Cottonwood Creek 



Restoration objectives: improve degraded habitat; eliminate fish losses to irrigation 

 ditches; restore instream flows and migration corridors for native fish. 



Project Summary 



Cottonwood Creek flows fi"om Cottonwood Lakes 1 6-miles to its junction with 

 the middle Blackfoot River entering at river mile 43 with a base flow of ~15 cfs. 

 Cottonwood Creek supports bull trout, genetically pure WSCT, rainbow trout, brown 

 trout and brook trout. WSCT and bull trout dominate the headwaters. Rainbow trout 

 inhabit the lower mile of stream while brook trout and brown trout dominate middle 

 stream reaches. 



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Figure 18. Stage discharge relationship for the Dreyer ditch on 

 Cottonwood Creek, May 2005. 



In 2003, we 

 also assessed a 

 road-crossing 

 problem related to 

 an undersized 



culvert at stream 

 mile 15.9. This 

 undersized and 



perched culvert 



causes severe 



channel 



downcutting and 

 high erosion 



immediately below 

 the culvert, along 

 with aggradation 

 below the incised 

 reach (Dave 



Rosgen, personal 

 communication). 

 This instability 



appears to 



contribute to the 

 loss of surface flows 

 during base flow 

 periods and 



isolation of fish 

 between the 



dewatered section 

 and the perched 

 culvert. We 



measured a decrease 

 in flows fi-om 0.4 



cfs to the complete loss of surface flow over a distance of 765' in September 2003. We 

 fiirther identified road drainage into this portion of Cottonwood Creek. In 2005, we also 



035 



S 



1096 1997 1998 1999 2000 2001 2002 2003 2004 2005 



Figure 19. CPUE for native trout in Cottonwood Creek at mile 

 12.0, 1996-2005. 



30 



