations are used to further explore responses of the fluvial system across plausible control regimes. The proposed project will substantially develop our understanding of channel stability in mountain streams, which is a critical issue on many fronts - theoretical, management, restoration, conservation - and an emerging frontier topic in fluvial geomorphology.