Assessment of Soil and Moisture Conservation Crew meadow restoration

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We investigated the historical use and long-term efficacy of hand-built check dams to repair eroded meadows of Sequoia and Kings Canyon National Parks (SEKI) to inform the design for restoring a large erosion gully in Cahoon Meadow, SEKI. Archive documents show that, for 34 years from 1948 to 1981, a summer-seasonal team of SEKI employees, the Soil and Moisture Conservation Crew (S&MCC), built and maintained check dams in 20 back country meadows and 1 front country meadow, and their erosion control efforts were requested, but never implemented, at an additional 33 meadows. S&MCC activities were focused on mitigating the impacts of grazing that occurred from ~1870 to 1985. The two meadows with the longest grazing history, Williams and Sugarloaf, were consistently rated as high priorities for erosion-control and received the most S&MCC check dam work. In 2015 we conducted field investigations in these two meadows, relocating as many dams as possible to determine how effective they were at accumulating sediment after 30 years of maintenance followed by 35 years with no work. We found 41 S&MCC check dams, 35 in Sugarloaf and 6 in Williams, and measured their channel dimensions, slope, sediment accumulation, and functionality. All but 2 of the dams were non-functional, retaining no water, and even dams in small, shallow sloping channels had failed. The maximum sediment accumulation depth was 1.2 meters, just upstream of a dam built in 1948, in a gully that had been 2.5 meters deep. On average, the sediment depth accumulated behind dams was 26% of the former gully depth. Nowhere did enough sediment accumulate behind a dam to fill in the local gully and restore the original level topography of the meadow. Although 30+ years of dam building and maintenance succeeded in locally depositing sediment to about a quarter of the eroded gully depth, the gully in Cahoon Meadow is deeper and wider than any of the dammed sections of either Williams or Sugarloaf Meadows. Wider, taller structures would be required in Cahoon’s gully and these would be significantly more difficult to design, build, and maintain than the S&MCC dams and require 100 years or more to accumulate enough sediment to completely restore original topography.
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