failures are associated with roads that have drainage problems, or with streambanks that have been 

 undercut by stream flow. 



Wildfire Disturbances 



The historic fire regime for the Big Creek watershed is predominantly a Lethal T\re regime, with a 200+ 

 year return interval. The remainder of the basin has a Mixed fire regime, with a 80 to 120 year return 

 interval. Fires typically were large within the Big Creek watershed. A fire history analysis indicates that 

 this area typically burned with large wildfires that ran through the tree crowns and killed most of the 

 trees. There was 31% of the watershed burned in 1910, 6% in 1919, 5% in 1926, and less than 1 % 

 since fire suppression activities have been implemented (Moose Fire discussed below). Most likely 

 large fires burning significant portions of the basin represent the type of fire activity that has been 

 common in Big Creek since glacial times. 



It seems reasonable to assume that there were times following these fires when large acreages lacked 

 vegetative cover and the soils were exposed to the erosive forces of rains, wind, and snow melts. 

 However, there are few indicators that massive erosion occurred following these fires. When one looks 

 at the current landscape in the Big Creek area there is little evidence that this type of erosion scenarios 

 has occurred since the deposition of the volcanic ash layer (6-8 inches thick), from the eruption of Mt. 

 Mazama in southwest Oregon. If numerous significant erosion events had occurred since the volcanic 

 ash was deposited one would see areas that lack the ash surface or that have gullies. Instead, dry 

 ephemeral channels are blanketed by the ash material. Another feature that would indicate severe soil 

 erosion following fires or other natural disturbances would be the accumulation of eroded ash at the 

 base of steep slopes. This situation is not apparent. 



The amount of erosion that occurred after a wildfire could be deduced from observations following two 

 large wildfires that have occurred on the Flathead National Forest since 1994; the Little Wolf and the 

 Challenge fires on Tally Lake and Hungry Horst Ranger Districts respectively. Both of these fires 

 burned about 1 0,000 acres of fuel that were similar to those in the Big Creek watershed. Both of these 

 fires have had very little erosion. In most cases the fire left behind a changed layer of duff and litter that 

 protected the soil surface from erosion. 



Once a site has had the forest vegetation killed by wildfire there is a hydrologic response of increased 

 water yield from that site. It takes many years for the site to hydrologically recover; for the habitat types 

 that predominate in Big Creek the time frame for 100% hydrologic recovery can be in excess of 100 

 years. (WATSED 1995, Galbreath 1973). Therefore risk of stand replacement fire and its effects on 

 water yield increase must be considered during the development of the watershed restoration plan, as 

 well as other proposed vegetation manipulation activities in Big Creek. 



Effects of the Moose Fire August - November 2001 



On August 17, 2001 a wildfire started in the upper portion of the Big Creek watershed. By October 5* 

 the fire had burned over 71,000 acres on the Flathead National Forest, Coal Creek State Forest, and 

 Glacier National Park. Thirty-eight percent of the entire 52,000 acre Big Creek Watershed burned in 

 the Moose Fire. The majority of the fire was a stand replacement fire with moderate burn severity 

 (describes soil heating). The following disscussion described the existing post-fire situation for the 

 burned lands in Big Creek. Refer to Figure - 9, page 39 for a map showing the Big Creek Basin and 

 the portion of the Moose Fire on forest service lands. 



Soil Erosion - Soils under pre-fire conditions, generally supported an organic duff layer. The surface 

 layer of organic duff ranges from 1 to 4 inches in depth. The upper soil contains typically contains a 



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