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Environmental and Engineering Geoscience

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Development of a Soil Conservation Standard and Guidelines for OHV Recreation Management in California

¹ California Geological Survey, 801 K St., Suite 1324, Sacramento, CA 95814

View larger version (59K): [in this window] [in a new window]   Figure 1. Map showing general locations of 270 OHV areas in California. Nine of these areas (shown with star) are state-owned and/or state-managed SVRAs. The remaining OHV areas are predominantly owned and operated by BLM or USFS. The soil conservation standard and guidelines apply to all SVRAs and all federal and local projects that receive state-funded OHV grants. (Graphics by Lisa Ohara)

View larger version (100K): [in this window] [in a new window]   Figure 2. The recent closure of many OHV trails in California's desert lands has resulted in increased usage in areas that have remained open, especially those in close proximity to large metropolitan areas. OHV areas such as Heber Dunes SVRA, Ocotillo Wells SVRA, and Imperial Sand Dunes east of San Diego may experience anywhere between 15,000 to 200,000 OHV users a day during peak-season weekends. (Photo by Kelley Ristau)

View larger version (127K): [in this window] [in a new window]   Figure 3. Since implementation of California's 1991 Guidelines/Standard, new OHV equipment, like the high-powered dune buggies pictured here, have become popular with many recreational OHV riders. (Photo by Kelley Ristau)

View larger version (95K): [in this window] [in a new window]   Figure 4. These mesquite sand dunes at Ocotillo Wells SVRA offer enhanced all-terrain vehicle riding opportunities while protecting the 70–100 year old shrubs. The use of designated trails is required in the unfenced mesquite area to the right of the photo, while a portion of the dunes to the left of the photo is fenced to allow restoration. Springs seep from the ground year-round, providing an oasis for wildlife, including birds, lizards, and coyotes. Archeological investigations have indicated that several Native American groups and early settlers used the now-protected site for shade, water, and trading practices. (Photo by Kelley Ristau)

View larger version (49K): [in this window] [in a new window]   Figure 5. Map of California showing locations of the three OHV pilot study areas and other OHV areas where site visits were made during development of the updated standard/guidelines. Hollister Hills SVRA is underlain primarily by Tertiary-age fine-grained sandstone, siltstone, and shale in fault contact with older granite and schist typical of the Coast Ranges. The Foresthill OHV area is composed of a variety of Sierra Nevada rock formations, including Tertiary volcanics, metamorphosed sedimentary rocks, serpentinite, and other ultramafic rocks. The Dove Springs OHV Area is underlain predominantly by erodible Quaternary alluvial fan deposits, tuffs, and volcanic mudflows in a semi-arid desert environment. Other sites visited by CGS included a diverse set of ecosystems with multiple soil and vegetation types representative of the state's complex topographic, geologic, and climatic framework. (Graphics by Mel Patel)

View larger version (144K): [in this window] [in a new window]   Figure 6. OHV trails along the ridge top have diverted water from its natural watershed on the far side of the ridge onto trails leading into the hill climb in the foreground of the photo, thereby accelerating erosion on the hill climb slope. Proper installation and redirection of drainage along ridge top trails will hydrologically disconnect the two watersheds and reduce erosion and sedimentation in this area. (Photo courtesy of CSP)

View larger version (175K): [in this window] [in a new window]   Figure 7. Active headcuts and culvert blockage often occur at watercourse crossings where low-gradient roads and trails are maintained on steeper-gradient slopes. Insufficient and misplaced drainage along the all-terrain vehicle trail, combined with insufficient culvert-sizing and maintenance, has resulted in both partial blockage of the culvert and continued erosion of soils near the culvert outlet. (Photo by Stephen Reynolds)

View larger version (149K): [in this window] [in a new window]   Figure 8. Areas with a large number of "volunteer" trails may indicate the need for planned trails of higher difficulty in order to control erosion and sediment delivery, as well as satisfy the rider community with higher skill levels. Determining the general recreational profile of the people who use an OHV facility on a regular basis (i.e., through user surveys) can help in the planning of soil projects that will reduce the development of unauthorized trail systems. (Photo by Stephen Reynolds)

View larger version (121K): [in this window] [in a new window]   Figure 9. Erosion and sediment impacts are high along multiple-use roads (i.e., those used for access to activities other than OHV riding; left and center), in the vicinity of staging areas and campsites (right background), and in highly erodible soils regardless of slope steepness and overland water flow (foreground). Such impacts can be reduced by surfacing multiple-use roads and parking/staging areas with crushed rock, limiting campsites to managed areas, and designing drainage to avoid concentrated water flow. (Photo by Stephen Reynolds)