River dynamics and resilience of fluvial systems in perturbed environments

由于人类的影响和全球环境变化，河流系统受到相当大的压力。人们日益认识到，河流管理办法必须摆脱将河流维持在固定位置的硬工程结构。相反，一种基于河流自由空间的方法，它整合了更多的自然过程，如河曲动力学和洪泛区连通性，应该导致更有弹性的系统，特别是在气候变化的背景下。该研究计划的长期目标是测试河流的自由空间如何在各种环境扰动下可能会或可能不会改变河流系统的长期状况。具体审查的环境扰动是河流的横向流动性减少，这是由于与保护基础设施有关的严重河岸稳定、河流拉直和农业河流疏浚以及气候变化导致支流流域更频繁的山洪暴发。长期目标将通过数值模拟和实地试验的结合和相互作用来实现。短期目标是：（1）开发工具，描述更易受流量变化影响的河流河段，以估计在何处最有效地为河流系统中的自然河流过程提供更多的空间;（2）研究在魁北克农业流域中纳入拉直和疏浚河流的水文地貌概念的管理方法的适用性;以及3）评估汇流区小支流流域山洪暴发增加对主河道流动性的作用。该研究项目的科学方法是基于在受人类扰动影响的几个河流河段收集的实地数据。现场测量包括详细的河床地形，表面和次表面粒度，推移质输运，流速，浊度，水位和流量。实地部分与地理信息系统分析和数值模拟实验相结合。水文地貌地理信息系统工具最近在我的研究实验室开发，利用高分辨率激光雷达数字高程模型（DEM）的可用性增加，将进一步发展，以帮助描述在特定流域的主要分支和支流渠道在流功率和脆弱性方面的预期增加在未来的气候排放变化。该计划将允许在建立基于水文地貌概念的河流管理专业知识方面取得重大进展，以解决一系列河流中的主要环境问题，并开发GIS和建模工具，以更好地告知河流管理人员气候变化背景下的脆弱河流河段。

River systems are under considerable pressure due to human impacts and global environmental changes. It is increasingly recognized that river management approaches must move away from hard-engineering structures that maintain rivers in a fixed position. Instead, an approach based on freedom space for rivers, which integrates more natural processes such as meander dynamics and floodplain connectivity, should lead to more resilient systems, particularly in a climate change context. The long-term objective of the research program is to test how freedom space for rivers may or may not modify the long-term condition of fluvial systems under various environmental perturbations. Environmental perturbations that are specifically examined are reduced lateral mobility of streams resulting from heavy bank stabilization associated with protection of infrastructure, river straightening and dredging in agricultural streams, and climate change resulting in more frequent flash floods in tributary watersheds. The long-term objective will be reached through the combination of and interactions between numerical modelling and field experimentation. The short-term objectives are to 1) develop tools to characterize river reaches that are more vulnerable to discharge variability in order to estimate where it is most effective to provide more space for natural river processes to operate in fluvial systems; 2) examine the applicability of management approaches which incorporate hydrogeomorphological concepts for straightened and dredged streams in agricultural watersheds in the Quebec context; and 3) assess the role of increased flash floods in small tributary watersheds on the confluence zone and on the mobility of the main channel. The scientific approach of this research program is based on the collection of field data at several river reaches that are affected by human perturbations. Field measurements include detailed bed topography, surface and sub-surface grain size, bedload transport, velocity, turbidity, stage and discharge. The field component is combined with Geographical Information System (GIS) analysis and numerical modelling experiments. Hydrogeomorphological GIS tools recently developed in my research laboratory, making use of the increased availability of fine-resolution LiDAR Digital Elevation Models (DEMs), will be further developed to help characterize both main branches and tributary channels in specific watersheds in terms of stream power and vulnerability to the anticipated increase in discharge variability in future climate. This program will allow significant progress in establishing an expertise in river management based on hydrogeomorphological concepts to tackle major environmental problems in a range of rivers, and on developing GIS and modelling tools to better inform river managers about vulnerable river reaches in a climate change context.