The largest identified sediment source is an irrigation ditch located on trust land in the Bear 

 Creek watershed. Large volumes of sediment were once delivered to Lower Bear Creek from 

 headcutting and gully erosion that occurred on the irrigation ditch during the last 40-50 years. 

 An estimated 650 cubic yards of fine materials were eroded out of the gully system and 

 transported directly to lower Bear Creek during this time. 



Increased water yields caused by the diversion of the discharge of Beaver Creek into the lower 

 reaches of Bear Creek have also contributed to instability. Lower Bear Creek is subjected to the 

 combined flows of Beaver Creek and Bear Creek during much of the year due to a lack of 

 headgate control at a diversion structure on Beaver Creek. Increased flow has the greatest 

 potential impact during peak runoff when the additional discharge to Bear Creek may result in 

 increased bank scour and channel degradation. 



Other identified sources of sediment in Beaver Creek and Bear Creek include the US Forest 

 Service Road #4325 and several lower standard roads located on private and State land. 

 Channel instability and sediment delivery is also evident due to extensive livestock grazing 

 and riparian vegetation clearing on private land downstream of the State ownership. 



Stream Channel Stability 



All stream channels and well-defined ephemeral drainage features within the proposed sale area 

 were inventoried and evaluated in the field in 1993 and 1999. Individual stream reaches were 

 delineated and classified using Rosgen's morphological descriptions (Rosgen 1996). Channel 

 conditions and stability were rated using the Pfankuch method outlined in Forest Hydrology Part 

 n, USPS 1974. 



Channel conditions on State ownership in Beaver Creek and Bear Creek were rated as being in 

 good to excellent condition. Both streams are dominated by reaches of B4 channels that were 

 evaluated as being in relatively stable condition. There is evidence of bank trampling from past 

 cattle use in the Bear Creek. However, in 1997, DNRC constructed a fenced riparian grazing 

 enclosure on a segment of Bear Creek that had been the most impacted. This reach was 

 evaluated in 1999, and it was determined that the streambank had re-vegetated and most of the 

 damage had recovered. Although there are still moderately high levels of fine sediment 

 deposition in both stream channels. 



Stream channel conditions in lower Bear Creek (downstream of the State ownership) were rated 

 as being in fair condition. The stream banks in lower Bear Creek have more active bank cutting 

 and are not as well vegetated with deeply rooted plants than the area upstream on USPS and 

 DNRC lands. This is partially due to the higher levels of cattle use in and around the stream. 

 The lower portions of the watershed are privately owned and it is more accessible and vulnerable 

 to cattle use than the more heavily forested public lands located upstream. The present stream 

 channel condition appears to be more stable than conditions reported in the recent past. This is 

 based on the remaining evidence of braided channels, small headcuts and bank scour and failure. 

 The current DNRC evaluations compared with evaluations conducted by the BLM in 1982 

 suggests that these channel features are stabilizing. 



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