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ARS Home » Pacific West Area » Boise, Idaho » Northwest Watershed Research Center » Research » Publications at this Location » Publication #125732
Title: FIRE EFFECTS ON SEDIMENT AND RUNOFF IN STEEP RANGELAND WATERSHEDS

Author
item Pierson Jr, Frederick
item CARLSON, D - UNIVERSITY OF IDAHO
item SPAETH, K - NRCS

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/9/2001
Publication Date: 3/20/2001
Citation: Pierson, Jr., Frederick, B., Carlson, D.H., Spaeth, K.E., 2001, Fire effects on sediment and runoff in steep rangeland watersheds, Proceedings of the 7th Federal Interagency Sediment Conference (3-27-3-29-2001), Reno, NV., p. x23 - x40.

Interpretive Summary: Wildfires is a major management issue in western range and forest ecosystems. In forested ecosystems, research has shown that fire removes vegetation, surface litter and roots that protec the soil from erosion. Fires can also cause water repellent soil conditions which increases surface runoff and soil erosion. Little is known about the impact of wildfire and prescribed fire for fuels management on rangeland vegetation and soil conditions or how such interactions may affect hydrologic processes including infiltration, surface runoff, erosion, sediment production and transport, and flooding. Improved small-plot rainfall simulation techniques were used in wildland fire settings in Idaho and Nevada to determine post-fire hydrologic response. Results indicate significant fire effects on runoff and erosion response due exist from relatively moderate thunderstorms and snowmelt/frozen soil runoff events. Significant water repellency was found after wildfire in areas with high surface organic biomass. Soils studied were found to be more vulnerable to rill erosion from overland flow than sheet erosion from rainfall impact.

Technical Abstract: Wildfires is a major management issue in western range and forest ecosystems. A wildfire in August 1996 burned 4,850-ha of rangeland immediately above Idaho's capitol city of Boise. Over $12 million were spent for emergency rehabilitation to protect Boise against post-fire threat of accelerated runoff, erosion and flooding, but yet the city still experienced a flood event in 1997. Major unknowns associated with wildfire and prescribed fire for fuels management are effects on vegetation and soil conditions affecting hydrologic processes including infiltration, surface runoff, erosion, sediment production and transport, and flooding. Improved small-plot rainfall simulation techniques are being applied in wildland fire settings to determine post-fire hydrologic response. Runoff, erosion, sediment production, and longer-term basin hydrologic processes are analyzed from the Boise Fire and from the 1999 34,400-ha Denio Fire in northwestern Nevada. Results indicate significant fire effects on runoff and erosion response from relatively moderate thunderstorms and snowmelt/frozen soil runoff events.