A - Overview/Summary 



Big Creek is a major tributary (77 mile^^) to the North Fork Flathead River. The North Fork of the 

 Flathead River occupies portions of northwest Montana and southeast British Columbia, Canada. The 

 water yield in Big Creek is produced from an average annual precipitation in the basin that ranges from 

 62 inches at the top of Big Mountain to 28 inches along the North Fork Flathead River; approximately 

 60% of this precipitation falls as snow. Streamflows typically peak in late May or June as the snowpack 

 melts. The gradient of Big Creek tributaries in the uppermost portions of the watershed is approximately 

 1 ,000 feet per mile (18% stream slope). The gradient of the mainstem of Big Creek is 400 feet per mile 

 for the uppennost four miles (7% stream slope), 200 feet per mile for the stretch in which Big Creek 

 meanders on its valley floor (4% stream slope), and 70 feet per mile in the lowermost 8 miles near the 

 Big Creek Campground (1% stream slope). Big Creek is a key spawning stream for bull trout and 

 westslope cutthroat trout because of the clean water and its physical characteristics. 



The State of Montana has classified the waters in Big Creeks as B-1 , which is one of the highest 

 possible ratings. Waters classified as B-1 are suitable for drinking, culinary, and food processing 

 purposes after conventional treatment. Water quality must also be suitable for bathing, swimming, and 

 recreation; growth and propagation of salmonid fishes and associated aquatic life, waterfowl, and 

 furbearers; and agricultural and industrial water supply. 



There have been many management activities in the Big Creek basin in the past fifty years. These 

 include the construction of approximately 180 miles of roads. Also, vegetation management in one 

 form or another, either timber harvest or thinning, has occurred on approximately 16,691 acres of the 

 basin. (The vegetation management includes the clearing for portions of the Big Mountain Ski Area.) 

 The entire Big Creek basin is now currently owned and managed by the U. S. Forest Service. 



Field examination, qualitative, and quantitative stream monitoring confirm that the source of sediments 

 is from a combination of natural and man-caused upland and stream channel erosion. Big Creek is 

 formed in a glacial valley where natural streambank erosion rates are high. Historically, major 

 streambank erosion has occurred during extreme peak flow events, generally following past fires (1910 

 fire) and flood events (1964 flood). Currently there are several eroding stream terrace escarpments 

 that contribute sediment during high flow events. 



The past construction of roads and logging skid trail networks on both national forest and private lands 

 have caused an increased sediment load to Big Creek. At the same time, there was an increase in 

 water yield following the extensive timber harvest on Forest Service and private lands. This increased 

 water yield, in combination with the excess sediment supply, caused streambank instability and stream 

 channel erosion. This resulted in stream channel widening and stream pool filling from bedload 

 sediments that could not be transported by the stream. During the 1960s and 70s when management 

 activities were extensive, sediment supply exceeded transport capability in the upper basin of Big 

 Creek. Where the gradient of Big Creek is low, particularly in the stretches with less than 4% slope, 

 large quantities of sediments have been stored as point and mid-channel bars found upstream from 

 organic debris in the stream such as individual logs or log jams. 



The sediment built up within the stream channel through the late 1970s and 80s became a concern 

 because of its effects on the spawning bull trout population. In 1980, Montana Department of Fish, 

 Wildlife and Parks began sampling the substrate in Big Creek to determine the percentage of fine 



