LASSEN LODGE HYDROELECTRIC PROJECT - Battle Creek… · 07/07/2015 · Spawner Capacity ... Map of...

Applied Research in Fisheries, Restoration, and Ecology.

Cramer Fish Sciences 600 NW Fariss Road Gresham, OR 97030

503-491-9577 www.fishsciences.net

LASSEN LODGE HYDROELECTRIC PROJECT Fish Habitat Survey at 34 cfs on the Project Reach, South Fork Battle Creek

Prepared for:

Rugraw, LLC.

Prepared by:

Kirsten Sellheim

Paul J. Haverkamp

Steven P. Cramer

Kevin Ceder

June 26, 2015

20150707-5087 FERC PDF (Unofficial) 7/7/2015 1:14:39 PM

Lassen Lodge Project Reach Survey at 34 cfs

Cramer Fish Sciences i

TABLE OF CONTENTS List of Figures .............................................................................................................................. iii

List of Tables ................................................................................................................................ v

Executive Summary ......................................................................................................................... 6

Introduction .................................................................................................................................... 8

Project Description ..................................................................................................................... 8

Survey Area ................................................................................................................................. 9

Methods ........................................................................................................................................ 10

Rearing habitat survey .............................................................................................................. 10

Habitat Type .......................................................................................................................... 11

Active Channel Width ........................................................................................................... 12

Average Wetted Width ......................................................................................................... 12

Active Channel Height ........................................................................................................... 12

Depth and Velocity................................................................................................................ 12

Substrate Classification ......................................................................................................... 13

Wood Complexity.................................................................................................................. 13

Gradient ................................................................................................................................ 14

Total Length .......................................................................................................................... 14

Constraint Type ..................................................................................................................... 14

Photo Documentation........................................................................................................... 14

Flow Transects ...................................................................................................................... 14

Spawning Habitat Survey .......................................................................................................... 14

Estimation of Fish Carrying Capacity ........................................................................................ 14

Passage Barriers ........................................................................................................................ 15

Results ........................................................................................................................................... 15

Flow During the Survey ......................................................................................................... 15

Flow-Based Changes in Habitat Attributes ............................................................................... 16

Rearing Habitat Attributes .................................................................................................... 16

Spawning Habitat Attributes ................................................................................................. 27



Cramer Fish Sciences ii

Estimated Production Potential ................................................................................................ 29

Predicted vs. Observed Rearing Capacities .......................................................................... 29

Spawner Capacity .................................................................................................................. 30

Uncertainty in Measurements and Predictions ........................................................................ 31

Predicted vs. Observed Channel Unit Dimensions ............................................................... 31

Effect of Measuring Multiple Transects per Unit on Estimation of Rearing Capacity .......... 34

Discussion...................................................................................................................................... 36

Flow-based Changes in Habitat ................................................................................................ 36

Rearing Habitat Attributes .................................................................................................... 36

Spawning Habitat Attributes ................................................................................................. 37

Predicted vs. Observed Carrying Capacities ............................................................................. 37

Measured Production Potential ............................................................................................ 37

Comparison of Measured and Predicted Production Potential ........................................... 39

Predicted vs. observed channel unit dimensions ..................................................................... 40

Measurement and Prediction Uncertainty ............................................................................... 41

Existing Fish Passage Impediments ............................................................................................... 41

Measurement Results ............................................................................................................... 41

Discussion.................................................................................................................................. 42

References Cited ........................................................................................................................... 44

Appendix A: Site Photos ................................................................................................................ 47

Appendix B: Data Summaries ....................................................................................................... 50

Appendix C: Spawning Gravel Patch Data .................................................................................... 54

Appendix D: Flow Transect Cross Sections ................................................................................... 55

Appendix E. Predicted inundation at channel cross sections ...................................................... 59



Cramer Fish Sciences iii

List of Figures

Figure 1. Topographic map of study area on the South Fork of Battle Creek, showing location of notable stream features. Angel Falls is the established limit of anadromy. ................................. 9 Figure 2. Map of riffle and pool channel units re-sampled from July 2013 survey. Channel unit numbers correspond to those established in the first survey (Sellheim and Cramer 2013). Width, depths, and velocities were measured across three transects at each channel. The LLHP powerhouse/tailrace is proposed to be located at channel unit 4. ............................................. 11 Figure 3. Box plots comparing active channel widths and average wetted widths in pools and riffles in units sampled at flows of 13 and 34 cfs. In both pools and riffles, average wetted widths were significantly higher under higher streamflow (both p < 0.05). Average active channel widths were not significantly for pools (p > 0.05), but riffle active channel width measurements were significantly lower at 34 cfs than at 13 cfs (p < 0.05). See Appendix B Table B-1. ................................................................................................................................................ 17 Figure 4. Measured average wetted width at 13 cfs in 2013 and 34 cfs in 2015. Widths were measured in each unit at one transect in 2013 and three transects in 2015. ............................. 18 Figure 5. Active channel width measured at 13 cfs in 2013 and 34 cfs in 2015. Widths were measured in each unit at one transect in 2013 and three transects in 2015. ............................. 19 Figure 6. Box plots comparing active channel height and maximum depth in pools and average depth in riffles in units sampled both at 13 cfs in 2013 and 34 cfs in 2015. Depths did not differ significantly for either pools or riffles between the two years (both p > 0.05). Pool active channel heights were not significantly different (p > 0.05) but riffles were significantly different (p = 0.05) in any of the substrate categories...................................................................................................................... 26 Figure 13. Measured areas of spawning gravel patches at 13 cfs in 2013 and 34 cfs in 2015. ... 27 Figure 14. Measured depths of spawning gravel patches at 13 cfs in 2013 and 34 cfs in 2015. . 28 Figure 15. Measured velocities of spawning gravel patches at 13 cfs in 2013 and 34 cfs in 2015........................................................................................................................................................ 29 Figure 16. Comparison of mean wetted width (m) measured for individual channel units in 2015 (Observed axis) versus widths that were predicted (Predicted axis) for 34 cfs based on the



Cramer Fish Sciences iv

hydraulic geometry methods reported by Cramer and Ceder (2013). The black line is the 1:1 line where observed and predicted are equal. ............................................................................. 32 Figure 17. Comparison of depths (m) measured for individual channel units in 2015 (Observed axis) versus depths predicted (Predicted axis) for 34 cfs based on the hydraulic geometry methods reported by Cramer and Ceder (2013). The black line is the 1:1 line where observed and predicted are equal. ............................................................................................................... 33 Figure 18. Comparison of measured channel widths (m) (Observed axis) to those that were predicted (Predicted axis) for the six cross section profiles. Predictions were based on the hydraulic geometry methods reported by Cramer and Ceder (2013). The black line is the 1:1 line where observed and predicted values are equal. Each red and blue line is a trajectory of a channel cross section. ................................................................................................................... 34 Figure 19. Values of the depth scalar by which parr densities are multiplied in the UCM to estimate parr capacity of a stream channel unit. ......................................................................... 40 Figure 20. Photograph of Powerhouse Falls (Channel Unit 4) from Parkinson (2012) taken on December 14, 2002 at a flow later estimated to be 180 cfs (200 cfs was preliminary). This falls is immediately below the proposed powerhouse/tailrace. Note the high horizontal velocity at the base of the falls. ............................................................................................................................ 43 Figure D-1. Cross sectional profile of Battle Creek in the area containing logger 1. …………………555 Figure D-2. Cross sectional profile of Battle Creek in the area containing logger 2. ................... 56 Figure D-3. Cross sectional profile of Battle Creek in the area containing logger 3. ................. 566 Figure D-4. Cross sectional profile of Battle Creek in the area containing logger 4. ................. 577 Figure D-5. Cross sectional profile of Battle Creek in the area containing logger 5. ................. 577 Figure D-6. Cross sectional profile of Battle Creek in the area containing logger 6. ................. 588 Figure E-1. Comparisons of predicted and observed widths across the channel for a range of elevations at each of the six channel cross sections where pressure transducers were placed to enable continuous monitoring of depth and temperature across a range of flows. 599



Cramer Fish Sciences v

List of Tables

Table 1. Riffle and pool geomorphic channel type descriptions. ................................................. 12 Table 2. Substrate size classes. ..................................................................................................... 13 Table 3. Wood complexity rating definitions. .............................................................................. 13 Table 4. Calculated flows at each of the six cross sections where pressure transducers were installed and detailed measurements depth were completed at width increments of ≤ 3 feet. 16 Table 5. Comparison of the parr rearing capacity for habitat measured at 13 cfs to those predicted and measured for 34 cfs. Predicted values are from modeling output of Cramer and Ceder (2013). All capacities were estimated with the Unit Characteristic Method (UCM). ....... 30 Table 6. Measurements of spawning patches identified during field survey. These are compared to the minimum requirements for target species to identify their suitability for spawning at 34 cfs. Only one gravel patch was found in unit 16 in 2013 and no patches were found in unit 38 in 2013. ............................................................................................................... 30 Table 7. Estimates of maximum and minimum rearing capacities calculated if only one transect were measured and the mean capacity estimated by averaging all three transects in each channel unit. The minimum uses all the worst case transects and the maximum uses all the best case transects. Chinook values pertain to either spring-run or fall-run. ............................. 35 Table 8. Comparison of coefficients of variation for fish rearing capacities in pools and riffles, compared between the 2013 and 2015 surveys. ......................................................................... 35 Table 9. Measured values of passage barriers along Battle Creek. Barriers with a ratio of less than 1.25 for jump pool depth to the jump height are likely to be impassable, based on the work of Powers and Orsborn (1985). This ratio may not be as limiting at jump heights of 1 m or less if Steelhead Trout can achieve sufficient vertical velocity. ................................................... 42 Table B-1. Width and depth dimensions of channel units measured in 2013 and mean measurements in 2015. ................................................................................................................ 50 Table B-2. Additional channel unit features measured in 2013 and mean measurements in 2015. ............................................................................................................................................. 51 Table B-3. Substrate (mean in 2015) percentages at sampled units in 2013 and 2015. ............. 52 Table B-4. Comparison of measurements taken in 2013 and mean measurements in 2015. ..... 53

Table C-1. Data recorded for each spawning gravel patch identified during survey. Note that only patches that were fully submerged (in units 4, 8, 16 (both), 35, 38 (both), 49, and 50) were analyzed in the results. ................................................................................................................. 54



Cramer Fish Sciences 6

EXECUTIVE SUMMARY

Cramer Fish Sciences (CFS) surveyed salmonid spawning and rearing habitat in the proposed Lassen Lodge Hydroelectric Project reach of the South Fork of Battle Creek at 34 cubic feet per second (cfs) on 18-21 March 2015. The survey covered 1.6 miles of the stream (referred to as the bypass reach) where flows will be reduced by the amount of flow diverted to produce electricity. Channel dimensions (length, width, depth, and velocity) from this survey were to be compared with those measured at 13 cfs in July 2013 to determine how habitat attributes that influence carrying capacity for spring-run and fall-run Chinook Salmon, Oncorhynchus tshawytsha, and summer Steelhead Trout and resident Rainbow Trout, O. mykiss, within the bypass reach will respond to differences in flow. There is no capacity for winter-run Chinook in the bypass reach, because the temperatures regime during the time of their spawning in May and June exceeds the lethal limit for egg incubation. The surveyed reach extends from Angel Falls (RM 22.2) downstream to RM 20.6, where water flowing through the powerhouse/tailrace will rejoin flow in the stream channel, and the project will have no effect on stream flows below that point.

Wetted width of channel units increased significantly (p < 0.05) under higher flows for both pool and riffle habitat types, but differences in depth were not significant for either pool or riffle habitat types. There was substantial variation between channel units in how much the width and depth changed. Widths increased by an average 50% (3.5 m) for pools, and 40% (3.1m) for riffles. Velocities were significantly higher (p < 0.05) in riffles at 34 cfs, and also became detectable in pools (mean = 0.15 m/s). Causes for variability in measured changes likely include measurement error and increased gravel accumulation in the main channel following two winters of low flow in this high gradient stream reach.

Eight patches of gravel suitably sized for Chinook Salmon or Steelhead and Rainbow Trout spawning were found in the 20 channel units surveyed. All patches met the minimum depth and area requirements for spawning of Steelhead and Rainbow Trout, but only one gravel patch had sufficient velocity to meet minimum criteria. Suitable velocities were generally not present over large gravel patches even at a flow of 34 cfs. Only one patch had sufficient depth and area for a single pair of Chinook Salmon to spawn, but the patch was downstream of the proposed powerhouse/tailrace, and thus outside the bypass reach.

The position and size of gravel patches also changed substantially between 2013 and 2015 in several channel units. Some patches present in 2013 were absent in 2015 and new patches were present in 2015 that were absent in 2013. Substantial changes in spawnable gravel patches between 2013 and 2015 indicate these gravels are frequently mobilized, making these gravel patches a risky location for salmon and trout to deposit eggs.

In contrast to wetted widths, active channel widths of riffles decreased significantly (p < 0.05) by 19% (2.5 m), while active channel widths of pools did not change significantly when comparing the two flows. There was no significant difference (p > 0.05) in active channel heights for pools between surveys, but these heights were significantly greater (p < 0.05) in riffles during the 2015 survey. Active channel dimensions should remain relatively stationary,




so the change is likely due to errors in distinguishing active channel marks, and to the effect of averaging three channel widths and heights per unit in 2015, rather than the one per unit measured in 2013.

Rearing salmonid (parr) capacity at 34 cfs, estimated with the Unit Characteristic Method (UCM) was 2,789 Chinook Salmon parr and 3,190 Steelhead and Rainbow Trout parr. The range between maximum and minimum estimates for rearing capacity in pools was 80% to 122% of the mean, and in riffles was 68% to 126% of the mean.

Habitat conditions measured in 2015 at 34 cfs again confirm the findings of Cramer and Ceder (2013) that spawning capacity was the most limiting factor for Chinook Salmon, while rearing capacity was the most limiting factor for Steelhead and Rainbow Trout. For Chinook Salmon, the one redd capacity would produce an estimated 218 parr, which is only 17% of the estimated reach rearing capacity of 1,298 parr at a simulated low-season flow of 10 cfs (Cramer and Ceder 2013). The average flow for the month of lowest flow is 8 cfs, and flow dropped to zero in 2014. In contrast to Chinook Salmon, spawning capacity for Steelhead Trout spawning at only 10 cfs can produce roughly 10 times more parr (13,092 parr) than the typical low-flow rearing capacity (1,407 parr) can support (Cramer and Ceder 2013). At 34 cfs, the capacity for Steelhead Trout rearing increased only to 3,190 parr, which is still far less than 13,092 parr that could be produced by Steelhead spawning capacity at only 10 cfs. Capacity for Rainbow Trout spawning would exceed that for Steelhead, but rearing capacities would be the same.

Potential for upstream passage of adult salmonids was assessed at seven potential barriers to upstream passage. Seven barriers were found to be unpassable at 34 cfs due to inadequate depth required to leap the height over the barrier. The most significant barrier occurred immediately below the proposed powerhouse/tailrace location. This barrier, named Powerhouse Falls, was 8 feet high and only 1.5 feet deep at its base. This falls was measured previously at 180 cfs in December, 2002, and was also impassible at that flow. This falls is likely to prevent anadromous fish from entering the project reach.

Comparison of measurements and prediction from the two surveys (13 cfs and 34 cfs) enable us to evaluate uncertainty in values of channel dimensions and fish production potential. Measurements of active channel heights and widths proved inconsistent between the first and second survey (when they should not have changed), and errors in those determinations were propagated into the predictions of water levels at different flows. The increase in widths at 34 cfs was under predicted and depths were over predicted. These prediction errors for habitat metrics resulted in over prediction of the capacity for juvenile rearing. The estimated capacity at 34 cfs was only 49% of what was predicted for Chinook Salmon and 48% of what was predicted for Steelhead and Rainbow Trout.

Dimensions of channel units were measured differently in the two surveys, with the 2015 survey better accounting for variance in channel dimensions. During the first survey in July 2013, dimensions were measured across one transect in each of the 51 channel units in the reach. In the March 2015 survey, dimensions were measured at three transects within each of the 10 pools and 10 riffles sampled. After these measurements were used to estimate rearing




capacities, the project team found the 2015 sampling strategy reduced the coefficient of variation for fish capacity by 14 percentage points for Chinook Salmon in pools, 16 percentage points for Steelhead in pools, and 32 percentage points for Chinook Salmon and Steelhead Trout in riffles.

Continuous depth monitoring stations were installed with HOBO pressure transducers at three pools and three riffles, and cross sections were measured at each location at 3-foot increments of width, and no more than 6-inch increments of elevation, continuing up to 3 feet above the water surface level on each bank. These stations will provide a continuous record of depth and temperature as flow changes, and continuous flow will be monitored at several locations by Rugraw, LLC.

INTRODUCTION

Project Description

This report describes findings from a stream habitat survey in March 2015 and associated analysis to estimate how channel dimensions and production potential for spring- and fall-run Chinook Salmon, Steelhead Trout, and resident Rainbow Trout will change at different flow levels in the upper South Fork of Battle Creek. The stream reach of interest is within the boundaries of the proposed Lassen Lodge Hydroelectric Project (LLHP) located on the upper South Fork of Battle Creek, approximately 1.5 miles west of Mineral, Tehama County, California. The proposed project is being developed by Rugraw, LLC and will produce an estimated 25,000,000 kilowatt hours of electricity annually (Rugraw, LLC 2012). The LLHP project is designed to divert a portion of stream flow into a penstock at RM 23, above Angel Falls (RM 22.2), and deliver the water to a powerhouse/tailrace at RM 20.6 (Figure 1). All flow will return to the stream at the tailrace at that point, located 1.7 miles upstream of Panther Grade (RM 18.9), which is a putative barrier to upstream fish migration, and the upper project limit of the Battle Creek Salmon and Steelhead Restoration Project. Flows would be unaltered downstream of the powerhouse/tailrace, and no flows would be diverted upstream for power generation during the low flow season, generally early summer to late fall. Results of the stream habitat study described in this report will be used to identify minimum flow prescriptions to be maintained in the active channel within the project reach.

The survey results reported here are the second set of habitat measurements completed for that portion of the LLHP project reach that extends from Angel Falls to the proposed powerhouse/tailrace location 1.6 miles downstream (Figure 1). The first survey was completed July 3-4, 2013 at a flow of 13 cfs, and this second survey was completed March 18-21, 2015 at a flow of 34 cfs. In the first survey, habitat attributes of depth, width, velocity and substrate composition were measured in each of the 51 channel units composing the study reach (Sellheim and Cramer 2013), and the measurements were used to predict the carrying capacity of the reach for juvenile rearing and adult spawning of Chinook Salmon, Steelhead Trout, and resident Rainbow Trout (Cramer and Ceder 2013). There is no capacity for winter-run Chinook,




because temperatures during the May and June spawning season are lethal to incubating eggs. Additionally, active channel dimensions were used to describe the hydraulic geometry of the channel and predict how depth, width, and velocity in each channel unit would change over a range of flows. The second survey, reported here, repeated the survey on a subset of the channel units at a higher flow (34 cfs), and recorded additional measurements to meet the following objectives:

1. Quantify key attributes of habitat for juvenile rearing and adult spawning at a flow of approximately 30 cfs (mean flow was 34 cfs during survey).

2. Estimate rearing and spawning capacity at ~30 cfs for spring- and fall-run Chinook Salmon, Steelhead Trout, and resident Rainbow Trout.

3. Determine the accuracy of predictions developed by Cramer and Ceder (2013) for response of channel dimensions to changes in flow.

4. Determine the repeatability and sampling error inherent in the channel attributes being measured.

5. Measure jump pool depth and jump height necessary for adult salmonids to pass locations that may impede upstream migration.

Figure 1. Topographic map of study area on the South Fork of Battle Creek, showing location of notable stream features. Angel Falls is the established limit of anadromy.

Survey Area

The LLHP project area is located on private land just north of Highway 36, and 1.5 miles west of Mineral, California. The upper South Fork of Battle Creek flows through the property in a constrained valley characterized by steep slopes on both sides of a narrow stream channel with substrate dominated by large boulders. Stream habitat within the portion of the bypass reach between the powerhouse/tailrace and Angel Falls (RM 20.6 to RM 22.2) is dominated by fast-water habitats (cascades, rapids, and riffles) that compose over 80% of surface area, while pools compose about 15% of surface area (Sellheim and Cramer 2013). The reach has 5% or




greater gradient and flows through a steeply confined valley. There is a near absence of woody debris, and all pools are formed by boulder dams. Gravel suitable for spawning was found in small patches (average area of 15 m2; range 5-46 m2) distributed throughout the reach. Sixty-four percent of the gravel patch area was within the wetted channel. The temperature and flow regime in the project reach support resident Rainbow Trout, which is the only fish species observed in the reach during the initial stream habitat and snorkel survey (Sellheim and Cramer 2013), and the only salmonid found above Panther Grade (RM 18.9) during electrofishing surveys by the USFWS (Brown et al. 2005). Natural streamflow in this reach varies between a median flow of 129 cfs during May (typical month of peak flow) to medians of only 9 cfs in September and 8 cfs in October with low flows minimums in recent years often reaching 3 cfs and even down to no flow in periods of Fall 2014. There is one spring, noted as Spring #4 in the Base Streamflow Study Parkinson and Rugraw, LLC 2014) located at RM 20.84, 0.24RM above the powerhouse/tailrace measured at 0.3 cfs in October 2014 that is the only detectable source of year-round surface inflow between Angel Falls and the powerhouse/tailrace. Although daily maximum temperatures up to 75°F (24°C) have been measured in this reach, typically summer temperatures are warmest above Angel Falls and the Diversion Structure where the stream flows through a large meadow, and then cools as the stream flows down through the canyon where the project is located. At the proposed powerhouse/tailrace location, the mean value of the 7-day maximum of average daily temperatures is 65°F (18.3°C). Stream surveys revealed substantial inflows from springs near Panther Grade (downstream of the project) that added about 14 cfs of 49°F water to the 13 cfs in South Fork Battle Creek above Panther Grade 2013. The Base Streamflow Study (Parkinson and Rugraw, 2014) goes into more detail of the large spring inflows in the vicinity of Panther Grade far below the project reach occurring at periods of even no flow within the project reach. These spring inflows dramatically increase the suitability of habitat for anadromous salmonids in the South Fork Battle Creek below Panther Grade, compared to that above, during the low flow season.

METHODS

Rearing habitat survey

Stream channel attributes were measured in 10 riffles and 10 pools (Figure 2) on March 18-21, 2015 at a streamflow of approximately 34 cfs (0.96 m3/s). Locations of selected riffles and pools, determined during the first survey of the bypass reach, were pre-loaded onto a Garmin eTrex 20 GPS unit and the crew used these points to navigate along Battle Creek to each location. Three transects were taken at each riffle and pool, at approximately one quarter of the total habitat unit distance from the upstream extent, one half of the total distance, and three quarters of the total distance. Water temperature (°C) and dissolved oxygen (mg/l and %) were measured two times each day.




Figure 2. Map of riffle and pool channel units re-sampled from July 2013 survey. Channel unit numbers correspond to those established in the first survey (Sellheim and Cramer 2013). Width, depths, and velocities were measured across three transects at each channel. The LLHP powerhouse/tailrace is proposed to be located at channel unit 4.

For each transect, the following measures were collected: date, time, habitat type, habitat unit number (based on previous survey), GPS point, photos, total length, depth (maximum depth if a pool), substrate percentages, depth and velocity at three points at 1/4, 1/2, and 3/4 of the channel width along the transect, wood complexity, active channel height, active channel width, gradient, average wetted width, impassable barrier, and constraint type. These attributes are described further below.

Habitat Type

The previous study classified the study reach into geomorphic channel unit types. For this analysis, only riffles and pools were of interest (Table 1). Channel units are defined as relatively homogeneous lengths of the stream that are classified by channel bed form, flow characteristics, and water surface slope. With some exceptions, channel geomorphic units are defined to be at least as long as the active channel is wide. Riffle and pool unit data collected during the survey is summarized in Appendix B.




Table 1. Riffle and pool geomorphic channel type descriptions.

Geomorphic Channel Unit Type Description

Pool A section of stream channel where water is impounded within a closed topographical depression. A pool would still have residual water depth if flow ceased. Pools are typically created when fluvial processes such as scour associated with a channel obstruction form depressions in the channel bed. The scour forms a depression which acts as a basin that would continue to hold water if there was no flow. Some pools are created by impoundments at the tail end, such as boulders, a debris flow, a log jam, or a beaver dam.

Riffle Fast, shallow flow with surface turbulence over submerged or partially submerged substrates. Generally broad, uniform cross section. Low gradient; usually 0.5-2.0% slope, rarely up to 6%. Some riffles may contain numerous sub-unit sized pools or pocket water created by scour associated with boulders, wood, or stream bed dunes and ridges. In these instances, sub-unit sized pools comprise 20% or more of the total unit area. Other protocols might classify these as pocket water, but in our case, these are boulder riffles (i.e. riffles with boulders as dominant substrate).

Active Channel Width

Active channel width (m) was measured at three transects across each channel unit as the distance across channel at "bank full" flow. Bank full flow is the level the stream flow attains every 2 years on average, and is often visible as a line above which vegetation starts or as a break point in slope. The boundary of the active channel was sometimes difficult to determine, and the project team used features listed above or high water marks to distinguish the boundary.

Average Wetted Width

Average width of wetted channel (m) was measured at each of three transects per unit using a laser rangefinder.

Active Channel Height

Active channel height (m) was measured with a stadia rod and a clinometer to measure the distance between bank full height and the water surface.

Depth and Velocity

Stream depth and velocity were measured at three equidistant locations along each transect using a Marsh-McBirney FloMate velocitimeter and a top-setting rod. For stream depths less than 0.6m, the project team measured velocity at 60% of the water column; for stream depths greater than 0.6m, the project team measured velocity at 20% and 80% of the water column, and then took the average of the two values.




Substrate Classification

For each channel unit, the project team classified the relative proportion of substrate contained in the wetted channel for the following size classes: fines, gravel, cobble, boulder, bedrock. See Table 2 for the size ranges of each class. Percentage composition was visually estimated to the nearest 5%. We further divided gravel into three subclasses roughly comparable to the size of marbles (small), golf balls (medium), and baseballs (large).

Table 2. Substrate size classes.

Size class Size range (mm)

Fines < 2

Gravel 2 - 60

Small 2 - 20

Medium 21 - 40

Large 41 - 60

Cobble 61 - 256

Boulders >256

Bedrock n/a

Wood Complexity

We assigned a wood complexity rating (1-5) to each channel unit, with a rating of 5 as the most complex. Table 3 provides a detailed description of each rating category.

Table 3. Wood complexity rating definitions.

Wood Complexity Rating Definition

1 Wood debris absent or very low

2 Wood present, but contributes little to habitat complexity. Small pieces creating little cover.

3 Wood present as combination of single pieces and small accumulations. Providing cover and some complex habitat at low to moderate discharge.

4 Wood present with medium and large pieces comprising accumulations and debris jams that incorporate smaller root wads and branches. Good cover for fish over most flow levels.

5

Wood present as large single pieces, accumulations, and jams that trap large amounts of additional material and create a variety of cover and refuge habitats. Woody debris providing excellent persistent and complex habitat. Complex flow patterns will exist at all discharge levels.




Gradient

For most channel units, the project team estimated channel gradient (% slope) at each of the three transect locations. If a channel unit was very short, a gradient measure was taken at the upstream and downstream end and these were averaged and applied to all three transects.

Total Length

Because the project team re-visited previously measured channel units, total lengths from the previous survey were used.

Constraint Type

Within each transect, the project team recorded the factor that constrained the channel (hillslope, bedrock, or terrace).

Photo Documentation

For each transect, a photo was taken of the upstream and downstream view, as well as any other potentially informative features (channel splits, pocket water in boulder riffles, fish, etc.). Representative photos are provided in Appendix 1. These photos were taken to provide a record for any estimates or additional measurements that were deemed useful after the survey.

Flow Transects

The project team took detailed measurements at six stream cross sections where pressure transducers were later installed to provide a continuous record of changes in depth and temperature as flow changes. Depth was measured at each location for 3-foot increments of width, not to be spaced at greater than 6-inch increments of elevation, continuing up to 3 feet above the water surface level on each bank. Flow will be monitored continuously at several locations by Rugraw, LLC.

Spawning Habitat Survey

The project team also measured depths and velocities at spawnable gravel patches within the units surveyed. These measurements were compared with both the measured and predicted values from the initial survey (July 2013). These submerged gravel patches (listed in Appendix 3) were measured for length, width (average of three measurements), and substrate composition. Depth of each patch was measured in three locations (upstream, middle, and downstream), and velocity was measured at 60% depth near the center of the patch. Measurement protocols were the same as the first survey, except that gravel patches were measured higher than two feet above the water surface.

Estimation of Fish Carrying Capacity

As described by Cramer and Ceder (2013), the project team again used the Unit Characteristic Method (UCM) to estimate fish carrying capacity in the study reach. Formulation of the UCM to




predict carrying capacity is based first on consistent differences that are found in densities of parr between types of channel units (ie. pool, riffle, rapid etc.). Further, parr densities within a specific type of channel unit are positively correlated to depth and cover complexity, and negatively correlated to fine sediment and temperature above their optimum range for fish performance. The UCM accumulates the sum of these effects in each channel unit, and multiplies by the area of the unit to predict the maximum number of parr the unit can hold under average environmental conditions. For spawning capacity, the starting habitat unit of interest is a patch of suitably sized gravel. The patch must be submerged to at least the body depth of the spawner, and have detectable velocities over the gravel. The number of spawners a patch can support is determined by area of the patch, with the area required per spawner increasing exponentially with the length of the spawning fish.

Passage Barriers

Past studies have established that the combination of jump pool depth and the height of the jump required determine if a small waterfall is passible by adult salmonids. Reiser and Peacock 1985 (cited in Newton and Brown 2004) determined that adult salmonids need a jump pool depth of ≥ 1.25 times the vertical height to be jumped. Accordingly, the project team used a stadia rod to measure the depth of the plunge pool below any potential barrier, and then measured the vertical height from the surface of the plunge pool to the water surface flowing over the barrier. The project team photographed an upstream view of the barrier, with a stadia rod in view to document the height of the barrier.

RESULTS

In this section of the report, the project team reports the values for habitat attributes that were measured during the March, 2015 survey, and compare them to measurements from the July, 2013 survey at the lower flow. The implication of differences and similarities found between the two surveys is addressed separately in the Discussion section of this report.

Flow During the Survey

Stream flow during the survey was determined by completing velocity measurements (USGS protocol) across each of the six cross sections where pressure transducers were installed for continuous depth monitoring (see Table 4). Calculated flows varied from 26.0 cfs to 44.4 cfs at the six sites, and averaged 33.6 cfs with a standard deviation of 7.10. Cross section views at each logger location can be found in Appendix D. Total discharge appeared to be constant during the survey, so the variation in estimated flow was likely caused by variation and the amount of flow passing through the substrate, and velocity measurement error due to the substantial channel roughness created by boulders dominating the substrate. The mean value of the flow measurements, 33.6 cfs, was used in all analyses that required a value of flow at the time of the survey.




Table 4. Calculated flows at each of the six cross sections where pressure transducers were installed and detailed measurements depth were completed at width increments of ≤ 3 feet.

Logger Channel unit Calculated flow (cfs)

1 1 37.72

2 8 31.73

3 22 44.44

4 50 26.32

5 38 35.39

6 32 26

Mean / SD 33.60 / 7.10

Flow-Based Changes in Habitat Attributes

Rearing Habitat Attributes

The project team compared measurements taken during the current survey at 34 cfs with those taken in the same sampling units during 2013 at 13 cfs. The mean of measurements from the three transects for each channel unit at 34 cfs was used in comparison to the mean for the single transect measured in each channel unit at 13 cfs. Results from the two flows were compared using Welch's paired t-test. Appendix 1 provides basic measurement comparisons between the two flow conditions.

Channel widths As expected, average wetted widths in both pools and riffles were significantly greater at 34 cfs than at 13 cfs (p < 0.05 for each; Figure 3). The width of pools increased 50% (3.5 m), while that of riffles increased 40% (3.1m). Data plotted in Figure 4 show, for example, wetted widths in units 6 and 32 showed little change, whereas widths in units 1, 2, and 11 changed dramatically.

In contrast to wetted widths, active channel widths of pools were not significantly different between the two flow conditions (p > 0.05), but active channel widths of riffles decreased significantly (p < 0.05) by 19% (2.5 m). Again, the plot of measurements for individual channel units shows that the magnitude of change varied substantially between units (Figure 5). In some cases, widths were substantially greater at flows of 34 cfs (unit 50) and in other cases, they were substantially less (units 6, 42, 49).




Figure 3. Box plots comparing active channel widths and average wetted widths in pools and riffles in units sampled at flows of 13 and 34 cfs. In both pools and riffles, average wetted widths were significantly higher under higher streamflow (both p < 0.05). Average active channel widths were not significantly for pools (p > 0.05), but riffle active channel width measurements were significantly lower at 34 cfs than at 13 cfs (p < 0.05). See Appendix B Table B-1.




Figure 4. Measured average wetted width at 13 cfs in 2013 and 34 cfs in 2015. Widths were measured in each unit at one transect in 2013 and three transects in 2015.




Figure 5. Active channel width measured at 13 cfs in 2013 and 34 cfs in 2015. Widths were measured in each unit at one transect in 2013 and three transects in 2015.

Channel depths No change in depth of pools or riffles (p > 0.05) was evident between 13 and 34 cfs (Figure 6). At both flows, pools averaged 1.3 m deep and riffles averaged 0.39 m deep. Similarly, there was no significant difference (p > 0.05) in active channel heights for pools between 13 cfs (2.0 m) and 34 cfs (1.7 m), but active channel height in riffles was significantly greater (p < 0.05) at 13 cfs (2.7m) than at 34 cfs (1.7).

Data plotted in Figure 7 show there is substantial variation between channel units in how much the depth changed. For example, Figure 7 shows maximum depth in pools was similar at the two flows in some pools (units 4, 11), greater at 13 cfs in some pools (units 16 and 38) and much less at 13 cfs in some pools (units 2 and 50). Figure 8 shows that riffle depths were greater at 13 cfs in units 1 and 6, but less at 13 cfs in units 8 and 32. Figure 9 shows that active channel height was greater at 13 cfs in most units, particularly in units 3, 4, and 6, but was also less in at 13 cfs in units 16 and 21.




Figure 6. Box plots comparing active channel height and maximum depth in pools and average depth in riffles in units sampled both at 13 cfs in 2013 and 34 cfs in 2015. Depths did not differ significantly for either pools or riffles between the two years (both p > 0.05). Pool active channel heights were not significantly different (p > 0.05) but riffles were significantly different (p =



Figure 7. Maximum pool depth measured at 13 cfs in 2013 and 34 cfs in 2015.




Figure 8. Riffle depth measured at 13 cfs in 2013 and 34 cfs in 2015. Depths were measured in each unit at one transect in 2013 and three transects in 2015.




Figure 9. Active channel heights measured at 13 cfs in 2013 and 34 cfs in 2015. Active channel heights were measured in each unit at one transect in 2013 and three transects in 2015.

Velocity Velocities were significantly higher (p < 0.05) in riffles at 34 cfs than at 13 cfs (Figure 10). Velocity was not recorded in pools in 2013 at the low flow, because it was close to zero in most pools. However, at 34 cfs there was detectable velocity in most pools, and it averaged about 0.15 m/s. As with other metrics, changes in velocity differed between individual riffles, but increased at 34 cfs in most (Figure 11). Unit 17 was an exception where velocity was higher at 13 cfs.




Figure 10. Box plots comparing velocities in pools and riffles in units sampled both at 13 cfs in 2013 and 34 cfs in 2015. Average velocities in riffles were significantly greater at 34 cfs than at 13 cfs (p < 0.05). No velocities were measured in pools at 13 cfs in 2013. See Appendix B Table B-4.




Figure 11. Velocities measured in riffles at 13 cfs in 2013 and 34 cfs in 2015. Pool velocity was not measured at 13 cfs, and thus is not shown on this figure. Velocities were measured in each unit at one transect in 2013 and three transects in 2015.

Substrate Classification The substrate composition in the sampled pools and riffles are compared between years in Figure 12 (see Table B-3 in Appendix B). Boulders dominate the substrate in all channel unit types, and boulders only move at high flows. Thus, it is not surprising that substrate composition changed little in the two years between surveys. Boulders average 35 to 45 % of substrate in pools and 75 to 85% of substrate in riffles. The only notable change in substrate was an increase in the proportion of gravel in pools from 16% in 2013 to 28% in 2015 (Figure 12).




Figure 12. Box plots comparing percentage of substrate types in pools and riffles sampled during the two survey years. There were no significant differences (p > 0.05) in any of the substrate categories.

Wood Complexity and Channel Gradient Data comparing wood complexity and channel gradient measures between the two survey years are shown in Table B-2 (Appendix B). Wood complexity was comparable between the two surveys. Gradients of each measured channel unit were similar between years.




Spawning Habitat Attributes

The project team compared measurements of spawnable gravel patches taken during the current survey at 34 cfs with those taken in the same sampling units during 2013 at 13 cfs. Substrate patches that had obvious lateral slope or particle sizes outside the preferred range for spawners were not measured. The distinctive attributes measured at patches with suitable gravel size and slope were depth, velocity and area. See Table C-1 in Appendix C for all measurements from 2015.

The difference in area, depth, and velocity between the measurements at 13 cfs (2013) and 34 cfs (2015) varied between individual patches. Both position within the channel unit and area of some gravel patches had changed between the two surveys, which were separated in time to two high-flow seasons. Two patches (units 8 and 49) had small increases in size, and the two patches that were largest in 2013 had decreased by more the half in 2015 (Figure 13). Unit 16 had two submerged gravel patches at 34 cfs, but only the patch that corresponded to the patch measured at 13 cfs is shown in Figure 13.

Figure 13. Measured areas of spawning gravel patches at 13 cfs in 2013 and 34 cfs in 2015.




Depth of all four measured patches increased at 34 cfs (2015) compared to 13 cfs (2013). The increase in depth ranged from 0.08 m to 0.30 m (Figure 14).

Figure 14. Measured depths of spawning gravel patches at 13 cfs in 2013 and 34 cfs in 2015.

Velocities were higher at 34 cfs for two gravel patches, but were lower for two others. Patch areas decreased in channel units 16 and 50 (Figure 15) where velocity had increased at 34 cfs.




Figure 15. Measured velocities of spawning gravel patches at 13 cfs in 2013 and 34 cfs in 2015.

Estimated Production Potential

Predicted vs. Observed Rearing Capacities

Habitat attributes measured in 2013 were used by Cramer and Ceder (2013) to estimate rearing capacity for Chinook Salmon and Steelhead Trout parr at 13 cfs (Table 5). Cramer and Ceder (2013) also used hydraulic geometry equations to predict, with 2013 data, how that rearing capacity would change as flow increased. In 2015 the project team obtained the actual measurements of channel attributes at 34 cfs, and the project team again used these observed habitat values to estimate rearing capacity for Chinook Salmon and Steelhead Trout parr at 34 cfs. As predicted, the rearing capacity estimated with channel measurements at 34 cfs in 2015 was greater than the rearing capacity estimated with channel measurements at 13 cfs in 2013. The expanded area in riffles at 34 cfs accounted for the gain in rearing capacity (Table 5). However, the gain in estimated capacity in 2015 was less than half of what had been predicted by Cramer and Ceder (2013) for a simulated flow 34 cfs, both for Chinook Salmon and Steelhead Trout (Table 5). The total rearing capacity estimated from observed and measured dimensions at 34 cfs for Chinook Salmon was 2,789 parr and for Steelhead was 3,190 parr.

The project team will review the implications of this outcome in the Discussion section of this report.




Table 5. Comparison of the parr rearing capacity for habitat measured at 13 cfs to those predicted and measured for 34 cfs. Predicted values are from modeling output of Cramer and Ceder (2013). All capacities were estimated with the Unit Characteristic Method (UCM).

Capacity @ 13 cfs Capacity @ 34 cfs

Species Habitat Type 2013 Measured Predicted In 2013

Measured In 2015

Chinook Salmon Pool 651 870 543

Chinook Salmon Riffle 1118 4793 2246

Steelhead and Resident Trout

Pool 460 613 385


Riffle 1401 5996 2805

Spawner Capacity

Attributes of the gravel patches measured to determine spawning suitability at 34 cfs are shown adjacent to the minimum criteria for depth, area, and velocity at spawning for each species of interest in Table 6. The basis for these criteria was reviewed in detail by Cramer and Ceder (2013). All patches met the minimum depth and area requirements for spawning of Steelhead Trout and Rainbow Trout, but only the second gravel patch in unit 38 had sufficient velocity to meet the criteria. Only the patch in unit 4 had sufficient depth and area for a single pair of Chinook Salmon to spawn. Unit 4 is just downstream of the proposed powerhouse/tailrace, and so would be unaffected by the project. Due to the depth that could not be safely accessed by wading, no velocity was recorded in that unit. One patch each in units 38 and 49 were close to minimum criteria for area and depth to support a single pair of Chinook Salmon, but both had velocities that were less than half of the minimum criteria. Further, the patches in unit 38 were not present there during the 2013 survey, which indicates they are likely to be easily mobilized.

Table 6. Measurements of spawning patches identified during field survey. These are compared to the minimum requirements for target species to identify their suitability for spawning at 34 cfs. Only one gravel patch was found in unit 16 in 2013 and no patches were found in unit 38 in 2013.

Measured Values Chinook Salmon

Requirements Steelhead Trout Requirements

Rainbow Trout Requirements

Unit No.

Mean Depth (cm)

Area (m2)

Mean Velocity

(m/s)

Min. Depth (cm)

Min. Area (m2)

Min. Velocity

(m/s)

Min. Depth (cm)

Min. Area (m2)

Min. Velocity

(m/s)

Min. Depth (cm)

Min. Area (m2)

Min. Velocity

(m/s)

4 120 33.8 N/A

30.5 20.7 0.30 15.2 4.0 0.30 7.6 2.0 0.30

8 29.0 11.6 0.07

16 59.3 2.68 0.0

16 23.3 16.5 0.09

38 22.0 20.3 0.14

38 30.3 9.44 0.45

49 37.3 19.4 0.03

50 59.3 9.33 0.26




Uncertainty in Measurements and Predictions

Predicted vs. Observed Channel Unit Dimensions

Channel unit width and depth data collected in 2015 were used to test the accuracy of predictions from the hydraulic models used in Cramer and Ceder (2013). For those channel units that were sampled in both 2013 and 2015, the project team compared dimensions observed in 2015 to the values that Cramer and Ceder (2013) predicted for the same units at a hypothetical flow of 34 cfs. Predicted widths for riffles were greater than measured widths at 34 cfs (Figure 16), shown by points falling above the black 1:1 line, while predicted widths for pools were close to measured values, with the exception of two pools where widths were under predicted. In the case of depths, values predicted for 34 cfs were greater than measured depths, shown by points being above the 1:1 line (Figure 17). On average, widths at 34 cfs were under predicted for pools by 1.7 m and over predicted by 2.3 m for riffles. Depths were over predicted on average 0.5 m for pools and 0.3 m for riffles.




Figure 16. Comparison of mean wetted width (m) measured for individual channel units in 2015 (Observed axis) versus widths that were predicted (Predicted axis) for 34 cfs based on the hydraulic geometry methods reported by Cramer and Ceder (2013). The black line is the 1:1 line where observed and predicted are equal.

Additionally, the project team applied the hydraulic models used by Cramer and Ceder (2013) to predict the expected changes in wetted width and height as flow increases at the six locations where detailed cross sections were measured (cross sections are plotted in Appendix D). The predicted widths were compared to the measured widths at corresponding elevation increments of 0.15 m above the water. Figure 18 shows there was a range of variability between observed and predicted values at these cross sections. Differences between predicted and observed, whether over prediction or under prediction, vary between channel units – consistent over prediction in some channel units, under prediction in others, and a mix of over and under prediction for others. Fits of predicted to observed dimensions for each cross section are plotted in Appendix E. Biases in predictions – the average differences between predicted and observed values – ranged from a three meter over prediction to a 2 meter under prediction with mean of 0.1 meter under prediction. Differences are seen between habitat types with pool widths being over predicted by 0.75 meters, on average, and riffle widths being under predicted by 0.5 meters, on average.




Figure 17. Comparison of depths (m) measured for individual channel units in 2015 (Observed axis) versus depths predicted (Predicted axis) for 34 cfs based on the hydraulic geometry methods reported by Cramer and Ceder (2013). The black line is the 1:1 line where observed and predicted are equal.




Figure 18. Comparison of measured channel widths (m) (Observed axis) to those that were predicted (Predicted axis) for the six cross section profiles. Predictions were based on the hydraulic geometry methods reported by Cramer and Ceder (2013). The black line is the 1:1 line where observed and predicted values are equal. Each red and blue line is a trajectory of a channel cross section.

Effect of Measuring Multiple Transects per Unit on Estimation of Rearing Capacity

The change from measuring one transect per channel unit during the 2013 survey to measuring three transects per unit in the 2015 survey provided an opportunity to evaluate how the additional measurements affected estimation on fish rearing capacities. The variability in widths and lengths between transects in the same channel unit (see Figures 4, 5, 7, 8) illustrates that fish rearing capacity estimates will be influenced by where that transects is located. Channel dimensions clearly vary over the length of a channel unit. The project team investigated the range of this effect by using 2015 survey data to calculate the rearing capacity with data from only one of the three transects at a time to represent the unit’s dimensions. The project team then calculated the averages of the largest and smallest carrying capacity estimates for pools and for riffles from the one-transect-at-a-time analysis (Table 7). The maximum and minimum estimates represented a range from 80% to 122% of the estimated mean from all three transects for the rearing capacity in pools, and from 68% to 126% of that mean in riffles. Table 7 highlights the range and variance of single transect measurements compared to the mean of three measurements, suggesting three measurements may better represent channel dimensions.




Table 7. Estimates of maximum and minimum rearing capacities calculated if only one transect were measured and the mean capacity estimated by averaging all three transects in each channel unit. The minimum uses all the worst case transects and the maximum uses all the best case transects. Chinook values pertain to either spring-run or fall-run.

Species Habitat Type Min Mean Max

Chinook Salmon Pool 433 543 660

Chinook Salmon Riffle 1,444 2246 2,841

Steelhead or Rainbow Trout

Pool 307 385 468

Steelhead or Rainbow Trout

Riffle 1805 2805 3551

The project team compared the statistical advantages between the 2013 survey strategy to measure every channel unit, but with only one transect per unit, and the 2015 strategy to measure 40% of channel units, but with three transects per unit. Each method has strengths and weaknesses that depend on the variability in channel dimensions between channel units versus that within each channel unit. To make the comparison, the project team calculated the coefficient of variation, which expresses the standard deviation as a percentage of the mean. Thus, a lower coefficient of variation is desirable because it results in a tighter confidence interval around the mean. The coefficients of variation (CV) shown in Table 8 indicate that the 2015 strategy provided more favorable treatment of variance for rearing capacities than did the 2013 strategy. By measuring multiple transects in a subsample of channel units the CV is reduced 14 percentage points for Chinook Salmon in pools, 16 percentage points for Steelhead Trout in pools, and 32 percentage points for Chinook Salmon and Steelhead Trout in riffles. This suggests that the project team obtained more precise rearing capacity estimates with three transects sampled in a portion of channel units than with one transect sampled in all channel units.

Table 8. Comparison of coefficients of variation for fish rearing capacities in pools and riffles, compared between the 2013 and 2015 surveys.

Species

Habitat Type

2013 Survey

2015 Survey

Chinook Salmon Pool 83% 69%

Chinook Salmon Riffle 56% 24%


Pool 86% 70%


Riffle 56% 24%




DISCUSSION

Flow-based Changes in Habitat

Rearing Habitat Attributes

The comparison of survey results between flows of 13 cfs and 34 cfs revealed substantial variation in channel dimensions and responses to increased flow, but most changes were in the direction expected. For example, wetted channel widths were significantly higher and velocities increased at 34 cfs compared with 13 cfs. Habitat variables such as substrate composition, wood complexity, and channel gradient remained relatively constant, as would be expected under a short timescale and in the absence of scouring flows.

The large increase in channel width (50% in pools and 40% in riffles) without a significant change in depth between 13 and 34 cfs was surprising. These changes could indicate that the additional two transects measured in each unit could be wider on average than the single representative transect the project team measured in 2013. Alternatively, it could reflect an increase gravel accumulation in the channel units during the last two winters of low runoff. The South Fork of Battle Creek is a high gradient stream (generally ≥ 5% gradient) in the project reach that has a high capacity to transport gravel and finer substrate right through the reach. Some of this small diameter substrate may have settled out in the project reach during the last two years of low runoff. The substrate composition showed an increase in the gravel component, and channel filling would cause the higher flow (34 cfs) to spread more laterally and causing little change vertically.

Active channel widths showed substantially more variability than expected, and likely reflect a combination of sampling error for this metric, and changes in the distinguishing marks of the active channel margin that developed over the two years between surveys. The active channel dimensions should remain relatively stationary over a two-year period. However, active channel width was significantly less in 2015 than in 2013 for both pools and riffles, and active channel height was also lower in riffles, but unchanged in pools. A portion of this change was likely due to the substantial differences in active channel width and height measured between transects even within the same channel unit (see Figures 5 and 9). Active channel width varied up to 17 m between transects within the same unit, but also differed little within other units. Active channel height varied over 1 m between transects within some units, but varied less than 0.2 m in several other units. Some of this variation was likely due to a change between years in the appearance of markings that were used to distinguish active channel height. Flows were extremely low over the winter and spring of 2015, so some water marks from 2015, which would have been at a lower, narrower level on the channel banks, may have been mistaken for the average high water mark. Bankfull measures were initially developed for alluvial rivers with broad floodplains. In confined valleys without a floodplain, they are widely recognized as subjective estimates, frequently with high levels of uncertainty and error (Johnson and Heil 1996; Modrick and Georgakakos 2014). The lack of consistent measurements for these metrics is likely due in part to the difficulty in assessing the average high-water line, particularly in




bedrock-dominated reaches of Battle Creek, where reliable indicators of the average high-water line (vegetation, evidence of scour, watermarks, etc.) are sparse (Williams 1978).

Spawning Habitat Attributes

Depths of spawning gravel patches that were measured at both flows were found to increase, as expected, from 13 cfs to 34 cfs. However, velocities only increased at spawning patches found in pools (Channel Units 16 and 50), while they decreased at spawning patches found in riffles (Channel Units 8 and 49). The two gravel patches that were largest in 2013 each decreased in area by more than half (see Figure 13). These two patches were found in the pools that had slightly higher velocities, which is consistent with the finding that much of the gravel present at these particular spots in 2013 was transported during the modest high-flow seasons of the last two years.

The position and size of gravel patches also changed between 2013 and 2015 in several channel units. Two channel units (units 6 and 43) that had gravel patches predicted to be suitable for a pair of Chinook Salmon spawning in 2013 had no gravel patches in 2015. Units 21, 32, and 34 that had small gravel patches predicted to be suitable for Steelhead Trout spawning at 20 cfs in 2013 had no patches present in 2015. Unit 38 had two patches suitable for Steelhead spawning in 2015, yet had no suitable spawning patches present in 2013. The high frequency of substantial changes in spawnable gravel patches between 2013 and 2015 indicate that gravel patches in this high-gradient channel are likely to be mobilized, even during low flow years. This finding is consistent with those from Northwest Hydraulic Consultants’ (2015) study of sediment transport that determined the threshold flows at which transport begins for fine gravel (4-8 mm) is 20 cfs, and for medium gravel (8-16 mm) is 80 cfs in the project reach. The observed and predicted mobilization of gravels in the project reach represent a substantial risk to survival of eggs deposited in these gravels.

Predicted vs. Observed Carrying Capacities

Measured Production Potential

The project team had determined from the 2013 habitat survey of the LLHP project reach below Angel Falls that spawning capacity was the most limiting factor for spring-run Chinook Salmon, while rearing capacity was the most limiting factor Steelhead Trout and Rainbow Trout. The proposed project is not expected to operate at seasonal low flows, and thus would not affect spawning flows for spring- or fall-run Chinook Salmon, nor the rearing capacity of either species. Cramer and Ceder (2013) determined that, due to the shallow depths and small area of gravel patches with suitable particle size and slope orientation, there would only be one patch (in the survey area, but below the powerhouse/tailrace) with room for one Chinook Salmon redd at the median flows of 8-9 cfs during peak spawning in September-October and even lower minimum flows in many years might negatively impact this. Even at the 34 cfs flow surveyed in 2015, there were only two gravel patches within the project reach found to have area and depth approaching the minimum criteria for one pair of Chinook Salmon each, but velocities were less than half of the minimum criteria. At 13 cfs in 2013, which was a flow closer to what Chinook Salmon would have available at their time of spawning, average




velocities over the gravel patches at pool tailouts were all under 0.1 m/s (see Figure 14 in Sellheim and Cramer 2013). This is far below the velocity of 0.3 to 0.7 m/s where Chinook Salmon spawn (Keeley and Slaney 1996). Although Cramer and Ceder (2013) pointed out that greater flows could provide the velocities that Chinook Salmon prefer, our findings in 2015 show that suitable velocities are generally not present over large gravel patches even at a flow of 34 cfs. These findings apply equally to spring-run and fall-run Chinook, because both would spawn in the late summer to early fall when median flows are only 8-9 cfs and recorded as much less than that in many years (3 cfs in several recent years and even down to no flow in Fall 2014).

The occurrence of gravel patches in low velocity areas is consistent with the high gradient of the project reach, in which gravels are only likely to settle out in protected areas. Even in those protected areas, higher flow that overtop obstructions protecting gravel patches are then likely to create downward velocities that scour and transport the gravel. In this process, new gravel would be deposited in such areas as the flows decrease, because the obstructions would again create zones of lower velocity. Such a process of scour and re-depositing of gravel is likely to occur frequently across years during the high flow season, making these gravel patches a risky location for salmon and trout to deposit eggs.

The number of suitable patches for Steelhead Trout spawning was substantially greater than that for Chinook Salmon, because body depth, and therefore spawning depth, of Steelhead Trout is half of that for Chinook Salmon (15 cm vs. 30 cm), and the area defended per spawning pair is only 4 m2 for Steelhead Trout, one fifth of the 20.7 m2 required per pair of Chinook Salmon. The spawning area defended by a pair of rainbow trout is even smaller, at 2.0 m2, and the depth is shallower at 7.6 cm, so all gravel patches met area and depth criteria for resident trout. In 2015 at 34 cfs, only one of the gravel patches identified was too small for Steelhead spawning, and all had sufficient depth. Cramer and Ceder (2013) found there were good spawning opportunities for Steelhead Trout even at flows down to 10 cfs. They predicted that spawning capacity would increase by 18% if flows increased from 10 to 20 cfs, but would change little if flows doubled again to 40 cfs. The project team findings in 2015 did not refute this prediction, although fewer patches of gravel were found in the units surveyed than in 2013. Again, this highlights the mobile nature of these gravel patches in a high gradient reach. Further, the comparison between 2013 and 2015 indicates that the changing size and number of gravel patches between years may have greater influence on spawning capacity than does flow.

Cramer and Ceder (2013) expressed spawning capacity in terms of the potential number of age-1 parr that could be produced, so it was possible to directly compare carrying capacities for spawning and rearing to determine which was likely to be the bottleneck to production. Recall that rearing capacity in any given stream is generally determined by the lowest flow during the growing season (Berger and Greswell 2009), and spawning capacity is limited by the flow at the time of spawning. Rearing capacity for spring- and fall-run Chinook Salmon, as well as for Steelhead and Rainbow Trout is limited by the same low flow season (late summer to early fall), but Chinook Salmon spawning would occur during low flows in the fall while Steelhead Trout and Rainbow Trout spawning would occur during high flows in the winter and spring.




The habitat conditions found in 2015 at 34 cfs again confirm the findings of Cramer and Ceder (2013) that spawning capacity was the most limiting factor for Chinook Salmon, while rearing capacity was the most limiting factor Steelhead and Rainbow Trout. For Chinook Salmon, the one redd capacity would produce an estimated 218 parr for spring run, which is only 17% of the reach rearing capacity of 1,298 parr at a simulated low flow of 10 cfs. At 34 cfs in 2015, the estimated parr capacity for Chinook Salmon increased only to 2,789 parr, which was still far more rearing potential than the spawning capacity could fully seed. In contrast to Chinook Salmon, spawning capacity for Steelhead Trout at only 10 cfs can produce roughly 10 times more parr (13,092 parr) than the typical low-flow rearing capacity (1,407 parr) can support (Cramer and Ceder 2013). At 34 cfs, the capacity for Steelhead Trout and Rainbow Trout rearing increased only to 3,190 parr, which is still far less than 13,092 parr that could be produced by spawning capacity, even at only 10 cfs, as estimated by Cramer and Ceder (2013).

Comparison of Measured and Predicted Production Potential

Rearing capacity estimates based on actual channel measurements at 34 cfs in 2015 were less than half of the capacity that was predicted at that flow, based on the hydraulic geometry equations used by Cramer and Ceder (2013). This over prediction of the change in rearing capacity was due to the channel dimensions responding differently to the increase in flow than was predicted. Wetted widths increased by 40-50%, but depth did not increase.

Width and depth are both important variables in determining rearing capacity in the UCM. The UCM estimates carrying capacity as a function of surface area times parr density. So, as the width of a channel unit changes, the surface area changes, and that translates to a change in rearing capacity. If width changes by 20%, then area and capacity change by 20%. Depth, on the other hand, affects parr density, because salmon and trout parr have strong preferences for the range of depth they will use. Due to the strength of this preference, a small change in depth can result in a large increase in fish density. So, at depths between 0.2 and 0.8 m, the scalar (multiplier) for fish density increases over six fold (Figure 19). Thus, changes in depth, particularly in riffles because of their shallow nature, tend to have a stronger influence on rearing capacity than do changes in width.




Figure 19. Values of the depth scalar by which parr densities are multiplied in the UCM to estimate parr capacity of a stream channel unit.

As a result of the lesser change in depth than was predicted for 34 cfs, the estimated capacity at 34 cfs was only 49% of what was predicted for Chinook Salmon and 48% of what was predicted for Steelhead Trout. Still, the rearing capacity estimated from channel dimensions measured at 34 cfs in 2015 increased over the rearing capacity estimated from channel dimensions measured at 13 cfs in 2013. Thus, rearing capacity responds to increases in flow at a lesser rate than had been predicted by Cramer and Ceder (2013).

Predicted vs. observed channel unit dimensions

Including hydraulic geometry models in the UCM model was designed to provide a method to quickly assess changes in rearing capacity and spawning production under different flow regimes using commonly collected habitat data. While simplifying assumptions (e.g. channel cross-sectional shape) must be made, the intended value of this approach was that it should produce good approximations of changes in the wetted channel dimensions as flow increases. Validating the hydraulic geometry models with the 2015 data provides an opportunity to determine the presence and effects of any systematic biases.

Comparisons of observed widths and depths from 2015 to hydraulic geometry model predictions from the 2013 analysis show tendency to over predict changes in depth in both pools and riffles, and to over predict changes in riffles for the change in flow from 13 to 34 cfs. Consistent trends in deviations of predictions from measured values suggest that the models used by Cramer and Ceder (2013) do not fully capture the wetted channel shape for the low flow levels studied. The hydraulic models are simple and rely on smooth, consistent channel cross sections for accurate predictions. Battle Creek has a boulder-dominated channel with channel cross sections that are neither smooth nor consistent (see transect profiles in Appendix D). Within any channel unit the predictions can diverge greatly from measured values in




individual channel units (Figure 19). This is caused partially by the channel shape, but may also be related to the difficulty in precise calls on active channel heights, widths, and flows, which are inputs to the hydraulic geometry models, and may lead to consistent biases. However, when biases are consistent, it may be possible to calibrate the hydraulic model outputs by adjusting coefficients, or by measuring additional increments of channel width and height for the low flow channel. However, such calibration is beyond the scope of the survey described here.

Measurement and Prediction Uncertainty

Sampling in 2013 was designed to sample each channel unit with one transect so rearing capacities could be calculated for each channel unit in the reach. This extensive sample ensured that all habitat types and channel units were sampled allowing inference across all habitat types and the reach as a whole. The main limitation of this strategy is that measurements along a single transect may not accurately represent average habitat conditions in the channel unit. With only one transect, the variation in dimensions within channel units cannot be estimated. The measurements from three transects per channel unit during the 2015 survey provides estimates of width and depth variation within a unit, and offers a basis to compare which strategy (2013 vs. 2015) offers the best approach to deal with variation in channel attributes.

The larger coefficients of variation in 2013 were a result of not accounting for within-channel unit variation. The reduced coefficients of variation achieved in 2015 should provide more accurate estimate of rearing capacity. It should be recognized that the 2015 sampling was limited to pools and riffles, so some error in expansion to the full project reach will accrue when estimates are expanded to account for any production potential rapids and cascades.

EXISTING FISH PASSAGE IMPEDIMENTS

Measurement Results

The project team measured dimensions of seven potential barriers to adult passage that were located at the upstream or downstream terminus of the channel units the project team surveyed in March, 2015. Passage barrier measurements are summarized in Table 9, and example photographs showing the jump height with a stadia rod are in Appendix A (Photos A-7-8, A-11-15). All barrier assessment was based on whether the jump pool was > 1.25 times greater than the vertical height from the pool water surface to the top of the barrier.

Only one of the seven potential barriers measured during the field survey exceeded the 1.25 ratio of depth to jump height, and therefore is considered passable. Two others were shallower than desirable, but the jump height was near 1 m and might be achievable for Steelhead Trout if they could get the right approach to achieve sufficient vertical velocity. The remaining four appeared to be impassable at 34 cfs streamflow conditions. The barrier showing the greatest divergence from being passable was the location that has been referred to as either 8-foot falls or Powerhouse Falls at the head of channel unit 4, just downstream




from the proposed powerhouse/tailrace location. From now on, it will be referred to as Powerhouse Falls. A photo of the barrier is shown in Appendix A (Photo A-13). If Chinook Salmon or Steelhead Trout could reach this falls, it would likely prevent their passage into the project area at a wide range of flows.

Table 9. Measured values of passage barriers along Battle Creek. Barriers with a ratio of less than 1.25 for jump pool depth to the jump height are likely to be impassable, based on the work of Powers and Orsborn (1985). This ratio may not be as limiting at jump heights of 1 m or less if Steelhead Trout can achieve sufficient vertical velocity.

Channel Unit Barrier Type

Depth (m) Height (jump) (m) Depth/Height

Ratio Potential barrier?

1 Vertical 0.7 0.8 0.88 Uncertain

4 Vertical 0.5 2.3 0.22 Yes

38 Vertical 1 1.7 0.59 Yes

38 Vertical 0.75 2 0.38 Yes

45 Vertical 1 1.1 0.91 Uncertain

49 Vertical 1 2 0.50 Yes

50 Vertical 1.3 1 1.3 No

Discussion

Our measurements of plunge pool depths and jumps heights at potential small falls within the project reach indicate there are several locations that will prevent upstream passage at low to moderate flows. The most significant of these potential passage barriers was Powerhouse Falls, found at channel unit 4, just below the proposed powerhouse/tailrace location. At the flow of 34 cfs, the required

Date post:	15-Aug-2020
Category:	Documents
Upload:	others
View:	0 times
Download:	0 times

LASSEN LODGE HYDROELECTRIC PROJECT - Battle Creek… · 07/07/2015 · Spawner Capacity ... Map of...

Documents