Evaluation of Historical Sediment Deposition 



volcanic ash deposition, 

 ^yman Di^t^rbanggs 



1865-1929 . Distinct correlations between 

 natural disturbance events and changes in fine 

 sediment deposition in Whitefish Lake are dif- 

 ficult to make. By contrast, correlations be- 

 tween human activities in the basin and lake 

 sedimentation are more readily apparent. Prior 

 to the arrival of the earliest Europeans settlers in 

 the late 1880s, the Whitefish Lake watershed 

 was heavily forested and virtually undisturbed 

 by human activity. Human activities in the 

 watershed apparentiy were limited to an occa- 

 sional small Indian fishing encampment near 

 the outlet of Whitefish Lake (Trippett 1956, 

 Schafer and Engelter 1973). Mean sedimenta- 

 tion rates in Whitefish Lake during this pre- 

 settlement period were the lowest recorded over 

 the 125 year period of record. Between 1865 

 and 1886, the estimated mean sedimentation 

 rate was approximately 20 mg/cm7yr (See 

 Figure B-1). 



Due to the low sedimentation rate during 

 the pre- settlement period, the mean sedimenta- 

 tion rate shown in Figure B-1 spans a relatively 

 long time interval (21 years). Annual sedimen- 

 tation rates likely varied within this long inter- 

 val. However, I have no evidence to suspect that 

 large changes occurred during the period from 

 1865-1886. In the first place, the mean sedi- 

 mentation rate from 1865-1886 was compa- 

 rable to the subsequent rate from estimated 

 between 1886 and 19(X). Second, if some un- 

 known, natural disturbance event occurred and 

 resulted in large short-term changes in the seem- 

 ingly stable, pre-settlement sedimentation rate 

 then one would expect to see changes reflected 

 in the visual character of the sediment core. No 

 distinct visual changes were evident in the core 

 over the 30 year pre-settlement period. 



The sedimentation rate increased slightly 



during the period from 1886-1900, concurrent 

 with the 1894 flood and early logging activity 

 around Whitefish Lake. The earliest European 

 settlers arrived in the watershed in the late 

 1 880s (Schafer and Engelter 1973). These early 

 residents were primarily trappers and lumber- 

 men. A sawmill was constructed at the outlet of 

 Whitefish Lake in 1891. Small logging opera- 

 tions were concentrated at the southeast end of 

 the lake. Trees were cut, and pulled to the lake 

 with horses whereupon they were floated down 

 the lake, or pulled on sleds across the ice to the 

 sawmill. This early logging activity around the 

 lake may have contributed to the slight increase 

 in sedimentation rate recorded between 1886 

 and 1900. The 1894 flood also may have con- 

 tributed to this increase. 



The sedimentation rate increased dramati- 

 cally in the early 1900s, reaching a rate of 155 

 mg/cmVyr, representing a 7-8 fold increase 

 over background levels. This increased sedi- 

 mentation rate coincides with increased human 

 activities in the basin including construction of 

 a railroad line for the Great Northern Railroad 

 along the entire 7 mile southern shoreline of the 

 lake. The terrain along the south lakeshore is 

 steep in places, thus considerable earth moving, 

 and road bed leveling occurred along the lake- 

 shore. Rail preparations along the lake also 

 included blasting through bedrock, excavation 

 of a tunnel near the head of the lake, and 

 construction of a trestle and filling of Beaver 

 Bay on the lake's southwest shore. Most of the 

 construction occurred over a several year pe- 

 riod prior to the official opening of the railroad 

 in 1904. 



There is little doubt that substantial amounts 

 of sediment were dumped and/or washed into 

 Whitefish Lake during construction of the rail 

 line. This activity likely contributed to the sedi- 

 mentation increase measured in the lake core 

 during this period. In addition, early logging 

 activity around the lake during this time period 



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Flathead Basin Cooperative Program Final Report 



