Effects of Fire on Soil Erosion

Fire can indirectly lead to soil erosion by removing protective surface covers and altering soil physical properties. The degree of erosion depends on several factors, including:

• soil texture- coarse textured soils erode more readily
• slope- the steeper the slope, the more likelihood of erosion
• vegetation- quick recovery of vegetation can slow erosion
• fire severity- more severe burns increase likelihood of erosion
• litter and duff- residual layers of litter and duff can buffer erosion
• precipitation- high rates of post-burn rainfall increase chances of erosion 

Unlike areas in the Western U.S., where the combination of impaired hydrology, steep topography, and slow vegetative growth make fire-induced soil erosion a serious issue, large soil losses following prescribed fire are uncommon in the southern U.S.  While research consistently indicates that fires do increase erosion rates, the actual rates of soil loss are generally lower than erosion caused by other common forest operations (road building, harvesting, thinning, mechanical site preparation; Yoho 1980).  For example, studies conducted throughout the Coastal Plain and Piedmont reported higher erosion rates from burned areas than nearby unburned areas (Table:Fire Effects on Erosion in the S.E.). However, only one site (North Carolina: Copley et al 1944) showed erosion greatly exceeded natural background levels for the duration of the study (or 1.8 inches per 1,000 years, the estimated erosion rate in central US before large-scale human intervention) (Ralston and Hatcher 1971).  Several additional studies have also reported minimal or no soil erosion following low intensity prescribed fires in the Piedmont and Coastal Plain (Goebel and others 1967, Brender and Cooper 1968, Cushwa and others 1971, Douglass and Van Lear 1983). 

Southern Appalachians, Swift et al. (1993) reported that soil erosion was spotty and related to points of local soil disturbance; no soil left their study sites. The Forest Service in its site-preparation burning program on the Sumter National Forest in the mountains of South Carolina uses summer burns in heavy fuels with little visible evidence of soil erosion on slopes of up to 45 percent (Van Lear and Danielovich 1988). By comparison, soil losses as high as 27.6 tons/acre/year have been reported following intense wildfires in ponderosa pine forests (Campbell et al. 1977). 

Despite the lack of evidence for large soil losses following fires in the South, land managers should still assess the susceptibility of their particular site to soil damage and erosion and follow guidelines for mitigating these potential effects.  Coarse-textured soils on steep slopes may be particularly susceptible to erosion, particularly following intense site preparation burns or wildfires. For more information on this topic, see:

• Management guidelines for reducing fire effects on soil and water, and
• Tools for predicting risk of soil erosion or soil damage following prescribed burns.