River dynamics and resilience of fluvial systems in perturbed environments

由于人类的影响和全球环境的变化，河流系统承受着相当大的压力。人们日益认识到，河流管理办法必须摆脱使河流保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，结合了更多的自然过程，如曲流动力学和洪泛平原的连通性，应该会产生更有弹性的系统，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在各种环境扰动下，河流的自由空间可能会或可能不会改变河流系统的长期状况。具体研究的环境扰动包括：与基础设施保护相关的河岸稳定，农业河流的河流矫直和疏浚，以及导致支流流域更频繁的山洪暴发的气候变化导致的河流横向流动性降低。长期目标将通过数值模拟和现场实验的结合和相互作用来实现。短期目标是：1)开发工具来描述更容易受到流量变化影响的河段特征，以便估计在哪里最有效地为河流系统中的自然河流过程提供更多空间；2)在魁北克省的农业流域中，研究将水文地貌学概念纳入溪流矫正和疏浚管理方法的适用性；3)评估小支流流域山洪增加对汇流带和主河道流动性的影响。本研究计划的科学方法是基于对受人为干扰影响的几条河流的实地数据收集。现场测量包括详细的河床地形、地表和地下粒度、河床输运、流速、浊度、阶段和流量。现场部分结合地理信息系统（GIS）分析和数值模拟实验。我的研究实验室最近开发了水文地貌学GIS工具，利用高分辨率激光雷达数字高程模型（dem）的可用性，将进一步开发，以帮助描述特定流域的主要分支和支流通道的水流功率和脆弱性，以应对未来气候中预期的流量变异性增加。该项目将在建立基于水文地貌学概念的河流管理专业知识方面取得重大进展，以解决一系列河流的主要环境问题，并在开发地理信息系统和建模工具方面取得重大进展，以便更好地向河流管理者通报气候变化背景下易受影响的河流。

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.