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

在加州内华达山脉的水力采矿取代了大量的沉积物，作为从砂石中提取黄金的副产品。近百年来，美国加州萨克拉门托河谷下游汛期水工泥沙改造与沉积的空间分布关系到该流域的污染物命运、洪水输送和土地利用，同时也关系到流域底泥收支和洪泛平原沉积的基础研究。本研究采用了一套新的技术和数据来调查上个世纪中央山谷洪泛区沉积和塞拉山前水力采矿沉积物侵蚀之间的时空联系。最近的现场证据表明，间歇性的山前侵蚀和绕道沉积要求对上个世纪萨克拉门托下游山谷的水力采矿沉积物输送问题进行新的调查。这项研究将追踪萨克拉门托河谷下游水力采矿尾矿产生的细沉积物的运动。研究小组将把萨特和约洛绕道（中央山谷的堤岸洪泛平原）的时空格局和沉积过程与最后一个主要水坝下游的贝尔河、尤巴河和羽毛河的山前尾矿的侵蚀联系起来。它将通过结合摄影测量、河道变化分析和实地调查，追踪山前水力采矿沉积物的历史侵蚀情况。该小组将通过粒度测定法、x射线荧光光谱法、磁学和地质年代学来记录中央山谷采矿沉积物的历史和来源。此外，将仔细研究一个流量测量站网的记录，以便对山前侵蚀和中央河谷沉积之间的时间相关性进行确证分析。该项目将对沿山前通道的体积沉积物储存和侵蚀及其撤离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种来源的相对影响。它将确定旁路系统中离散沉积物的空间范围和体积，并记录跨越萨特和约洛旁路的各种横断面的沉积速率和历史。这项研究将根据历史水文学和旁路沉积过程的精细化概念模型，发展山前侵蚀和旁路沉积之间的定量联系。它将为未来洪水对通过中央山谷的沉积物运动的影响的预测建模提供基础。该项目将为萨克拉门托河谷今后的管理决策和方向提供数量基础，并提供一套可应用于其他大型管理河流流域的方法。本研究的数据和解释将对萨克拉门托下游山谷和三角洲的河流和环境管理具有重要的实际用途，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，包括那些历史上代表性不足的群体。这项研究的成果将通过万维网作为一个项目网站提供，并通过美国宇航局空间联盟（一个教育资源中心）直接向K-12提供科学服务。

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.