Meadow Restoration Monitoring with American Rivers
In July 2022, ForeSight Drone Services partnered with American Rivers to provide aerial mapping of three meadows in the Eldorado National Forest of California’s Sierra Nevada. American Rivers (AR) is a national nonprofit that has been engaged in protecting wild rivers, restoring damaged rivers and conserving clean water for people and nature since 1973. AR’s California Headwaters Restoration Program focuses on source water restoration and protection, which largely includes meadow restoration in the Sierra Nevada. The Sierra Nevada provides water to more than 75% of Californians and healthy meadows play an integral part in this; providing surface flows, groundwater storage, and water quality benefits.
Healthy meadows provide a suite of benefits including improved groundwater storage, enhanced water quality, reduced peak flood flows, critical habitat, and resilience to climate change. It’s estimated that 50% of Sierra meadows are degraded by human impacts, resulting in the loss of these benefits. AR is working to restore two degraded meadows, Calf Pasture and Wilson Ranch, in the South Fork American watershed. The overall goal of this Project is to return natural hydrology. Specifically, the Project will use nearby soils to fill in erosion features, which will reactivate historical meadow channels and improve the stream’s connection with its floodplain. This will allow water to soak into the groundwater table and result in the suite of benefits described previously.
On Thursday, July 12, 2022 ForeSight’s Elias Grant, along with Maiya Greenwood, AR’s Associate Director of California Conservation, spent 11 hours in the Eldorado National Forest 4 miles west of Desolation Wilderness mapping Calf Pasture, Wilson Ranch, and Van Vleck Meadows. Elias used a DJI Mavic 2 Pro paired with the Pix4D Mapping App to capture over 600 images of Calf Pasture, Wilson Ranch, and Van Vleck meadows. For post processing, Agisoft Metashape was used to stitch orthomosaics and DEM’s.
Aerial imagery of the two degraded meadow systems (Wilson Ranch and Calf Pasture), and one reference meadow (Van Vleck) was used to create a map quantifying how much area is supporting wetland vegetation and where the wetland plant communities are located. The information from this vegetation mapping was used to document pre-restoration conditions and provide a healthy reference site (Van Vleck) for comparison. AR hired botanists to look at the orthomosaics and classify areas into detailed plant communities based on color (greenness), % cover, and geomorphology. Following this, the botanists conducted field surveys to identify individual species in each community.
Field mapping of vegetation types by the wetland indicator status of the dominant plant species provided a way to quantify how much of the vegetation at the two restoration meadows is currently supported by local hydrology and functioning as a wet meadow. At the healthy Van Vleck meadow, over 70% of the area is dominated by hydrophytic species. At the unhealthy Calf Pasture and Wilson Ranch meadow systems, wetland (or hydrophytic) plants dominated less than eight percent of the area mapped. Transects and plots were established in all three sites and selected to represent current geomorphic features and the mosaic of vegetation they support. The transects and plots in Wilson Ranch and Calf Pasture were located to capture changes resulting from restoration.
Post-restoration aerial data will be collected several years after restoration and used to create another vegetation map, which will provide a comparison of how dominant plant species changed over space and time. The goal is to see more obligate and facultative wetland species following post-restoration data collection and analysis. This mapping will enable AR to quantify the benefits and effectiveness of the restoration activities, and clearly communicate the impact to all stakeholders.