Soil Ecology Restoration Group

last update April 24, 1997

HUNGRY VALLEY - restoration

Hungry Valley State Park is an off-highway vehicle recreation area located in the mountains north of Los Angeles where the western edge of the Mojave ecosystem intersects with the coastal mountain range. The area has a long history of grazing, agriculture, and more recently, off-highway vehicle operation and pipeline construction. Progressive erosion, most dramatically on the hill climbs used by off-highway vehicles, has had an increasing impact on the native communities and on the capabilities of the park to function as an off-highway recreation area. SERG has been contracted to develop erosion control strategies that will allow continued use with minimal erosion or cyclic use with periodic rest and rehabilitation of the high use areas.

The primary focus of the work at Hungry Valley is on the restoration of the soils that have been impacted by the long history of disturbance in the area. These impacts to the soil include physical, chemical and biological factors such as: reduced infiltration and fertility, increased compaction and soil strength, reduced biological activity and resultant decrease in the aboveground biomass. These factors lead to a change in how water flows through the system, causing increased runoff, peak flow and erosion potential. Retention of the rainfall is the first step in mitigating the impacts of years of disturbance since the change that has occurred from perennial shrub/grassland to degraded annual weedland causing a ten-fold increase in runoff.

Several methods to increase water retention are being used at Hungry Valley. Contour ripping is being conducted on the more severely compacted soils. Pitting is also being done in various areas, both by machine in large areas and by hand in smaller hard to reach areas. These pits will not only catch and hold rainfall but serve as catchments for seeds and organic matter and thus aid in the reestablishment of ground cover. Imprinting, a similar method to pitting but normally providing smaller depressions in the soil, is also being tested on several sites. Various mulches such as bark, rice straw and rice hulls are also being tested to aid in the increase of soil microorganisms such as bacteria and fungi that are required to reestablish a self-sustaining mineralization process necessary for perennial plant growth.

Stabilization of current erosion gullies is of major concern and several methods are being used at Hungry Valley. Bamboo and coir check dams are being used for small gullies with moderate to low slopes. For wide gullies, straw bale check dams are being established. The use of T posts and wire mesh/brush check dams are being tested on higher gradient gullies. By establishing these check dams and backfilling before the rains arrive, these gullies can be brought back to the level of the surrounding area. Native vegetation will then be reestablished through broadcast seeding and seedling transplants to provide long-term stabilization of the slopes. Once slopes have been stabilized, a rotational use program will be established to prevent the reoccurrence of serious erosion impacts and allow time for rehabilitation.

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