Collaborative Research: Role of lithologic variability in controlling downstream channel response to sediment pulses

山区的山体滑坡会产生大量的碎片，这些碎片被河流侵蚀，流向下游人口稠密的低地地区。这些滑坡的砾石大小的成分可以积聚在河床上，增加下游社区洪水的频率。由此产生的河床岩石大小的变化可以改变生活在那里的鱼类和昆虫的栖息地。另外，如果滑坡中的沉积物比沙子还小，就会导致浑浊的水，需要昂贵的过滤才能饮用或灌溉，而且往往对生活在河里的鱼、昆虫和其他动物有害。不同的河流和滑坡泥沙特征对下游的影响是重要的，因为气候变化可能会增加滑坡和受影响河流内移动的泥沙量。该项目将确定沉积物的岩石类型（密度和耐久性）在多大程度上控制沉积物积聚的时间和规模以及河床的大小组成，特别关注太平洋西北部火山地形中的那些河流。该项目将通过短期的夜间实地考察，向新的学生介绍地球科学，参与研究，并与地区洪水管理者分享结果。在太平洋西北地区，在火山地形上发生了不成比例的重大物质消耗事件，产生了密度和磨损率不等的沉积物脉冲。该项目将使用实地观测和建模来描述河道对这些大沉积物脉冲的敏感性。研究的重点是沉积物脉冲的岩性特征如何控制下游河道响应的时间和幅度。解决这个问题的方法是：量化几个盆地中块体沉积特征的变异性；在对下游磨损和河道响应有良好场约束的情况下，对河流中特定质量损耗事件的下游命运进行建模；并利用该模型确定河流系统对泥沙脉冲和河道特征观测范围的敏感性，该模型基于对具有独特特征（如磨损率和密度）的单个泥沙“包”的拉格朗日跟踪。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Landslides in mountainous regions produce large volumes of debris that are eroded by rivers and travel downstream to populated lowland areas. The gravel-size components of these landslides can accumulate on the streambed and increase the frequency of flooding in downstream communities. The resultant changes in the rock sizes in the riverbed can alter habitat for fish and insects that live there. Alternatively, if the sediment in the landslide is smaller than sand, it can result in cloudier water that requires costly filtration for drinking water or irrigation and is often harmful to the fish, insects, and other animals living in the river. The downstream effects of different river and landslide sediment characteristics are important as climate change threatens to increase landslides and the amount of sediment moving within affected rivers. This project will determine the degree to which the rock type (density and durability) of the sediment controls the timing and magnitude of sediment accumulation and size composition on the riverbed, with specific attention to those rivers in the volcanic terrain of the Pacific Northwest. The project will introduce new students to the Earth Sciences through short overnight field excursions to participate in the research and share results with regional flood managers.In the Pacific Northwest, a disproportionate number of major mass-wasting events occur in volcanic terrain, producing sediment pulses of variable density and abrasion rate. This project will use field observations and modeling to characterize river channel sensitivity to these large sediment pulses. The research focuses on how the lithologic characteristics of sediment pulses control the timing and magnitude of downstream channel response. This question will be addressed by: quantifying the variability in the sedimentary characteristics of mass-wasting deposits in several basins; modeling the downstream fate of a specific mass-wasting event in a river for which there are good field constraints on downstream abrasion and channel response; and determining the sensitivity of the river system to observed ranges of sediment pulse and channel characteristics using the model, which is based on Lagrangian tracking of individual sediment “parcels” that have unique characteristics such as abrasion rate and density.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.