Morphodynamic response of alluvial rivers to changes in flow

在整个加拿大，人们越来越关注河流流态变化和水资源安全的影响。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发生更强烈和更频繁的洪水事件。短期和长期可能发生更剧烈的变化，这对河流的完整性构成了严重威胁，损害了它们满足经济、社会和生态功能的能力。这些极端事件会显著改变河流的地貌动力学(水流和泥沙之间的相互作用)过程。从实际角度来看，重要的是能够量化和预测这些变化，因为它们涉及大量的侵蚀和沉积，可能破坏水工结构、侵蚀土地并对水生生态系统产生负面影响。在城市环境中，预测地形动态响应的能力变得越来越重要，因为城市环境对河流的需求不断增加，对泛滥平原的侵蚀，以及极端事件造成的经济损失风险更大。由于其复杂和动态的性质，河流地貌动态调整对临时流量增加的反应被证明很难准确地预测和评估。考虑到这一点，这项研究的目的是更好地了解冲积曲流河的性质和时间对与极端事件相关的水流变化的地貌动力学响应。为了实现这一目标，这项研究将应用实验室和数值工具相结合的方法来评估由于流量增加而导致的蜿蜒河流中泥沙和侵蚀过程的变化。实验室实验将揭示与流量暂时增加相关的河床和堤岸的形态调整，包括渐变和快速变化的影响。将测量河流形态、输沙速率和水流结构的时间演变。除了形态调整外，还将研究非均匀泥沙床(更能代表自然界的条件)的性质和对流量增加的反应。数值模拟将使用获得的实验室数据来模拟与连续的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人员创造一个预测工具。这项研究的贡献将为气候变化对河流地貌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方针，并改进侵蚀和泥沙保护措施的设计，以确保水工建筑物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，以改进河流恢复、恢复和重新归化的工作，并提高数值模拟人员的细节水平。这项研究将培养能够在动态和多学科领域工作的水环境工程师。这项工作的成果和实际应用将导致对河流和溪流进行更知情的管理，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.