Morphodynamic response of alluvial rivers to changes in flow

在加拿大各地，人们越来越关注河流水流状况变化的影响和水资源的安全。河流对流量的变化非常敏感。与气候变化相关的降水模式的预期变化将导致河流和溪流中更强烈和更频繁的洪水事件。在短期和长期内发生更剧烈变化的可能性对河流的完整性构成严重威胁，损害了河流满足经济、社会和生态功能的能力。这些极端事件可以显著改变河流的形态动力学（流沙相互作用）过程。从实际的角度来看，能够量化和预测这些变化是很重要的，因为它们涉及大量的侵蚀和沉积，可以破坏水力结构，侵蚀土地，并对水生生态系统产生负面影响。在城市环境中，预测形态动力学响应的能力变得越来越重要，因为城市环境对河流的需求越来越大，泛滥平原受到侵蚀，极端事件造成的经济损失风险也越来越大。由于其复杂性和动态性，河流的形态动力学调整对临时流量增加的响应难以准确预测和评估。考虑到这一点，本研究的目标是更好地理解冲积曲流对与极端事件相关的流量变化的性质和时间形态动力学响应。为了实现这一目标，本研究将结合实验室和数值工具来评估流量增加对曲流中沉积物和侵蚀过程的影响。实验室实验将揭示河床和河岸的形态调整与暂时的流量增加有关，包括渐进和快速变化的影响。将测量河流形态、输沙率和水流结构的时间演变。除了形态调整外，还将研究非均匀沉积物床（更能代表自然界条件）对流量增加的性质和反应。数值模拟将使用获得的实验室数据来模拟与连续极端降水事件相关的长期河流形态变化，并将为河流工程师和管理者创造一个预测工具。*这项研究的贡献将为气候变化对河流形态动力学的预期影响提供更多的知识。这将为未来河流和溪流周围的土地利用和开发提供更准确的指导，并改进侵蚀和沉积保护措施的设计，以确保水工结构和河流工程基础设施的安全。研究结果对河流工程师和水文学家也具有实际意义，有助于更好地了解河流的自然行为，从而改善河流的恢复、修复和再自然化工作，并为数值建模者提供更多的细节。这项研究将培养能够在一个充满活力和多学科领域工作的水环境工程师。这项工作的结果和实际应用将导致对河流和溪流进行更明智的管理，从而确保加拿大水资源的可持续管理。

Across Canada there is growing concern regarding the effect of changes to flow regime in rivers and the security of water resources. Rivers are very sensitive to alterations in flow. The anticipated changes in precipitation patterns associated with climate change will result in more intense and frequent flooding events in rivers and streams. The potential for more drastic changes over both the short- and long-terms pose serious threats to the integrity of rivers, compromising their ability to satisfy economic, social and ecological functions. These extreme events can significantly alter the morphodynamic (interaction between flow and sediment) processes in rivers. From a practical standpoint, it is important to be able to quantify and predict these changes as they involve substantial erosion and sedimentation which can damage hydraulic structures, erode land, and negatively impact aquatic ecosystems. The ability to predict morphodynamic response becomes increasingly important in urban environments where there are increasing demands on rivers, encroachment into the floodplain, and greater risk of economic loss resulting from extreme events. Due to their complex and dynamic nature, river morphodynamic adjustments in response to temporary increases in flow prove difficult to accurately predict and assess. * Considering this, the goal of this research is to develop a greater understanding of the nature and temporal morphodynamic response of alluvial meandering streams to changes in flow associated with extreme events. To accomplish this goal, this research will apply a combination of laboratory and numerical tools to evaluate alterations to sediment and erosion processes in meandering streams resulting from increases in flow. Laboratory experiments will reveal the morphological adjustments of the stream bed and banks associated with temporary increases in flow, including the effect of gradual and rapid changes. The temporal evolution of the stream morphology, sediment transport rates and flow structure will be measured. In addition to morphological adjustments, the nature and response of non-uniform sediment beds (more representative of conditions in nature) to increases in flow will also be examined. Numerical modeling will use the acquired laboratory data to simulate the long-term stream morphological changes associated with successive extreme precipitation events and will create a predictive tool for river engineers and managers. * The contributions made by this research will provide greater knowledge on the anticipated effects of climate change on stream morphodynamics. This will enable more accurate guidelines for future land-use and development around rivers and streams, and improved design of erosion and sedimentation protection measures to ensure the security of hydraulic structures and river engineering infrastructure. Results will also be of practical importance to river engineers and hydrologists, providing greater understanding of natural river behaviour for improved stream restoration, rehabilitation and re-naturalization efforts, and an increased level of detail for numerical modelers. This research will result in the training of hydro-environmental engineers, capable of working in a dynamic and multi-disciplinary field. Results and practical applications of this work will lead to more informed management of rivers and streams, thus ensuring sustainable management of Canada's water resources.