17 ‎(3)‎

• Board Meeting Date: 1/23/2008
• Description: ISF Section - Injury with Mitigation - Case No. 3-99CW34; application of Charles E. Nearburg
• Board Meetings - Doc Type: Memo

Draft - Trout Creek Bioassessmellt

6.1 Changes in Flow Regime

Station 1

Station 1 represents conditions typical of Trout Creek prior to any rehabilitation/restoration
activiti~s. The channel is braided, with four channels carrying flow. Table 4 summarizes the
flow characteristics of the char:m.el at this location under both CWCB minimum instream flow
levels and flow levels reflecting the proposed 4 cfs diversion. The effect of the proposed
diversion on CWCB instream flow levels in the channel can be seen graphically in Figures 3 and

4.

Table 4

Effect of 4 cfs Diversion on CWCB Instream Flow Criteria

Station 1 (Reference Condition)
(Top Width at Bankfull = 84_1 ft.)
(Wetted Perimeter at Bankfull = 85.4 fL)
Depth Velocity Wetted Perimeter
Characteristics Characteristics Characteristics
Average %.of Avel<lge %of % Wetted %of
Depth (ft.) eWCS Velocity (ft./sec.) CWCS Perimeter CWCS
(CWCB Criteria (CWCB Criteria = Criteria (CWCB Criteria
Criteria =0_84 ft.) 1.0 ft./sec.) Criteria :>70 %)
Current ewcs
lnstream Row 0.27 32 1.34 134 49% 70
Right 15 cfs
Discharge after .... .....---_.-.
Proposed 0.27 32 1j:i..~m~ ~.13r --....,.....~-.- ~-S7%. 53
Diversion: 11 cfs
Current CWCS
lnstream Flow 0.39 46 1.72 172 62% 89
Right 35 cfs
Discharge after
Proposed 0.37 44 1.65 165 60% ., 86
Diversion: 31 efs

It can be seen that flow conditions present in this un-rehabilitated section ofthe stre3D1 can
generally be expected to not meet CWCB standards at the 15 cfs winter minimum instream flow.
Only one of the CWCB criteria is met at this flow level. Under a reduced flow of 11 cfs the
water level in the channel drops only 0.08 feet. The one criterion met at the 15 cfs level is still
met under the reduced flow.

32

F:\ W\VEWEf\2000\981-143\J3ioassessment\Final Report\Report.doc