many fine plant roots, and many small pores and stabile soil aggregates, that in combination facilitated 

 rapid water infiltration and percolation. The pre-fire surface erosion rates were very low to non-existent 

 in undisturbed portions of the watershed. 



A wildfire has the potential to impact the soil beyond the limits of natural variability, including reduced 

 soil aggregate stability, reduced permeability, increased runoff and erosion, and reduced organic 

 matter/nutrient status. These combined effects will cause the runoff following a rain event to increase 

 significantly, increasing the overland flow available to initiate soil erosion, either as sheet or rill erosion. 

 The potential for erosion is highest on the steeper slopes that burned with a high burn severity. Burn 

 severity describes the effects of the fire on the soil hydrologic function (amount of surface litter, 

 erodibility, infiltration rate, runoff response) and productivity. Generally there is a close correlation 

 between these soil properties and the amount of heat experienced by the soil as well as the residence 

 time of the heat in contact with the soil. 



The low burn severity sites will naturally re-vegetate rapidly and have no/very low potential for soil 

 erosion. The Moose Creek fire had several large areas of moderate burn severity with inclusions of 

 smaller areas of high burn severity within these large burned patches. Most of the moderate and high 

 burn severity occurred on shrub dominated sites, which typically have good natural re-vegetation 

 potential following wildfire. The moderate burn severity sites are expected to re-vegetate rapidly. 

 However, the high burn severity sites initially have will be less vegetation re-growth (vegetation cover) 

 to protect the surface soil from erosion, especially when compared to the low burn severity areas. 



The post-fire aerial observations and follow-up ground investigations revealed that vast majority of the 

 moderate burn severity on the Flathead NF did not have very much potential to deliver sediment into a 

 stream channel. The primarily reasons for that interpretation is the expected natural re-vegetation 

 response, and the general lack of expected soil erosion. The assumption of low rates of expected soil 

 erosion is based upon the fact that the post-fire hydrophobic soil condition tends to ameliorate itself with 

 2 to 3 weeks with low intensity rain events which slowly wets the surface soil layers. Under normal 

 precipitation events we would not expect to see any severe soil erosion from the vast majority of hill- 

 slopes in the burn area. We would expect the post-fire responses in most watersheds that had a 

 significant percentage of their area in moderate or high burn severity to be the following: (1) an initial 

 flush of ash into the creeks; (2) to some extent rill and some small gully erosion in the ephemeral 

 drainages on the steep valley walls with the high burn severity. However if intense rainstorm were to 

 occur over the fire area some significant erosion could be expected from some of the moderate bum 

 severity and the high burn severity sites. The potential soil erosion modeling shows that more than 30 

 tons per acre of soil loss could occur with an intense rainstorm before all the post-fire hydrophobic soil 

 conditions recover and the sites are revegetated. 



The only area of significant upland soil erosion potential Is a high burn severity area, located in steep to 

 very steep hill-slopes (50-70% slope) in the SE1/4 of Section 34, the SW1/4 of Section 35, and NW1/4 

 of Section 3, of what is being called Skookoleel Creek North. This site has the potential for significant 

 surface soil erosion to occur and for the eroded material to be delivered directly to creek, which would 

 then be transported as sediment into the spawning gravel area in Big Creek, near the Skookoleel 

 Bridge. During the Burned Area Emergency Rehabilitation (BAER) efforts there were several erosion 

 reduction practices implemented in the Skookoleel Creek North area. 



None of identified mass failure sites or the unstable stream reaches in lower Big Creek should have any 

 significant increase in potential sediment yield due to the wildfire. These sources are basically 

 unchanged from the fire, but they still need the restoration work planned prior to the fire. The only 

 change from the fire was the loss of some riparian shrub plantings (2000 and 2001) along the 

 streambanks of lower Big Creek that may need to be replaced. 



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