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ARS Home » Pacific West Area » Boise, Idaho » Northwest Watershed Research Center » Research » Publications at this Location » Publication #168173
Title: Impacts of fire on hydrology and erosion in steep mountain big sagebrush communities

Author
item Pierson Jr, Frederick
item ROBICHAUD, P - FOREST SERVICE
item SPAETH, K - NRCS
item Moffet, Corey

Submitted to: First Interagency Conference on Research in the Watersheds
Publication Type: Proceedings
Publication Acceptance Date: 10/1/2003
Publication Date: 10/1/2003
Citation: Pierson, Jr., F.B., Robichaud, P.R., Spaeth, K.E., and Moffet, C.A. 2003. Impacts of fire on hydrology and erosion in steep mountain big sagebrush communities. In: Proceedings of the First Interagency Conference on Research in the Watersheds., Benson, AZ, p. 625-630.

Interpretive Summary: Wildfire is a major ecological process and management issue on western rangelands. Major unknowns associated with wildfire are its affects on vegetation and soil conditions that influence hydrologic processes including infiltration, surface runoff, erosion, sediment transport, and flooding. The influence of fire on hydrology and erosion was studied at the watershed-scale in big sagebrush plant communities on steep slopes with sandy soils. Significant rill erosion was observed following both thunderstorm and rapid snowmelt events. Artificial rainfall and surface overland flow were used to examine how fire changes infiltration, interrill and rill erosion processes. Results indicate that fire severity and the development of water repellent soil conditions after fire play significant roles in determining infiltration and interrill erosion rates, particularly on areas directly under shrubs that have high accumulations of surface litter. Fire had the biggest affect on rill erosion by reducing ground cover. Ground cover such as litter and rocks slow the movement of water and spread it out as it moves across the soil surface. Land managers can use this information to better estimate the hydrologic effects of wildfire and better target mitigation treatments aimed at reducing both on- and off-site impacts of fire.

Technical Abstract: Wildfire is a major ecological process and management issue on western rangelands. Major unknowns associated with wildfire are its affects on vegetation and soil conditions that influence hydrologic processes including infiltration, surface runoff, erosion, sediment transport, and flooding. Post wildfire hydrologic response was studied at the watershed-scale in big sagebrush plant communities on steep slopes with coarse textured soils. Significant rill erosion was observed following both thunderstorm and rapid snowmelt events. Rainfall simulation and controlled overland flow techniques were used to study post-fire effects on infiltration, interrill and rill erosion processes on burned and adjacent unburned areas. Results indicate that fire severity and the development of hydrophobic soil conditions play significant roles in determining infiltration and interrill erosion rates, particularly on shrub coppice dunes characterized by high surface litter accumulations. Fire had the most dramatic and long-lasting affect on rill erosion processes by reducing ground cover needed to slow and spread water as it moves across the soil surface. Ongoing research efforts are aimed at characterizing the hydrologic impacts of prescribed fire used as a tool to manage vegetation and mitigate the impacts of catastrophic wildfire events.