New concepts for Meadow restoration in the northern Sierra Nevada

摘要

The Feather River Coordinated Resource Management (FRCRM) group, a partnership of 21 public and private sector watershed stakeholders, has over a decade of experience in designing and implementing watershed restoration projects in California's upper Feather River basin. Due to historical land abuse, 98 percent of the meadows in the watershed are degraded and require man's intervention to reverse current trends. Accelerated erosion, gully formation, lack of desirable riparian vegetation, habitat loss, and flashy runoff patterns are consequences of a watershed that has lost hydrologic and biologic function. The FRCRM identified degraded meadows as a high priority for restoration and several new innovative approaches to meadow restoration have been designed and tested with successful results. The Big Flat Meadow Project is an example. The Big Flat Meadow/Cottonwood Creek Restoration Project, located in the Plumas National Forest, was initiated in 1994 by the FRCRM to restore hydrologic function to meadow resources. Historically, Cottonwood Creek maintained groundwater levels in the Big Flat Meadow that supported mesic vegetation; however, intense grazing, logging, and road building over the preceding 90 years resulted in relocation of Cottonwood Creek and the creation of a gully 10-15 feet deep. As the new channel eroded and incised, subsurface meadow aquifers drained, vegetation converted from wet meadow species to xeric species, and the pattern of surface flow was modified from perennial to intermittent. Loss of meadow function lead to a dramatic change in hydrology, diminishing subsurface water storage and flood attenuation capacity. From a list of potential alternatives, the FRCRM selected a unique "pond and plug" restoration approach to enhance the hydrology and ecology of Big Flat Meadow. This unique geomorphic approach was the first-in-kind demonstration in California. The strategy involved moving the stream to its historic location, reconstruction of the historic channel, and filling in the existing gully with soil excavated from onsite ponds created to enhance waterfowl habitat. Preliminary results indicate that the successful reconnection of the channel to its naturally evolved floodplain has extended the period of stream flow, moderated the magnitude and duration of peak flow events, and reduced seasonal ground water fluctuation indicating increased ground water storage. Meadow vegetation is more productive and has shifted to wetter site species. The modified grazing system has encouraged vegetation establishment and minimized mechanical streambank damage along the new channel. Continued monitoring will determine whether the modified hydrologic regime will lead to long term changes in meadow vegetation, water storage capacity and the social benefits due to extended late season flow.