As part of a Natural Resource Damage Assessment settlement related to contaminant releases from the Molycorp/Questa Molybdenum mine, subalpine fens, wetlands, and associated stream habitat for the native Rio Grande cutthroat trout are being restored in high-altitude headwaters of Bitter Creek, in the Midnight Meadows management area of Carson National Forest, New Mexico. Working with the U.S. Department of the Interior’s Office of Restoration and Damage Assessment, the U.S. Department of Agriculture, Forest Service, and the Amigos Bravos water conservation organization, USGS scientists collected imagery during September 2018 using unmanned aircraft systems (UAS, or “drones”) to document degraded upland and wetland vegetation and stream channel conditions during the early stages of restoration. The UAS missions demonstrated the utility of the UAS platform near its published air density altitude limits. Photogrammetric processing of images yielded a three-dimensional (3D) point cloud, a digital surface model, and an orthorectified, mosaicked image of the high-altitude fen complex. These products document current conditions and provide baseline data for monitoring 1) the restoration effectiveness of erosion control structures based on terrain changes, 2) hydrologic changes in the creek and contributing fens, and 3) changes in vegetation composition and structure. Ongoing collaboration is identifying additional ways in which UAS data can complement on-the-ground vegetation and habitat monitoring.
The digital surface model (upper left) and orthoimagery (lower left) for the Midnight Meadows restoration site can be used to measure head cuts such as that pictured at right. Repeated measures and plant special distribution mapping through time will allow assessment of erosion rates and changes in hydrology to determine if erosion control structures are having the desired effects.