Collaborative Research: Tracking Hydraulic Mining Sediments from the Sierra Piedmont into Flood Bypasses of the Sacramento Valley, California

加利福尼亚州内华达山脉的水力采矿将大量的沉积物作为从砂砾中提取黄金的副产品。上个世纪水力开采泥沙改造和绕洪淤积的空间分布关系到污染物的去向、洪水的传输和加州萨克拉门托河谷下游的土地利用，该河谷正在进行大规模的恢复和开发计划，并与谷底泥沙收支和泛滥平原沉积的基础研究有关。这项研究采用了一套新的技术和数据，研究了上个世纪山前山脉中央河谷泛滥平原沉积和水力采矿沉积物侵蚀之间的时空联系。最近的山前侵蚀和绕过沉积的现场证据要求对上个世纪以来萨克拉门托河谷下游的水力采矿泥沙输送问题进行新的调查。这项研究将跟踪来自萨克拉门托河谷下游水力采矿尾矿的细颗粒沉积物的移动。研究小组将把萨特和约洛旁路(中央山谷的漫滩)的沉积时空模式和过程与各自最后一个主要大坝下游的下熊河、尤巴河和羽毛河的山前尾矿的侵蚀联系起来。它将通过摄影测量、河道变化分析和实地调查相结合，追踪山前水力采矿沉积物的历史侵蚀。该团队将通过粒度测量、X射线荧光光谱、磁学和地质年代学来记录中央山谷开采沉积物的历史和来源。此外，将仔细研究河流流量测量站网络的记录，以佐证分析山前侵蚀和中央山谷沉积之间的时间相关性。该项目将对皮埃蒙特海峡沿线的泥沙储量和侵蚀以及疏散时间进行定量的实地估计。它将记录采矿和非采矿沉积物的地球化学、粒度和磁性，并开发适当的混合模型，以识别通过河流系统下游的每个来源的相对影响。它将确定旁路系统中离散沉积物的空间范围和体积，并记录跨越Sutter和Yolo旁路的不同横断面的沉积速率和历史。这项研究将建立山前侵蚀和绕道沉积之间的定量联系，这些联系基于历史水文学和绕道沉积过程的精炼概念模型。该项目将为预测未来洪水对中央河谷泥沙运动的影响提供基础。该项目将为萨克拉门托河谷未来的管理决策和方向提供量化基础，并提供一套可应用于其他大型受管理河流流域的方法。这项研究的数据和解释将对萨克拉门托河谷下游和三角洲的河流和环境管理有很大的实用价值，我们的结果对洪水输送、岛屿维护和沉积物的潜在毒性至关重要。这项研究将为新一代地貌学家创造教育机会，包括那些来自历史上代表性不足的群体的人。这项研究的成果将通过万维网作为项目网站提供，并通过教育工作者资源中心NASA空间联盟提供直接的K-12科学宣传。

Hydraulic mining in the Sierra Nevada of California displaced great volumes of sediment as a byproduct of gold extraction from placer gravels. The spatial distribution of hydraulic mining sediment reworking and deposition in flood bypasses over the last century are relevant to the fate of contaminants, flood conveyance, and the land-use in the lower Sacramento Valley of California, which is undergoing a massive program of restoration and development, and to basic research on valley floor sediment budgets and floodplain sedimentation. This research employs a suite of new techniques and data to investigate the temporal and spatial links between Central Valley floodplain sedimentation and erosion of hydraulic mining sediment in the Sierra piedmont over the last century. Recent field evidence of episodic piedmont erosion and bypass deposition calls for a new investigation of the hydraulic mining sediment delivery problem in the lower Sacramento valley over the last century. The research will track the movement of fine sediments derived from hydraulic mining tailings in the lower Sacramento Valley. The research team will link spatial and temporal patterns and processes of deposition in Sutter and Yolo Bypasses (leveed floodplains of the Central Valley) with erosion of piedmont tailings of the lower Bear, Yuba, and Feather Rivers downstream of the last major dam on each. It will track historical erosion of hydraulic mining sediments in the piedmont through a combination of photogrammetry, channel change analysis, and field surveys. The team will document history and provenance of mining sediment deposits in the Central Valley by granulometry, X-ray fluorescence spectroscopy, magnetism, and geochronology. In addition, records from a network of streamflow gauging stations will be perused for corroborative analysis of temporal correlation between piedmont erosion and Central Valley sedimentation. The project will produce quantitative, field-based estimates of volumetric sediment storage and erosion along piedmont channels and the timing of its evacuation. It will document geochemical, grain size, and magnetic properties of mining and non-mining sediment and develop appropriate mixing models for discerning the relative influence of each source downstream through the fluvial system. It will identify the spatial extent and volume of discrete sediment deposits in the bypass system, and document sedimentation rates and histories along various transects spanning Sutter and Yolo Bypasses. The research will develop quantitative links between piedmont erosion and bypass deposition that are based on historical hydrology and refined conceptual models of bypass sedimentation processes. It will provide the basis for predictive modeling of the impact of future floods on sediment movement through the Central Valley.The project will provide a quantitative basis for future management decisions and direction in the Sacramento Valley and a set of methodologies that can be applied to other large, managed river basins. Data and interpretations from this study will be of great practical use to river and environmental management in the lower Sacramento Valley and the Delta, where our results are of utmost importance to flood conveyance, maintenance of islands, and potential toxicity of sediment. This research will create educational opportunities for a new generation of geomorphologists, including those from historically underrepresented groups. The output from this research will be made available as a project website via the World Wide Web and provide direct K-12 scientific outreach through the NASA space consortium, an educator resource center.