The effects of selected postfire emergency rehabilitation techniques on small watershed sediment yields in southern California

Abstract

Forest Service Research has quantified the effects of selected Burned Area Emergency Response (BAER)treatments on sediment yields from small watershed by constructing dams to impound runoff and measuredebris from several burn sites in southern California. In this paper, we cite examples from three studies todemonstrate the effectiveness of these treatments. In 1999 the Mixing Fire burned over 1200 hectares ofmixed pine/oak forest with a brush understory on granitic terrain in the San Bernardino National Forest.A 1-hectare watershed treated with log erosion barriers (LEBs) was compared to a nearby untreated burnedcatchment. Results indicate that, although the LEBs retained considerable sediment, unforeseen differencesin site characteristics masked any differences in treatment effectiveness. The 2002 Williams Fire burned over15,000 hectares of chaparral on largely metamorphic terrain on the Angeles National Forest. Seven different1- to 2-hectare watersheds were used to compare the effects of the soil flocculent polyacrylamide (PAM)or prefabricated small-diameter log structures as channel check dams against nearby untreated watersheds.Results indicate that PAM had no effect but that the channel check dams significantly reduced sedimentyield. In 2003, the Cedar Fire burned about 117,000 hectares of brush on granitic terrain in the ClevelandNational Forest. Three 2- to 3-hectare watersheds were used to compare two levels of an aerial hydromulchtreatment (100 percent treated and 50 percent contour strips) to a nearby untreated watershed. Preliminaryresults indicate that the 50 percent treatment produced more sediment than the untreated but the 100percent treatment generated less than half the sediment of the untreated watershed. Rigorous testing needs tocontinue before these erosion control treatments become standard practice.

Parent Publication

• Advancing the fundamental sciences: proceedings of the Forest Service National Earth Sciences Conference, San Diego, CA, 18-22 October 2004.

Citation

Wohlgemuth, Peter M.; Robichaud, Peter R. 2007. The effects of selected postfire emergency rehabilitation techniques on small watershed sediment yields in southern California. In: Furniss, M.; Clifton, C.; Ronnenberg, K., eds. 2007. Advancing the fundamental sciences: proceedings of the Forest Service National Earth Sciences Conference. Gen. Tech. Rep. PNW-GTR-689. Portland, OR: U.S. Forest Service, Pacific Northwest Research Station: 36-42.