Hydraulic Mining Sediments in the Bear and South Yuba Rivers of California

在世界许多地方，人类对自然环境的一种重要影响形式是使用水力采矿技术造成的破坏。这些技术使用加压水来松动和运输大量的覆盖层和矿石，将大量的沉积物和废水引入自然流域。美国最早大规模使用水力采矿发生在19世纪50年代至80年代的加利福尼亚北部的金矿。在本世纪初的几十年里，包括吉尔伯特（G.K. Gilbert）在内的科学家把相当多的注意力集中在人为引起的地貌变化过程上，但最近几十年，自然地理学家、地质学家、水文学家和其他学者把注意力转向了沉积过程的其他方面。该项目将建立在早期对加利福尼亚北部水力采矿影响的研究和最近对与人类有关的沉积活动的研究基础上，以检查贝尔河和南尤巴河上游沉积物的重新分配。该项目将由四个相互关联的部分组成：(1)将利用航空照片、卫星图像和实地调查期间采集的样品绘制过去和现在采矿沉积物的位置和体积；(2)将测量沉积物的持续流动性；(3)将确定1986年创纪录的洪水造成的河道和沉积物分布的变化；(4)测量采矿与非采矿沉积物的混合程度。这项研究将有许多理论和实践上的好处。它将首次对吉尔伯特在20世纪10年代首次提出的泥沙运移模型进行长期重新评估，使用其他学者可以使用的测量和分析技术。虽然侧重于采矿活动产生的沉积物，但该项目将对河流内所有类型沉积物的移动速度和体积提供更准确的估计。这种更好的理解将为更有效地制定有关停止和清理全国河流加速沉积的决策提供基础。

In many parts of the world, a significant form of human impact on the natural environment has been the disruption caused by using hydraulic mining techniques. These techniques, which use pressurized water to loosen and transport enormous amounts of overburden and ore, introduced enormous quantities of sediment and waste water into natural watersheds. The earliest large-scale use of hydraulic mining in the United States took place in the gold fields of northern California between the 1850s and the 1880s. Considerable attention was focused on the processes of human-induced geomorphic change by scientists including G.K. Gilbert in the early decades of this century, but physical geographers, geologists, hydrologists, and other scholars have turned their attention toward other facets of sedimentary processes in more recent decades. This project will build upon earlier studies of the impacts of hydraulic mining in northern California and more recent work on human-related sedimentary activity to examine the ongoing redistribution of sediment in the upper stretches of the Bear and South Yuba rivers. The project will consist of four interrelated parts: (1) past and present locations and volumes of mining sediments will be mapped using aerial photographs, satellite images, and samples taken during field surveys, (2) measurements of sustained sediment mobility will be made, (3) the changes in stream channels and sediment distributions resulting from a record flood in 1986 will be determined, and (4) the extent of mixing between mining and non-mining sediments will be measured. This research will have a number of theoretical and practical benefits. It will provide the first long-term reassessment of a model of sediment transport first developed by Gilbert in the 1910s, using measurement and analytic techniques that can be used by scholars elsewhere. Although focusing on sediments resulting from mining activities, the project will provide more accurate estimates of the rate and volume of movement for all types of sediments within streams. This improved understanding will provide a basis for more effective decision making regarding the cessation and clean-up of accelerated sedimentation in the nation's streams.