STREAMS 



First- and second-order interniittent and 

 ephemeral drainage features characterize the 

 Beaver Lake Project area, with the exception of 

 the main stem of Beaver Creek. These features 

 were formed as lingering valley ice melted, 

 creating topographic depressions and drain- 

 age features. The main difference between 

 ephemeral and intermittent channels is their 

 interaction with the water table. While inter- 

 mittent, effluent channels flow for only certain 

 times of the year, they receive water from 

 groundwater springs and surface runoff. 

 Ephemeral channels are considered influent; 

 having channels that are above the water table 

 at all times. They carry water only during and 

 immediately following a rainfall or precipita- 

 tion event and are not hydrologically con- 

 nected to the groundwater table. 



Intermittent and ephemeral channels in the 

 project area were reviewed to determine their 

 flow regime and sediment-delivery potential. 

 A majority of the stream courses identified on 

 the USGS Beaver Lake quadrangle as peren- 

 nial or intermittent streams are nonscoured 

 ephemeral features that do not produce sedi- 

 ment and show no indication of recent surface 

 flow. Small, isolated wetlands and draws 

 adjacent to most of the lakes in the analysis 

 area experience high water tables and serves 

 as groundwater discharge areas to the lake 

 basins. 



It is likely that since the retreat of continental 

 glaciers, many of these lakes were periodically 

 interconnected with surface water due to the 

 climatic variability that influenced groundwa- 

 ter table elevations. 



BEAVER CREEK 



Beaver Creek, the only perennial Class I 

 stream within the project area, is the principal 

 outlet of Beaver Lake. Peak flows occur 

 during the months of April and May in re- 

 sponse to groundwater recharge to Beaver 

 Lake and upland surface runoff generated 

 from the melting of the winter snowpack. 

 During the summer, fall, and winter months, 

 baseflows are maintained through groundwa- 



ter recharge, lake discharge, and seasonal 

 rains. 



Beaver Creek was field reviewed to assess the 

 potential effects of past and proposed activi- 

 ties on stream channel processes and function. 

 Channel surveys were completed according to 

 the Rosgen Stream Channel Classification 

 methodology. Pfankuch channel stability 

 ratings were completed in order to predict the 

 response of Beaver Creek to imposed water- 

 shed management activities such as timber 

 harvesting and road construction. 



• REACH 1 



The lower reach of Beaver Creek upstream 

 of the confluence with Whitefish Lake is 

 formed in sandy glacial till and outwash 

 deposits that have been sorted by glacial , 

 meltwater. The channel is characterized as 

 a moderately entrenched channel with bed 

 morphology dominated by fine to coarse- 

 grained cobbles and step-pool bedform 

 features (Rosgen B4 channel type). Coarse 

 woody debris (>4" dbh) is fairly abundant, 

 forming step features and small, unstable 

 debris jams. In general, banks are stable, 

 well vegetated with moss, birch, cedar, 

 spruce, equisetum, princess pine, and red 

 osier dogwood. There is some evidence of 

 isolated bank scour and erosion through- 

 out Reach One, which may account for the 

 accumulation and deposition of fine mmi 

 sediment in pools. Approximately 30% of ; 

 the channel substrate is comprised of fine 

 material less than 2 millimeters in diameter 

 (based on Wolman pebble-count data). . 

 Fine sediment deposition is most likely 

 being exacerbated through Reach 1 due to | 

 jn a small on-stream impoundment that has i 

 formed upstream of the railroad fill along f 

 the shoreline of Beaver Bay (Section 22). It 

 is likely that this small lake was connected 

 to Beaver Bay prior to construction of the 

 Burlington Northern Railroad. {Refer to 

 Table 111-12 - Beaver Creek Channel Character- 

 istics.) 



Chapter III: Affected Environment 



,v.^7^A.*,?r^«»:;.^ 



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