River dynamics and resilience of fluvial systems in perturbed environments

由于人类影响和全球环境变化，河流系统面临着相当大的压力。人们越来越认识到，河流管理方法必须摆脱将河流保持在固定位置的硬工程结构。相反，一种以河流自由空间为基础的方法，结合了更多的自然过程，如曲折动力学和泛滥平原的连通性，应该会导致更具弹性的系统，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改变河流系统的长期条件。具体考察的环境扰动包括与基础设施保护相关的大量河岸稳定、农业溪流中的河流矫直和疏浚以及气候变化导致支流流域更频繁的山洪暴发，从而降低了河流的横向流动性。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，确定更易受流量变化影响的河段的特征，以便估计在哪里最有效地为自然河流过程提供更多在河流系统中运行的空间；2)审查将水文地貌概念纳入魁北克农业流域中拉直和疏浚河流的管理方法的适用性；3)评估小支流流域山洪增加对汇合带和主河道流动性的影响。这项研究计划的科学方法是基于对几个受人类干扰影响的河流河段的实地数据的收集。现场测量包括详细的河床地形、表层和次表层颗粒大小、推移质输运、流速、浊度、水位和流量。现场部分与地理信息系统(GIS)分析和数值模拟实验相结合。我的研究实验室最近开发的水文地貌地理信息系统工具，利用更多可用的高分辨率LiDAR数字高程模型(DEM)，将进一步开发，以帮助确定特定流域的主要支流和支流河道的水流功率和对未来气候预期流量变化增加的脆弱性的特征。该方案将在建立基于水文地貌概念的河流管理专门知识以解决一系列河流的主要环境问题方面取得重大进展，并在开发地理信息系统和建模工具以更好地向河流管理者通报气候变化背景下脆弱的河流河段方面取得重大进展。

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.