Negligible geomorphic change occurred in a 1.5-square-kilometer watershed in southern Oregon during the first 2 years following intense wildfire. Parts of this watershed had been partly cut within eight years prior to the fire or had been clear-cut immediately prior to the fire. Precipitation during the two-year study period was about normal (86 percent of normal in the first wet season and 143 percent in second season). There were only minor effects from the wildfire in terms of development of hydrophobic soil conditions, and infiltration rates remained very high in relation to rainfall intensities. Average hillslope lowering rates computed from two erosion plots, reconnaissance measurements of ravel rates, and photograph comparisons are less than 0.001 meters per year, below the detection limits of these measurement techniques. Channel incision rates into gravelly alluvium during the first wet season were less than 0.001 meters per year and may not be related to wildfire occurrence. The negligible geomorphic response to this dramatic destruction of vegetation suggests that the geomorphic role of wildfires in the Pacific Northwest is not necessarily of large scale or magnitude. High infiltration rates, absence of widespread soil hydrophobicity, and low rainfall intensities mitigate erosional tendencies.
Additional publication details
USGS Numbered Series
Geomorphic response to wildfire following timber harvest of a small watershed in southern Oregon
Water-Resources Investigations Report
U.S. Geological Survey Cascades Volcano Observatory