HYD"RDLOGY 



crossings require additional BMP 

 work, and others need to be 

 replaced. Surface drainage needs to 

 be upgraded. Despite this, 

 reconnaissance identified no point 

 sources of fine-sediment delivery. 



Past timber harvesting and 

 associated road construction, 

 combined with vegetative recovery, 

 have led to a 4.9 percent increase 

 in water yield over an unharvested 

 condition in this watershed. The 

 allowable water yield increase is 12 

 percent. 



ALTERNATIVE EFFECTS 

 DIRECT AND INDIRECT EFFECTS 



• Direct ami Indirect ^ffectn qfA'o-^lction 

 . Ulernatice ,1 on Ilydrology 



This alternative would have no 

 direct effects to sediment 

 delivery or water quality beyond 

 those currently occurring. An 

 increased risk of sediment 

 delivery to streams from crossings 

 that do not meet BMPs would 

 continue until other funding 

 becomes available to repair them. 



• Direct and Indirect ^ffectji qf Action 

 .llternatice B on Hydrology 



This alternative would: 



- replace several stream crossings 

 in the Dog Creek watershed and 

 along the proposed haul route; 



- construct .3 mile of temporary 

 road in Section 28, including 

 the installation of a culvert on 

 a perennial stream; and 



- improve drainage from the road 

 surface. 



All pertinent laws, rules, and 

 BMPs, including erosion-control 

 measures, would be applied to all 

 roadwork and harvesting activities 

 to minimize the risk of sediment 

 delivery to draws and streams. 

 The 0.3 mile of proposed temporary 

 roads would be reclaimed 

 immediately after harvesting 

 activities are completed. The 

 reclaimed road would pose an 



increased risk of sediment 

 delivery until the bare soil 

 revegetates . On the temporary 

 road in Section 28, little or no 

 disturbance to the creek banks and 

 bed would occur while installing a 

 temporary stream crossing in the 

 perennial stream. In the long 

 term, the risk of sediment 

 delivery to streams would be 

 reduced from current conditions. 



Action Alternative B would 

 increase the annual water yield in 

 this watershed by 2 . 9 percent over 

 the current level. This level of 

 increase would not be sufficient 

 to create unstable channels. 



CUMULATIVE EFFECTS 



• Cumulative Ii^ect* qfJKo-, Iction Alternatice 

 »1 on Hydrology 



All existing sources of sediment 

 would continue to recover or 

 degrade as dictated by natural and 

 preexisting conditions until a 

 source of funding is available to 

 repair them. Sediment loads would 

 remain at or near present levels. 

 Harvest units of the past would 

 continue to revegetate and move 

 closer to premanagement levels of 

 water use and snowpack 

 distribution. 



• Cumulative Effects qf, Iction , llternatice li on 

 Hydrology 



The sediment generated from 

 replacing an existing culvert 

 would increase the total sediment 

 load in Dog Creek while the 

 culvert is being replaced. The 

 installation and improvement of 

 erosion-control features on 

 existing roads would also affect 

 the cumulative sediment delivery 

 in Dog Creek by exposing bare 

 soil, though applying BMPs during 

 this work would make increased 

 sediment loads unlikely. As these 

 sites stabilize and revegetate, 

 the sediment levels would return 

 to the level of preactivity. Over 

 the long term, cumulative sediment 

 delivery to Dog Creek would likely 



Chapter III— Existing Environment and Environmental Consequences page III-ll 



