Abrasion by Bedload and Suspended Load: Experimental Study

摘要：亚利桑那州立大学水槽研究？推移质和悬移质冲刷：实验研究？切入岩石的河流在从实际到学术的各种问题中都扮演着重要的角色。从大坝溢洪道设计，到河流管理规划，包括维护山区河流合适的水生栖息地和河流恢复工作，再到对山区河流的坡度、宽度和粗糙度的长期控制，对河流切入岩石的力学进行定量了解是至关重要的，也是人们广泛关注的问题。在过去的十年里，在理解气候、地形、侵蚀和构造之间的相互作用方面取得了实质性的进展；认识到河流切割岩石的核心作用是一项关键的洞察。然而，对基岩河道作用的探索主要是通过简化的水流动力模型(河流切割的通用规则集，将各种侵蚀机制集合在一起)来完成的。精确的、更现实的模型预测需要在我们对侵蚀过程的定量理解方面取得进展。基岩切割过程的现场调查是必要的，但不能让研究人员完全控制关键变量。越来越多的受控实验室实验被用来探索河流切割物理的基本方面，测试现有的模型，并指导它们的改进。亚利桑那州立大学的这项研究项目包括水槽实验、数据分析和理论发展。这些实验将被设计来补充和扩展以前的水槽研究。主要控制变量(泥沙通量和粒度分布；河道坡度；排水量和底质硬度)将在系统的条件探索中有所不同，包括从推移质到悬移质的过渡。将允许河床形态自然演变，并将量化河床形态、流体动力学、泥沙通量和局部侵蚀速率之间的关键反馈。基于初步实验、野外观测和以前的数值研究，我们制定了定量假设，这些假设可以并将通过直接测量侵蚀速率、河床地形、颗粒跃迁轨迹、泥沙输送速率和流体流动条件进行检验，从而使当前的理论得以完善。这一研究项目的结果将对基础科学和一些与社会相关的实际问题产生重要影响。了解基岩岩性、沉积物特征和河道形态之间关系的进展，对于解决尽量减少和减轻土地利用影响以及恢复受损的河流生境和生态系统等应用问题具有潜在的重要价值。工程规划和管理要求了解控制河道变化的过程，包括河床粗糙度和冲积盖层特征。一名博士后研究员、一名研究生和几名本科生将从这个研究项目中获得宝贵的培训。此外，还将开发用于本科生课程和公共宣传活动的实验室演示。

Abstract: ASU Flume Study ?Abrasion by Bedload and Suspended Load: Experimental Study?River incision into rock plays an important role in diverse problems ranging from practical to academic. From dam spillway design, to river management planning including maintenance of suitable aquatic habitats in mountain rivers and river restoration efforts, to the long-term controls on the slope, width, and roughness of mountain rivers, a quantitative understanding of the mechanics of river incision into rock is essential and of broad interest. There has been substantial progress in the past decade on understanding the interactions among climate, topography, erosion, and tectonics; recognition of the central role of river incision into rock has been a key insight. Exploration of the role played by bedrock channels, however, has been accomplished primarily with simplified stream power models (generic rule sets for river incision that lump together a diverse set of erosional mechanisms). Refined, and more realistic, model predictions require advances in our quantitative understanding of erosion processes. Field-based investigation of bedrock incision processes is essential, but does not allow the investigator full control of critical variables. Controlled laboratory experiments have increasingly been used to explore fundamental aspects of the physics of river incision, to test existing models, and to guide their refinement. This research project at ASU includes flume experiments, data analysis, and theoretical development. The experiments will be designed to complement and extend previous flume studies. The primary controlling variables (flux and size distribution of sediment; channel slope; water discharge; and substrate hardness) will be varied in a systematic exploration of conditions, including the transition from bedload to suspended load transport. Bed morphology will be allowed to evolve naturally, and the critical feedbacks between bed morphology, fluid dynamics, sediment flux, and local erosion rate will be quantified. Based on preliminary experiments, field observations, and previous numerical studies, we formulate quantitative hypotheses that can and will be tested by direct measurement of erosion rate, bed topography, grain saltation trajectories, sediment transport rate, and fluid flow conditions, thus allowing refinement of current theory. The results from this research project will have important implications for basic science and a number of practical concerns of societal relevance. Advances in the understanding of the linkages between bedrock lithology, sediment characteristics and channel morphology are of potentially great value in solving applied problems of minimizing and mitigating for landuse impacts and restoring damaged riverine habitat and ecosystems. Engineering planning and management demand understanding of the processes that govern channel changes, including bed roughness and alluvial cover characteristics. A postdoctoral researcher, a graduate student and several undergraduates will receive invaluable training from this research project. Also, laboratory demonstrations will be developed for use in undergraduate courses and for public outreach events.