Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2001
Publication Date: 8/20/2001
Citation: Pierson, Jr., F.B., Robichaud, P.R., Spaeth, K.E.,2001. Spatial and temporal effects of wildfire on the hydrology of a steep rangeland watershed. Hydrological Processes 15:2905-2916.
Interpretive Summary: Wildfire is a major management issue on western rangelands. The impacts of wildfire on runoff and erosion are not well understood. A study of the impact of wildfire on runoff was conducted on the 1999 34,400-ha Denio fire in northwestern Nevada. Runoff and erosion rates were measured immediately after, and one year following, the fire using simulated rainfall techniques. Impacts of the fire on runoff and erosion were directly compared to nearby unburned areas. Fire can cause the soil surface to become water repellent and thereby increase runoff and erosion rates. An index of water repellency was derived and used to quantify the influence of water-repellent soil conditions. Results showed that the impact of the fire was centered on areas directly under shrubs that have high accumulations of surface litter that can burn very hot. Areas under the shrubs also had nearly four times the amount of erosion compared to unburned areas. The impact of the fire on runoff and erosion was reduced, but still evident, one year after fire. These results will aid in management of future wildfires by helping land managers predict the risk of flooding and severe erosion following wildfire.
Technical Abstract: Wildfire is a major ecological process and management issue on western rangelands. The impacts of wildfire on hydrologic processes such as infiltration, runoff, and erosion are not well understood. Small-plot rainfall simulation methods were applied in a rangeland wildfire setting to determine post-fire hydrologic response. Infiltration and interrill erosion processes were measured immediately post-fire and one-year following the 1999 34,400-ha Denio fire in northwestern Nevada. Plot- scale spatial temporal variability in fire impacts was compared to adjacent unburned areas. An index of water repellency was derived and used to quantify the influence of water-repellent soil conditions on infiltration. Results indicate the impact of the fire on infiltration was localized primarily on coppice microsites directly under shrubs characterized by high surface litter accumulations. Coppice microsites had very uniform fire-induced soil water repellency with 29 of 30 plots exhibiting at least a 10 percent reduction in initial infiltration with an average 28 percent reduction. Cumulative erosion was nearly four times higher on burned coppices compared to unburned coppices. The impact of the fire on infiltration and erosion was reduced, but still evident, one year after fire.