The hydrologic characteristics of the Beaver 

 Lake analysis area mitigates the effects of 

 ir\creased water yield resulting from both 

 ^ natural and human-caused changes in the 

 * forest crown cover. As described in Chapter 

 III, the numerous pothole lakes are recharged 

 through groundwater inflow and outflow; 

 surface contribution from perennial and 

 intermittent streams is negligible. Field 

 review of these drainages revealed that these 

 features are nonscoured and ephemeral. 

 Consequently, they experience surface runoff 

 very infrequently and are not capable of 

 transporting upland-produced sediment to the 

 lake basins. To ensure protection of these 

 ' features, SMZs and equipment restriction 

 zones would be applied in areas most sensitive 

 to ground-disturbing activities. 



FINE-SEDIMENT 

 PRODUCTION 



BACKGROUND 



Land management activities, such as road 

 construction, livestock grazing, and timber 

 harvesting, can potentially increase levels of 

 fine-sediment delivery to streams and lakes if 

 not properly designed and mitigated. Numer- 

 ous studies have documented the effects of 

 suspended sediments on beneficial uses and 

 s salmonid fishes (MacDonald 1991, Cordone 

 and Kelly 1961, Sorensen et al., 1977). The 



primary effects are: 



i> 



iihf\ acting directly on free-living fish, either by 

 killing them, by reducing their growth rate 

 or resistance to disease, or both; 

 ^^r '' interfering with the development of eggs 

 and larvae; <^* ' ' 



modifying natural movements and migra- 

 tions of fish; and 



reducing the abundance of food organisms 

 available to the fish, such as aquatic inver- 

 tebrates and periphyton (Newcombe et al. 

 1991). 



Increased levels of fine-sediment deposition 

 have also been correlated with survival-to- 

 ^ emergence success of developing salmonid fry 

 (Stowell et al. 1983, Young et al. 1990). Fry 



survival-to-emergence rates is 80-90% when 

 fine sediments constitute less than 10% of a 

 redd; the rate drops to 15-55% when fines 

 exceed 30% (Rhinne and Neary, 1991). 



TIMBER HARVEST UNITS 



NO-ACTION ALTERNATIVE 



No timber-harvesting activities would occur, 

 therefore, no fine-sediment production would 

 occur. 



ACTION ALTERNATIVES A AND B 



Soil erosion from timber harvest units and 

 exposed soils occurs where the organic litter 

 layers have been removed and water accumu- 

 lates and flows. The areas most prone to 

 erosion include skid trails, landings, firelines, 

 and roads; however, off-site sediment delivery 

 can occur from harvest units as well. As water 

 concentrates and flows, energy is generated to 

 detach soil particles, initiating the erosion 

 process. Removal of duff and litter layers 

 increases erosion potential in the presence of 

 increased water and overland flow. Forest 

 organic matters, both living and dead, are 

 important in controlling soil erosion. Exces- 

 sive removal of vegetation, especially on steep 

 sideslopes with erodible soil types, has the 

 potential to increase erosion. 



The type of harvest method utilized can 

 mitigate erosion from timber harvest units. In 

 general, ground-based operations have the 

 potential to cause more localized impacts to 

 soils within harvest units and skid trails than 

 cable and helicopter yarding methods. Com- 

 paction and displacement are most likely to 

 occur on landings, temporary roads, and skid 

 trails. Designation of skid trails and imple- 

 mentation of appropriate BMPs through 

 enactment of the Timber Sale Contract clauses 

 can be used to reduce the occurrence and 

 severity of soil compaction and displacement 

 in both action alternatives. In addition, imple- 

 mentation of SMZs and equipment restriction 

 zones would be used in sensitive areas to filter 

 sediment derived from harvesting activities in 

 the units. Nonchannelized flow from units 

 would be controlled through the application of 



^^■{IV-18'r 



Stillwater State Forest • Beaver Lake Timber Sale Project 



