Study Area Boundary Malakoff DIggins State Historic Park, California

One of the largest hydraulic mines (1.6 km2) is located in California’s Sierra Nevada within the Humbug Creek watershed and Malakoff Diggins State Historic Park (MDSHP). MDSHP’s denuded and dissected landscape is composed of weathered Eocene auriferous sediments susceptible to chronic rill and gully erosion whereas block failures and debris flows occur in more cohesive terrain. This data release includes a 2014 digital elevation model (DEM), a study area boundary, and a geomorphic map. The 2014 DEM was derived from an available aerial LiDAR dataset collected in 2014 by the California Department of Conservation. The geomorphic map was derived for the study area from using a multi-scale spatial analysis. A topographic position index (TPI) was created using focal statistics to compare the elevations across the study area. We calculated a fine-scale TPI using a circular neighborhood with a radius of 25-meters and large-scale TPI using a circular neighborhood with a radius of 100-meters. In the resulting raster positive TPI values are assigned to cells with elevations higher than the surrounding area and negative TPI values are assigned to cells with elevations lower than the surrounding area. The geomorphic map was then created using a nested conditional statement to apply classification thresholds on the basis the fine and large-scale TPI rasters and a slope raster. Ten geomorphic feature classes were defined and the map can be symbolized by feature class. The geomorphic map includes both channel and hillslope features and can be used to assess erosional and depositional processes at the landscape scale.

作为全球规模较大的水力采矿场之一（占地面积1.6平方千米），该场地位于加利福尼亚州内华达山脉的洪堡溪流域范围内，隶属于马拉科夫迪金斯州立历史公园（Malakoff Diggins State Historic Park，简称MDSHP）。MDSHP园区内剥蚀切割形成的地貌由风化的始新世含金沉积物组成，此类沉积物极易发生长期细沟与沟壑侵蚀；而在黏性更强的地表区域，则易发生块体崩塌与碎屑流灾害。本次数据集发布包含2014年数字高程模型（DEM）、研究区边界矢量数据与地貌图。其中2014年DEM由加利福尼亚州保护部2014年采集的公开机载激光雷达（LiDAR）数据集生成。本次研究针对研究区开展多尺度空间分析以生成该地貌图：首先借助焦点统计工具计算地形位置指数（TPI），以对比研究区内的高程差异，分别采用半径25米的圆形邻域生成精细尺度TPI，采用半径100米的圆形邻域生成大尺度TPI。生成的栅格数据中，正TPI值对应高程高于周边区域的栅格单元，负TPI值则对应高程低于周边区域的栅格单元。随后通过嵌套条件语句，基于精细尺度与大尺度TPI栅格、坡度栅格设定分类阈值，最终完成地貌图的绘制。本次研究共定义了10类地貌要素类，可依据要素类对地貌图进行符号化渲染。该地貌图涵盖河道与山坡两类地貌特征，可用于评估景观尺度下的侵蚀与沉积过程。