When do boulders move in steep mountain streams?

陡峭的山涧里的巨石什么时候会移动？

• 批准号: 0922199
• 负责人: Michael Lamb
• 金额: $ 34.95万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0922199&HistoricalAwards=false
• 关键词: When; do; boulders; move; steep

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 11-5).Most of the rivers in hilly and mountainous landscapes have small, steep channels, which are typically mantled by boulders that rarely move. In these channels, boulders moderate the rate of river incision, roughen the flow creating local patches of gravel , and provide crucial habitat for a variety of organisms such as salmon and steelhead spawning. Coarse sediment can also become entrained by river floods, which rush down slope with considerable destructive consequences. No current theory or empirical model exists that successfully predicts the threshold of movement of boulders or their organization by river processes. This research project addresses this fundamental gap in basic knowledge through a combined theoretical, experimental and field-based approach. A semi-empirical theory for boulder mobility and step-pool formation will be developed and tested using a newly constructed state-of-the-art laboratory flume at the California Institute of Technology. The flume experiments will allow exploration of channel slopes (up to 30%) and grain sizes (up to 10 cm) that have been severely limited in past studies. Experiments will be designed to investigate the conditions under which boulders move and the mechanisms responsible for boulder organization into steps and pools. Data from these experiments will be used to test and validate predictive models for boulder transport and step-pool formation. The experimental and theoretical findings will be compared to observed flow conditions during boulder movement events in tributaries of the South Fork Eel River in the University of California Angelo Coast Range Reserve. The result will be a robust method for calculating boulder transport dynamics in steep mountain streams, with implications for predicting landscape evolution, the rate of movement of sediment through steep channels, critical habitat conditions, and the beneficial use of boulders in restoration projects. The results from this research project will have significant implications for basic science and a number of practical concerns of societal relevance. Results from this project will aid in restoration and hazard mitigation efforts where assessing boulder mobility is needed for restoring stream habitat (e.g., salmon spawning) and functionality, as well as mitigating flood and debris flow hazards in steep urban areas. This research project includes mentoring undergraduates, a PhD student, and a post-doctoral researcher in experimental, field and theoretical science. Research from this study will be uswd to design a 1-day workshop for area high-school teachers. The goal will be to give teachers the necessary skills to teach their students simple ways to assess flood and debris flow hazards that can result in loss of life and property in the Los Angeles area.

该奖项的资金来源是《2009 年美国复苏和再投资法案》（公法 11-5）。丘陵和山地地区的大多数河流都有小而陡的河道，这些河道通常覆盖着很少移动的巨石。 在这些河道中，巨石减缓了河流切割速度，使水流变得粗糙，形成了局部砾石斑块，并为鲑鱼和硬头鱼等产卵的各种生物提供了重要的栖息地。 河流洪水也会夹带粗沉积物，洪水冲下斜坡，造成相当大的破坏性后果。 目前还没有理论或经验模型能够成功预测巨石运动的阈值或其通过河流过程的组织。 该研究项目通过理论、实验和实地相结合的方法，解决了基础知识中的这一根本差距。 将使用加州理工学院新建的最先进的实验室水槽来开发和测试巨石流动性和阶梯池形成的半经验理论。水槽实验将允许探索过去研究中受到严重限制的河道坡度（高达 30%）和颗粒尺寸（高达 10 厘米）。 实验将被设计来研究巨石移动的条件以及巨石组织成台阶和水池的机制。 这些实验的数据将用于测试和验证巨石运输和阶梯池形成的预测模型。 实验和理论结果将与加州大学安杰洛海岸保护区南福克鳗河支流巨石运动事件期间观察到的水流条件进行比较。 其结果将是计算陡峭山间溪流中巨石运输动态的稳健方法，对预测景观演变、沉积物通过陡峭通道的移动速率、关键栖息地条件以及巨石在恢复项目中的有益利用具有重要意义。 该研究项目的结果将对基础科学和许多社会相关的实际问题产生重大影响。该项目的结果将有助于恢复和减灾工作，其中需要评估巨石的流动性，以恢复河流栖息地（例如鲑鱼产卵）和功能，以及减轻陡峭城市地区的洪水和泥石流灾害。 该研究项目包括指导实验、现场和理论科学领域的本科生、博士生和博士后研究员。这项研究的结果将用于为地区高中教师设计为期 1 天的研讨会。 目标是为教师提供必要的技能，教学生简单的方法来评估可能导致洛杉矶地区生命和财产损失的洪水和泥石流灾害。