Measuring geomorphic processes at the watershed-scale to support urban river management

城区河流洪涝加剧，侵蚀迅速，水质不佳，生态健康恶化。在城市发展所需的洪水和侵蚀控制与河流的物理和生态完整性之间取得平衡仍然是一项重大的管理挑战，防止和恢复城市河流退化的努力在全球范围内是一个数十亿美元的产业。然而，当前城市河流管理战略所依赖的科学和工具仍然不足以支持管理目标，城市河流退化现象依然存在。地貌学是研究河流的物理形态及其随时间变化的学科，越来越多地被认为是支撑其他河流过程的基础，如水生生境可用性、营养物质和污染物转移以及洪水水力学。尽管城市河流地貌很重要，但由于缺乏城市地区的数据和研究，我们对城市河流地貌的理解仍然存在很大差距。在进行地貌学研究的地方，由于收集地貌数据的难度和成本较高，通常仅限于几百米的相对较小的研究区域。然而，地貌过程的空间有限的快照无法将它们与在分水岭尺度上运行的更大规模的压力源联系起来，例如土地利用的变化。这项研究计划旨在利用新兴技术和分析技术，通过研究比以前更大规模的地貌过程，扩大我们对城市化如何导致河流退化的理解。未来5年的目标是：1)确定可以探测流域内对城市化敏感的区域的地貌指标；2)测量泥沙如何通过城市流域获得、储存和转移，以及这与河流退化有何联系；3)建立针对城市流域的地貌方程和模型。这些目标将通过在汉密尔顿、多伦多和基奇纳-滑铁卢市区的研究地点进行详细的测量、泥沙输送监测和地貌建模来实现。该计划将利用无人机和激光雷达测量等新技术、创新的沉积物跟踪技术和先进的计算机模型来实现这些目标。目前城市河道修复管理的做法比较陈旧，缺乏科学严谨性，导致城市河道治理工程故障率高，维护成本高。这项研究的长期目标是开发新的工具，以支持环境顾问、河流修复工程师和流域管理人员围绕城市河流做出更多基于科学的决策。这些进展将有助于改善加拿大和全球城市河流的健康和完整性，从而降低洪灾和减缓侵蚀的成本，并在日益城市化的世界保护我们的自然环境。

Rivers in urban areas experience increased flooding, rapid erosion, poor water quality, and the deterioration of ecological health. Balancing the flood and erosion control that urban development requires with the physical and ecological integrity of rivers remains a significant management challenge, and efforts to prevent and restore urban river degradation accounts for a multi-billion-dollar industry globally. However, the science and tools upon which current urban river management strategies rely on remain inadequate to support management goals, and urban river degradation persists. Geomorphology, the study the physical form of rivers and its changes over time, is increasingly recognized as the foundation that underpins other river processes such as aquatic habitat availability, nutrient and contaminant transfer, and flood hydraulics. Despite its importance, our understanding of urban river geomorphology continues to have significant gaps due to a lack of data and studies in urban areas. Where geomorphology studies take place, they are typically limited to relatively small study areas of several hundred of meters due to the difficulty and high-cost of gathering geomorphic data. However, spatially-limited snapshots of geomorphic processes fail to connect them to the larger-scale stressors operating at the watershed scale, such as land-use change. This research program aims to use emerging technology and analysis techniques to expand our understanding of how urbanization leads to river degradation by studying geomorphic processes at larger scales than previously done. Objectives over the next 5 years are to 1) identify geomorphic indicators that can detect areas within a watershed that are sensitive to urbanization, 2) measure how sediment is sourced, stored, and transferred through urban watersheds and how this links to river degradation, and 3) build geomorphic equations and models specific to urban watersheds. The objectives will be met by conducting detailed surveying, sediment transport monitoring, and geomorphic modelling in study sites located in the Hamilton, Toronto, and Kitchener-Waterloo urban areas. The program will take advantage of new technology such as drone and lidar surveying, innovative sediment tracking technology, and advanced computer models to reach these objectives. The current practice of urban river restoration and management is outdated and lacking scientific rigour, which leads to the high failure rates and maintenance costs of urban river management projects. The long-term goal of this research is the development of new tools to support environmental consultants, river restoration engineers, and watershed managers in making more science-based decisions around urban rivers. These advancements will help improve the health and integrity of urban rivers in Canada and globally, leading to reduced flooding and erosion mitigation costs as well as the protection of our natural environment in an increasingly urban world.