GRAVEL 2016 ANNUAL REPORT

Transcription

1 SETTLEMENT AGREEMENT ARTICLE 108 GRAVEL 2016 ANNUAL REPORT REPORTING PERIOD JANUARY 1 DECEMBER 31, 2016 BAKER RIVER HYDROELECTRIC PROJECT FERC No November 2017 BAK SA 108 Annual Report 2016.Docx 14 Nov ember 2017 Baker Riv er Hy droelectric Project

2 Gravel 2016 Annual Report CONTENTS CONTENTS 1.0 Executive Summary Introduction Activity Report Gravel Monitoring References... 6 APPENDIX A: BAKER RIVER GRAVEL MONITORING REPORT... 7 List of Figures Figure 1. Process flow chart for implementation of SA 108, Gravel, for the Baker River Hydroelectric Project Figure 2. A map of the plan area of the Baker Gravel Implementation Plan, showing the general location of the transects, Wolman pebble counts, and subsurface sampling... 5 List of Tables Table 1. Summary of the site-averaged bankfull depths (in feet) for the cross-sections at Sites A, B, and C Table 2. Summary of gravel monitoring results at Sites A, B, and C on the Skagit River, BAK SA 108 Annual Report 2016.Docx 14 Nov ember 2017 Baker Riv er Hy droelectric Project Page ii

3 1.0 Executive Summary This gravel annual report reviews activities undertaken by Puget Sound Energy (PSE) in 2016 for implementation of settlement agreement article 108 (SA 108), Gravel, of the Baker River Hydroelectric Project license. The report covers the SA 108 reporting period of January 1 through December 31, 2016 as outlined in the revised aquatics reporting schedule submitted to the Federal Energy Regulatory Commission (FERC) on September 11, 2014, and approved by the FERC on January 16, In 2016, PSE s efforts for SA 108 included continued gravel monitoring in the Skagit River, as required by the Baker River Gravel Management Plan (the Management Plan) and the Baker River Gravel Implementation Plan (the Implementation Plan). 2.0 Introduction This gravel annual report has been prepared for the Baker River Hydroelectric Project pursuant to the Order on Offer of Settlement, Issuing New License and Dismissing Amendment Application as Moot (the license) issued by the Federal Energy Regulatory Commission (FERC) on October 17, In appendix A of the license, SA 108 sets forth the applicable requirements for the Management Plan, which in turn sets forth the requirements for this annual report. This annual report summarizes the activities conducted under SA 108 in 2016, including management activities, monitoring, design and planning, acquisition-related activities, consultation, documents prepared, modifications to or deviations from planned activities, issues and resolution, accounting, and proposed changes to the FERCapproved plan. It has been prepared in consistence with SA 102 and SA Activity Report Principal activities in 2016 included continued Skagit River gravel monitoring as required by the Management Plan and described in the Implementation Plan. The Management Plan provides for the monitoring of conditions in the Skagit River below the Baker River confluence, and implementation of gravel augmentation measures if monitoring results indicate that such actions are warranted. Gravel augmentation will be implemented using best management practices and according to guidelines identified through the permitting process and consultation with the ARG. Changes to the standards and criteria will be reported in the annual report in accordance with SA 102. The monitoring documents conditions for the parameters that determine whether gravel augmentation is warranted. Monitoring results are reported to the ARG annually, along with a specific description of the status of conditions identified as gravel augmentation triggers. If warranted, gravel augmentation will consist of annually placing up to 12,500 tons of coarse sediment in the lower Baker River alluvial fan to allow subsequent downstream redistribution by the river during high flows. If gravel augmentation triggers are not exceeded, monitoring will continue according to the timeline identified in the implementation plan (figure 1). BAK SA 108 Annual Report 2016.Docx 14 Nov ember 2017 Baker Riv er Hy droelectric Project Page 1

4 Gravel 2016 Annual Report Activity Report Submit BRGMP to FERC FERC Approval Implementation Plan Identify Potential Augmentation Measures Develop Monitoring Procedures Identify Augmentation Triggers Monitoring No Does Monitoring Show Trend of Reduced Gravel Recruitment? Yes No Gravel Augmentation Warranted? Yes Develop Gravel Augmentation Proposal Review and Approval Permitting Implement Gravel Augmentation Figure 1. Process flow chart for implementation of SA 108, Gravel, for the Baker River Hydroelectric Project. BAK SA 108 Annual Report 2016.Docx 14 Nov ember 2017 Baker Riv er Hy droelectric Project Page 2

5 Gravel 2016 Annual Report Activity Report 3.1 Gravel Monitoring The Implementation Plan describes monitoring procedures, conditions that will trigger augmentation, and identifies potential augmentation measures. Monitoring includes measuring river bed profiles to assess channel response, and recording multiple Wolman pebble counts and subsurface sediment sampling to assess substrate response. Monitoring of river bed profiles and Wolman pebble count surveys was initiated in 2012 and is conducted annually. Subsurface sampling was conducted in 2013 and 2015; it will be conducted again in 2017, and thereafter at 10-year intervals. The results from monitoring in 2016 are summarized below, and the complete monitoring results and analysis are presented in the report Baker River Gravel Implementation Plan Monitoring Results Years 2012 through 2016 in appendix A. Monitoring Results Summary Baseline gravel monitoring began in 2012 (PSE, 2013). Three monitoring sites were established in 2012 on the Skagit River (figure 2): 1. Site A Upstream of the Baker River confluence but below the Sauk River confluence near the inflection point between two bends (RM 61). 2. Site B In bar habitat downstream of the Baker River confluence, and upstream and around the channel bend from the U.S. Geological Survey gage (RM 55). 3. Site C Upstream from the Finney Creek confluence near Piscatore Lane (RM 51.5). Three cross-sections were surveyed annually at each site from 2012 to The results from 2016 were similar to those of previous years, with site averaged bankfull depths of 21.4 feet, 20.6 feet, and 21.1 feet at Sites A, B, and C, respectively (table 1). Table 1. Summary of the site-averaged bankfull depths (in feet) for the cross-sections at Sites A, B, and C. Site Year A B C Ten Wolman pebble count surveys (n=1,000) were performed annually at each site from 2012 to Wolman pebble count results for 2016 showed an increase in fine sediments and small grains at all sites. The percentages of substrate greater than 6 inches were 0.7%, 1.0%, and 0.9%, at Sites A, B, and C, respectively. Median grain sizes from the surface sediments (pebble counts) collected in 2016 were 42, 47, and 45 at Sites A, B, and C, respectively (table 2). An assessment of sample size was performed to determine whether the number of pebble counts could be reduced while still obtaining a reliable estimate of percent greater than 6 inches in size. Each site was examined to evaluate sample size in relation to incremental changes in confidence intervals or particle size percentiles. The results suggested that the sample size might be reduced from 1,000 to 500. However, the objective of the study is to detect an absolute change in percent substrate greater than 6 BAK SA 108 Annual Report 2016.Docx 14 Nov ember 2017 Baker Riv er Hy droelectric Project Page 3

6 Gravel 2016 Annual Report Activity Report inches over 10 years using linear regression trend analysis. Therefore, we need information on the variance within years and variance among years. Further analyses suggests that the sample size of pebble counts (i.e., ten transects per site and 100 pebble counts per transect (n=1,000) for each of three sites) could be reduced to 20 counts per transect (n=200) while maintaining the necessary rigor to quantify trends. However, since the armor ratio depends on analyses of both surface and subsurface substrates, and two years of subsurface data are available as of fall 2016, any proposal to reduce the surface substrate sample size will be deferred until at least three years of subsurface substrate data are available. Ten subsurface samples were collected from each site in 2013 and These samples were wet-sieved onsite, and the volume retained on each sieve size was determined through volumetric displacement. These volumes were adjusted to account for the dry portion of each wet sediment volume. Grain size distributions from these samples were analyzed to determine a median grain size from the ten samples collected at each site. The median grain size of the surface sediment (determined from pebble counts) was divided by the median grain size of the subsurface sediment to determine an armor ratio. In 2013, the armor ratios were 1.7, 2.6, and 2.5 at Sites A, B, and C, respectively. In 2015, the armor ratios were 2.5, 2.4, and 1.9 at Sites A, B, and C, respectively. Note that these analyses are not updated for 2016, as no subsurface samples were planned or taken in These analyses and results will be updated after the 2017 field effort, when subsurface samples are scheduled to occur. An armor layer ratio greater than 3 was identified as a trigger to indicate the potential need for gravel augmentation. The statistical probability of detecting an increase of 10% in the percentage of sediment particles greater than 6.0 inches after 10 years was evaluated based on the first 3 years of substrate data. The variance of the linear regression slope for each site was estimated using the mean squared error (MSE) from a one-way analysis of variance with year as the main effect, divided by the sum of squared deviations in a sequence of ten years (Zar, 1996). This variance estimate includes variability within and among years. The minimum detectable difference for the slope is the change per year, which in this case is 1%. A simulation was conducted to estimate the effects of reducing sample size on this statistical power to detect trends. The simulated scenarios were formed by reducing the number of samples per transect from 100 to 50 or 20. For 50 samples per transect, every second transect was selected from the data for each site, and the power computed as before. Because there were two ways to select these transects for each site (e.g., even or odd numbered points), both estimates were made, and the highest MSE estimate was used as a conservative estimate. For 20 samples per transect; only every fifth point along each transect was included in the sample, resulting in five possible samples and five MSE estimates from which the highest was used. The statistical power for detecting trends, the precision and bias of the proportion estimate, and the precision of the median substrate size were evaluated for the total and reduced simulated scenarios. The statistical power analysis showed that trends of 1% per year would be easily detectable with sample sizes reduced to as few as 20 samples on each of 10 transects. BAK SA 108 Annual Report 2016.Docx 14 Nov ember 2017 Baker Riv er Hy droelectric Project Page 4

7 Gravel 2016 Annual Report Activity Report However, this would result in some loss in accuracy and precision when estimating the proportion of substrate greater than 6 inches in diameter. The armor ratio depends upon both the results from the pebble count surveys and the results from subsurface samples. The effects that reducing the sample size of pebble counts or reducing the number of subsurface samples would have on the armor ratio will be evaluated after By that time, there will be three years of armor ratio results to analyze. A recommendation on appropriate sample sizes for future monitoring efforts will be made based on the results of these analyses. Figure 2. A map of the plan area of the Baker Gravel Implementation Plan, showing the general location of the transects, Wolman pebble counts, and subsurface sampling. Table 2. Summary of gravel monitoring results at Sites A, B, and C on the Skagit River, Monitoring Metric Site A Site-averaged bankfull depth (feet) B C Percentage of surface sediment greater than 6 inches Median grain size of surface sediment (mm) Median grain size of subsurface sediment (mm) Armor ratio A B C A B C A n/a 31 n/a 24 n/a B n/a 25 n/a 24 n/a C n/a 25 n/a 25 n/a A n/a 1.7 n/a 2.5 n/a B n/a 2.6 n/a 2.4 n/a C n/a 2.5 n/a 1.9 n/a BAK SA 108 Annual Report 2016.Docx 14 Nov ember 2017 Baker Riv er Hy droelectric Project Page 5

8 Gravel 2016 Annual Report References 4.0 References PSE (Puget Sound Energy, Inc.) Baker River Gravel Implementation Plan Baseline Monitoring Year Puget Sound Energy, Bellevue, Washington. Zar, Jerrold, H Biostatistical Analysis. Third Edition. Prentice Hall, Upper Saddle River, New Jersey. BAK SA 108 Annual Report 2016.Docx 14 Nov ember 2017 Baker Riv er Hy droelectric Project Page 6

9 APPENDIX A: BAKER RIVER GRAVEL MONITORING REPORT BAK SA 108 Annual Report 2016.Docx 14 Nov ember 2017 Baker Riv er Hy droelectric Project Page 7

10 Baker River Gravel Implementation Plan Monitoring Results Years 2012 through 2016 Settlement Agreement Article 108 BAKER RIVER PROJECT, FERC No Puget Sound Energy Bellevue, Washington Draft 1 February 2017

11 Baker River Gravel Implementation Plan Monitoring Results Years 2012 through 2016 Settlement Agreement Article 108 BAKER RIVER PROJECT FERC No Puget Sound Energy N.E. 4th Street Bellevue, Washington Draft 1 February 2017

12 Contents CONTENTS List of Figures... iv List of Tables... v Acronyms and Abbreviations... vi 1.0 Executive Summary Introduction Background Geomorphic Equilibrium Skagit River Geomorphic Process Conditions Future Skagit River Geomorphic Process Conditions Distribution of Spawning Salmonids in the Skagit River Monitoring Procedures Monitoring Objective Area Monitoring Procedures Timing and Frequency Augmentation Trigger Channel Response Surficial Substrate Response Subsurface Substrate Response Monitoring Results Cross-Section Profiles Wolman Pebble s Armor Ratio Summary References APPENDIX A: APPENDIX B: APPENDIX C: CHANNEL CROSS-SECTION 2016 SURVEY RESULTS WOLMAN PEBBLE COUNT 2016 SURVEY RESULTS SUBSURFACE SAMPLING 2015 SURVEY RESULTS BakerGravel_SA108_2016MonitoringResults_ docx Page iii Draft 1 February 2017

13 Contents List of Figures Figure 1. Site-averaged bankfull depth in 2012, 2013, 2014, 2015, and 2016 at Sites A, B, and C on the Skagit River Figure 2. Percentage of surface sediment greater than 6 inches in size in 2012, 2013, 2014, 2015 and 2016 at Sites A, B, and C on the Skagit River... 3 Figure 3. Armor ratio in 2013 and 2015 at Sites A, B, and C on the Skagit River. (Next analysis to be conducted in 2017)... 4 Figure 4. Process flow chart for implementation of SA 108 Gravel for the Baker River Hydroelectric Project Figure 5. Schematic of middle Skagit River hydrography, river miles and bedload transport drainage areas Figure 6. Plan area of the Baker Gravel Implementation Plan showing general transect, Wolman pebble count, and subsurface sampling locations Figure 7. Example alignment of Wolman pebble count transects on a Skagit River gravel bar Figure 8. Example of bankfull depth calculation of a cross-section of the Skagit River Figure 9. Example of trend analysis of bankfull depth from a monitoring site on the Skagit River over a 10-year period Figure 10. Example of percent coarse substrate calculation from Wolman pebble count grain size distribution Figure 11. Example of trend analysis of percent coarse substrate from a gravel bar on the Skagit River over a 10-year period. 20 Figure 12. Locations of cross-section transects and pebble count surveys in Skagit River downstream from Sauk River Confluence and upstream from Baker River Confluence, Site A Figure 13. Locations of cross-section transects and pebble count surveys in Skagit River downstream from Baker River Confluence and upstream from USGS Gage No (Skagit River near Concrete), Site B Figure 14. Locations of cross-section transects and pebble count surveys in Skagit River at Piscatore Lane, Site C Figure 15. Surveyed cross-section profiles at Transect TRA1, Site A on Skagit River, 2012 through Profile Looking Downstream Figure 16. Surveyed cross-section profiles at Transect TRA2, Site A on Skagit River, 2012 through Figure 17. Surveyed cross-section profiles at Transect TRA3, Site A on Skagit River, 2012 through Figure 18. Surveyed cross-section profiles at Transect TRB1, Site B on Skagit River, 2012 through Figure 19. Surveyed cross-section profiles at Transect TRB2, Site B on Skagit River, 2012 through Figure 20. Surveyed cross-section profiles at Transect TRB3, Site B on Skagit River, 2012 through Figure 21. Surveyed cross-section profiles at Transect TRC1, Site C on Skagit River, 2012 through Figure 22. Surveyed cross-section profiles at Transect TRC2, Site C on Skagit River, 2012 through Figure 23. Surveyed cross-section profiles at Transect TRC3, Site C on Skagit River, 2012 through Figure 24. Results of pebble count surveys conducted at Site A on the Skagit River from 2012 through Figure 25. Results of pebble count surveys conducted at Site B on the Skagit River from 2012 through Figure 26. Results of pebble count surveys conducted at Site C on the Skagit River from 2012 through Figure 27. Volumetric correction factor used to determine the dry portion of a wet sediment sample Figure 28. Grain size distributions of surface and subsurface samples collected from Site A on the Skagit River in Figure 29. Grain size distributions of surface and subsurface samples collected from Site B on the Skagit River in Figure 30. Grain size distributions of surface and subsurface samples collected from Site C on the Skagit River in BakerGravel_SA108_2016MonitoringResults_ docx Page iv Draft 1 February 2017

14 Contents List of Tables Table 1. Estimated standard error of slopes and statistical power to detect a 10% increase over 10 years with annual sampling in percent of sediment particles greater than 6.0 inches based on observed variance Table 2. Comparison of various measures of statistical power among several reduced pebble count sample size scenarios Table 3. Summary of gravel monitoring results at Sites A, B, and C on the Skagit River from 2012 through 2016, and schedule for interpretation of results BakerGravel_SA108_2016MonitoringResults_ docx Page v Draft 1 February 2017

15 Acronyms and Abbreviations Acronyms and Abbreviations This abbreviation, acronym, or short name ARG BRGIP BRGMP D50 FERC GIS GPS MSE NAVD 88 PSE RM SA USGS WDFW Refers to Aquatic Resource Group Baker River Gravel Implementation Plan Baker River Gravel Management Plan Median particle size, half of the sediment particles are larger and half of the sediments particles are smaller than this size Federal Energy Regulatory Commission Geographic Information System Global Positioning System Mean Squared Error North American Vertical Datum. Unless specifically noted, all elevations refer to the GISbased datum of Puget Sound Energy, Inc. River Mile Settlement Agreement United States Geological Survey Washington State Department of Fish and Wildlife BakerGravel_SA108_2016MonitoringResults_ docx Page vi Draft 1 February 2017

16 Executive Summary 1.0 Executive Summary Operation of Puget Sound Energy s (PSE) Baker River Hydroelectric Project Federal Energy Regulatory Commission (FERC) No. P-2150, ( Baker Project ) interrupts the downstream movement of gravels and cobbles in the lower Baker River. On January 19, 2011, PSE filed the Baker River Gravel Management Plan (PSE 2011) outlining the process to implement settlement agreement article 108 (SA 108), Gravel of the Order on Offer of Settlement, Issuing New License and Dismissing Amendment Application as Moot for the Baker River Hydroelectric Project (FERC No. P-2150). The Baker River Gravel Management Plan established guidelines and procedures to evaluate and monitor channel and substrate conditions of the lower Baker River alluvial fan and affected reaches of the Skagit River downstream and immediately upstream of the Baker River confluence, and to implement gravel augmentation measures if warranted. On March 2, 2011, the Federal Energy Regulatory Commission approved the management plan and required that an implementation plan be developed within one year. The Baker River Gravel Implementation Plan (BRGIP) (PSE 2012) describes monitoring procedures, conditions that will trigger augmentation, and identifies potential augmentation measures. Monitoring includes measuring river bed profiles to assess channel response, and recording multiple Wolman pebble counts and subsurface sediment sampling to assess substrate response. Monitoring of river bed profiles and surficial Wolman pebble count surveys has been performed in 2012, 2013, 2014, 2015 and 2016, and will continue to be conducted annually. Subsurface sampling was performed in 2013 and 2015, and will be conducted in 2017, and then at 10-year intervals. Baseline monitoring was conducted in 2012 (PSE 2013). Three monitoring sites were established in 2012 on the Skagit River: 1. Site A Upstream of Baker River confluence but below Sauk River confluence near the inflection point between two bends (RM 61). 2. Site B Downstream of Baker River confluence in bar habitat upstream and around the channel bend from the U.S. Geological Survey (USGS) gage (RM 55). 3. Site C Upstream from Finney Creek confluence near Piscatore Lane (RM 51.5). Three cross-sections were surveyed at each site in 2012, 2013, 2014, 2015, and Results of these surveys are shown in figure 1. In 2012, site-averaged bankfull depths were 21.6 ft, 20.7 ft, and 21.0 ft at Sites A, B, and C, respectively. In 2013, site averaged bankfull depths were 21.6 ft, 20.7 ft, and 21.2 ft at the same three sites. In 2014, site averaged bankfull depths were 21.5 ft, 20.6 ft, and 21.1 ft at Sites A, B, and C, respectively. In 2015, site averaged bankfull depths were found to be 22.0 ft, 20.6 ft, and 21.5, respectively. During the most recent survey effort in 2016, site averaged bankfull depths were determined to be 21.4 ft, 20.6 ft, and 21.1 ft at Sites A, B, and C, respectively. Results for site-averaged bankfull depths are shown in figure 1. BakerGravel_SA108_2016MonitoringResults_ docx Page 1 Draft 1 February 2017

17 Executive Summary Figure 1. Site-averaged bankfull depth in 2012, 2013, 2014, 2015, and 2016 at Sites A, B, and C on the Skagit River. Ten Wolman pebble count surveys (n=1,000) were performed at each site in 2012, 2013, 2014, 2015 and From these surveys, the percentage of surface sediment greater than 6 inches was determined, and the results of these analyses are shown in figure 2. In 2012, the percentage of substrate greater than 6 inches was 2.3%, 1.4%, and 1.7% at Sites A, B, and C, respectively. In 2013 the percentage greater than 6 inches was 0.8%, 2.6%, and 1.4% at the same three sites. In 2014, the percentage of substrate greater than 6 inches was 1.3%, 3.0%, and 2.3% at Sites A, B, and C, respectively. In 2015, the percentage of substrate greater than 6 inches was 3.1%, 2.8%, and 1.5%, at Sites A, B, and C, respectively. During the most recent survey effort in 2016, the percentage of substrate greater than 6 inches was found to be 0.7%, 1.0%, and 0.9%, at Sites A, B, and C, respectively. Results for the percentage of surface sediment greater than 6 inches are shown in figure 2. BakerGravel_SA108_2016MonitoringResults_ docx Page 2 Draft 1 February 2017

18 Executive Summary Figure 2. Percentage of surface sediment greater than 6 inches in size in 2012, 2013, 2014, 2015 and 2016 at Sites A, B, and C on the Skagit River. Ten subsurface samples were collected from each site in 2013 and These samples were wet-sieved on site, and the volume retained on each sieve size was determined through volumetric displacement. These volumes were adjusted to account for the dry portion of each wet sediment volume. Grain size distributions from these samples were analyzed to determine a median grain size from the ten samples collected at each site. The median grain size of the surface sediment (determined from pebble counts) was divided by the median grain size of the subsurface sediment to determine an armor ratio. Results of these analyses are shown in figure 3. In 2013, the armor ratios were found to be 1.7, 2.6, and 2.5 at Sites A, B, and C, respectively. During the most recent sampling effort in 2015, the armor ratios were found to be 2.5, 2.4, and 1.9 at Sites A, B, and C, respectively. An armor layer ratio greater than 3 was identified as a trigger to indicate the potential need for gravel augmentation. BakerGravel_SA108_2016MonitoringResults_ docx Page 3 Draft 1 February 2017

19 Executive Summary Figure 3. Armor ratio in 2013 and 2015 at Sites A, B, and C on the Skagit River (next analysis to be conducted in 2017). Sub-sampling analyses were conducted in 2012 to determine the relationship between sample size and the accuracy of surficial substrate assessments. Analyses of the pebble count data indicated that similar annual precision may be achievable with fewer pebble measurements. Although annual precision may not appreciably change when reducing pebble counts from 100 per transect to 50 per transect (n=500), one year of data did not allow an evaluation of the influence of even minor changes in precision when evaluating a trend analysis (i.e., variance among years). Monitoring objectives are to detect an absolute change in percent substrate greater than 6 inches over 10 years using linear regression trend analysis. The statistical probability of detecting an increase of 10% in percent of sediment particles greater than 6.0 inches after 10 years was evaluated based on the first 3 years of substrate data. The variance of the linear regression slope for each site was estimated using the Mean Squared Error (MSE) from a one-way analysis of variance with year as the main effect, divided by the sum of squared deviations in a sequence of ten years (Zar 1996). This variance estimate includes variability within and among years. The BakerGravel_SA108_2016MonitoringResults_ docx Page 4 Draft 1 February 2017

20 Executive Summary minimum detectable difference for the slope is the change per year, which in this case is 1%. A simulation was conducted to estimate the effects of reducing sample size on this statistical power to detect trends. The simulated scenarios were formed by reducing the number of samples per transect from 100 to 50 or 20. For 50 samples per transect, every second transect was selected from the data for each site, and the power computed as before. Because there were two ways to select these transects for each site (e.g., even or odd numbered points), both estimates were made, and the highest MSE estimate was used as a conservative estimate. For 20 samples per transect; only every fifth point along each transect was included in the sample, resulting in five possible samples and five MSE estimates from which the highest was used. Statistical power for detecting trends, precision and bias of the proportion estimate, and precision of the median substrate size were evaluated for the total and reduced simulated scenarios. The statistical power analysis showed that trends of 1% per year would be easily detectable with sample sizes reduced as low as 20 samples on each of 10 transects. However, this would result in some loss in accuracy and precision of the estimate of proportion of substrate greater than 6 inches. The armor ratio depends on both results from the pebble count surveys and results from subsurface samples. The effects of reduced sample size of pebble counts and/or number of subsurface samples on the armor ratio will be evaluated after By that time there will be three years of armor ratio results to analyze. A recommendation on appropriate sample sizes for future monitoring efforts will be made based on the results of these analyses. BakerGravel_SA108_2016MonitoringResults_ docx Page 5 Draft 1 February 2017

21 Introduction 2.0 Introduction Continued operation of the Baker Project interrupts the downstream movement of coarse sediment through the Baker River and the delivery of coarse sediments to the middle Skagit River. Sediment supply and transport is one of the primary geomorphic processes controlling the condition of aquatic habitats in streams and rivers. Rivers where the sediment transport capacity exceeds the sediment supply tend to be dominated by armored beds which degrades the quality of downstream salmonid spawning habitats. The Baker Project is owned and operated by Puget Sound Energy and consists of the Lower Baker Development completed in 1925, and the Upper Baker Development completed in The Baker Project includes facilities located on and adjacent to the Baker River, occupying about 5,200 acres of land within the Mt. Baker-Snoqualmie Forest. The Lower Baker Dam forms Lake Shannon and is located near Concrete, Washington, near the confluence of the Baker and Skagit rivers. Lake Shannon is approximately seven miles long and covers about 2,278 acres at full pool. The Upper Baker Dam forms Baker Lake, located in Whatcom y near the border with Skagit y. Baker Lake is approximately nine miles long and covers about 4,980 acres at full pool. The two existing hydroelectric facilities have a combined capacity of 200 megawatts. Downstream of Lower Baker Dam, the Baker River flows south for approximately 1.2 miles before entering the Skagit River near RM 54. In support of Baker Project relicensing, PSE conducted Study A-24 Part 1 analyzing the hydrology of the Baker and Skagit Rivers (R2 2004a). In addition, a watershed-scale sediment budget was developed for the Baker River basin as part of Study A-24 Part 2 (R2 2004b). Study A-24 Part 2 also concluded that approximately 12,500 tons of gravel are annually interrupted from downstream transport in the Baker River. However, based on historic aerial photos and available literature on the geomorphology of the middle Skagit River, interruption of bedload from the Baker River had not resulted in observable geomorphic changes in the middle Skagit River. The Baker River Gravel Management Plan (BRGMP) (PSE 2012) was prepared for the Baker Project pursuant to the Order on Offer of Settlement, Issuing New License and Dismissing Amendment Application as Moot dated October 17, 2008 (the license ). Specifically, settlement agreement article 108 (SA 108), Gravel sets forth guidelines and objectives to evaluate and monitor channel and substrate conditions of the lower Baker River alluvial fan and affected reaches of the Skagit River downstream and immediately upstream of the Baker River confluence and to implement gravel augmentation measures if warranted (figure 4). On March 2, 2011, the Federal Energy Regulatory Commission approved the management plan and required that an implementation plan be developed within one year. The BRGIP (PSE 2012) describes monitoring procedures, conditions that will trigger augmentation, and identifies potential augmentation measures. Monitoring includes measuring river bed profiles to assess channel response, and recording multiple Wolman pebble counts and subsurface sediment sampling to assess substrate response. Monitoring of river bed profiles and Wolman pebble count surveys have been performed in 2012, 2013, 2014, 2015 and 2016, and will continue to be conducted BakerGravel_SA108_2016MonitoringResults_ docx Page 6 Draft 1 February 2017

22 Introduction annually. Subsurface sampling was performed in 2013 and 2015, and will be conducted 2017, and then will be conducted at 10-year intervals. Results of the first four years of monitoring (2012, 2013, 2014 and 2015) have been previously documented (R2 2013a, 2013b, 2014 and 2016). Submit BRGMP to FERC FERC Approval Implementation Plan Identify Potential Augmentation Measures Develop Monitoring Procedures Identify Augmentation Triggers Monitoring No Does Monitoring Show Trend of Reduced Gravel Recruitment? Yes No Gravel Augmentation Warranted? Yes Develop Gravel Augmentation Proposal Review and Approval Permitting Implement Gravel Augmentation Figure 4. Process flow chart for implementation of SA 108 Gravel for the Baker River Hydroelectric Project. BakerGravel_SA108_2016MonitoringResults_ docx Page 7 Draft 1 February 2017

23 Background 3.0 Background SA 108 requires that the Licensee shall develop the plan in a manner that considers cost-effective evaluation measures and does not require a comprehensive assessment of sediment dynamics in the Skagit River Basin. However, understanding the geomorphic and sediment transport processes affecting the middle Skagit River provides context for monitoring and gravel augmentation measures. 3.1 Geomorphic Equilibrium A river is considered to be stable in a geomorphic sense when the cross-sectional dimensions (width and depth), longitudinal slope, and substrate surface texture have adjusted to convey the water and sediment supplied to the river with no changes to the long-term averages of these characteristics (Biedenharn et al. 2008). A river with this condition of stability is referred to as a graded stream (Mackin 1948). A graded stream may exhibit temporary morphological changes in response to large floods. The stream may be restored to its graded condition by subsequent moderate floods. A river that responds in this manner to the hydrologic regime is said to be in dynamic equilibrium. The geometric and sediment characteristics of a graded stream may fluctuate from yearto-year but the long-term average of these characteristics will remain stable. If a stream is not in grade, then the geometric and sediment characteristics will trend towards a new equilibrium value and approach it asymptotically. The gradual approach to a new dynamic equilibrium of a disturbed stream may take decades, and it may require 10 years of monitoring to determine whether a stream is in dynamic equilibrium or whether it is evolving towards a new dynamic equilibrium. The alteration in streamflows and the interruption in sediment transport that accompany the operation of a water control reservoir can initiate downstream changes in channel morphology affecting habitat conditions, riparian communities and aquatic ecology. Reservoir operations can result in the reductions in both peak flows and base flows, alteration in seasonal runoff patterns, and trapping of sediments from upstream in the watershed. A common response to these actions is coarsening and degradation of the streambed just downstream from a dam. These effects will gradually attenuate in the downstream direction as the river receives sediment from downstream sources. 3.2 Skagit River Geomorphic Process Conditions The Baker Project affects the morphological regime of the downstream Skagit River in two different ways. First, the downstream supply of bedload from the Baker River has been blocked by the ongoing storage of gravels and cobbles in Baker Lake and Lake Shannon. Secondly, the capacity to transport gravel through the middle Skagit River reach has been reduced as a result of flow regulation for flood management by the Baker Project. These two processes tend to offset each other, but the net result is unknown. Evaluating the downstream effects of the Baker Project is complicated by changes in the sediment supply and transport processes of other Skagit River basin tributaries (figure 5). BakerGravel_SA108_2016MonitoringResults_ docx Page 8 Draft 1 February 2017

24 Background Figure 5. Schematic of middle Skagit River hydrography, river miles and bedload transport drainage areas. Morphological characteristics of the middle Skagit River have been affected by conditions in the Skagit River upstream of the Baker River confluence. The supply of bedload to the Skagit River downstream from Seattle City Light s Skagit River Project (FERC No. 553) has been blocked by the trapping of bedload in Ross Lake, Diablo Lake, and Gorge Lake. While the reservoirs have blocked the downstream transport of bedload from 1,164 mi 2 of drainage area, the capacity to transport gravel through the Skagit River has been reduced as a result of flow regulation by the Skagit River Project. The reduced sediment transport capacity associated with flow regulation tends to reduce the downstream effects of bedload trapping. The middle Skagit River from Gorge Dam at RM 96.6 downstream to below the Baker River confluence at RM 56.5 represents 1,273 mi 2 of uninterrupted bedload transport and unregulated flows. The Sauk River has been the largest source of bedload to this reach of the Skagit River. The Sauk River joins the Skagit River at RM 67.2 and contributes bedload from a drainage area of 733 mi 2 (figure 5). Flows in the Sauk River are unregulated; and the uninterrupted sediment supply in the Sauk River basin has been about 1.5 times the normal sediment yield as a result of logging, roads and Glacier Peak meltwater (Beamer et al. 2000). Increased sediment load from unregulated tributaries downstream of the Skagit River Project may gradually offset the effects of trapping bedload in the Ross, Diablo and Gorge lakes, but the net result has not been determined. The Baker Project blocks the downstream supply of bedload from 179 mi 2 of drainage, not including the 118 mi 2 of drainage upstream of historic Baker Lake. The Baker River joins the middle Skagit River at RM 56.5 and the middle Skagit River is influenced by the BakerGravel_SA108_2016MonitoringResults_ docx Page 9 Draft 1 February 2017

25 Background potentially offsetting processes of reduced bedload supply and reduced sediment transport capacity. Downstream of the confluence with the Baker River, the drainage area of the middle Skagit River increases about 14 mi 2 in 9 river miles. This 9-mile reach of the middle Skagit River extending to just above the Finney Creek confluence will exhibit the greatest effects of the Baker Project since there is little sediment and flow input. Finney Creek joins the middle Skagit River at RM 47.5 and contributes uninterrupted bedload and unregulated flow. Between 1940 and 1979, sediment delivery to the Finney Creek channel due to landslides was relatively constant, but increased 300 percent in the period (Parks 1992). From the Finney Creek confluence to just downstream of the Day Creek confluence at RM 36.5, the middle Skagit River receives uninterrupted bedload and unregulated flow from 200 mi 2 of drainage area in approximately 11 miles of middle Skagit River. The sediment supply from this drainage area has been much higher than normal as a result of logging and roads (Beamer et al. 2000). This increase in sediment delivery will tend to mask potential downstream effects of the Baker Project. From downstream of the Day Creek confluence to the pipeline crossing at Sedro- Woolley at RM 24.5, the contributing drainage area of the middle Skagit River increases 50.1 mi 2 in about 12 river miles. 3.3 Future Skagit River Geomorphic Process Conditions In the future, the Baker Project will continue to trap bedload and regulate flows for flood management. The Skagit River Project in the upper Skagit basin will continue to trap bedload and regulate downstream flows for flood management. Ongoing changes in land use practices may reduce the sediment supply of unregulated tributaries, but the potential effects of climate change on the supply of glacially-derived sediments in the Sauk River are difficult to predict. Climate change may also affect the magnitude and frequency of winter high flow events and affect the future sediment transport capacity of unregulated tributaries. The cumulative effects of these future conditions on the middle Skagit River are unknown. Monitoring to be implemented in response to SA 108 will identify if gravel augmentation measures are warranted to improve the geomorphic function of the lower Baker River alluvial fan and affected reach of the middle Skagit River. 3.4 Distribution of Spawning Salmonids in the Skagit River Bedload transport from the lower Baker River was affected following construction of Lower Baker Dam in Rivers where the sediment transport capacity exceeds the sediment supply tend to be dominated by armored beds which degrades the quality of downstream salmonid spawning habitats. Evidence of significant bed armoring can be associated with the longitudinal distribution of salmonid redds. Coarsening of substrates in response to reductions in sediment supply may reduce the density of redds in downstream gravel-starved reaches; however, salmonid redd distribution may also be affected by channel morphology, flow characteristics, spawner escapement, and other factors unrelated to substrate conditions. Identifying the causal mechanism for redd distribution is often difficult, but salmonid redd distribution is a potential indicator of substrate conditions. BakerGravel_SA108_2016MonitoringResults_ docx Page 10 Draft 1 February 2017

26 Background Conducting salmonid spawning surveys requires clear water conditions to view redds. Water conditions in the middle Skagit River below the Baker River confluence are frequently turbid during late summer and early fall months due to glacial and snowfield meltwater. Cool fall weather can reduce glacial runoff and allow downstream waters to clear, but fall rainstorm events can cause prolonged periods of turbidity. Conducting consistent spawning surveys in the middle Skagit River is difficult due to the variable nature of survey conditions and available spawning survey data are scarce. During relicensing studies, PSE made a concerted effort to collect salmonid redd survey data, and between 2002 and 2005, a total of 18 fall aerial redd surveys and 12 spring aerial redd surveys were successfully conducted in the middle Skagit River between the Baker River confluence at RM 56.5 and Sedro-Woolley at RM 24.5 (Hilgert et al. 2008). These data are supplemented by the results of two springtime aerial redd surveys conducted by WDFW in The Skagit River extending from the Baker River confluence at RM 56.5 downstream to Sedro-Woolley at RM 24.5 supports spawning by fall Chinook salmon (Oncorhynchus tshawytscha), pink salmon (O. gorbuscha), chum salmon (O. keta) and steelhead (O. mykiss). The results of the surveys suggest that conditions in the 9-mile reach of the middle Skagit River between the Baker River confluence and Finney Creek during 2002 through 2005 did not prevent spawning salmonids from constructing redds. In the 32- mile reach between the Baker River confluence and Sedro-Woolley, Chinook salmon constructed as average of 40.1 redds per mile. The 9-mile reach immediately below the Baker River confluence had an average of 28.6 redds per mile, less than the 32-mile reach average, but higher than the average of 18.7 redds per mile observed in the 10-mile reach upstream of Sedro-Woolley. Pink salmon redd surveys indicated few redds in the 9-mile reach immediately below the Baker River confluence; however, chum salmon redd counts were 50 percent higher in the 9-mile reach immediately below the Baker River confluence compared to 32-mile reach average. Steelhead redds were low during the period and averaged 5.2 redds per mile in the 32-mile reach below the Baker River confluence compared to 3.8 redds per mile in the 9-mile reach between the Baker River confluence and Finney Creek. The distribution of salmonid redds is affected by multiple factors, and while significant bed armoring may be associated with a scarcity of redds, salmon redd distributions are not likely to identify minor changes in substrate composition. BakerGravel_SA108_2016MonitoringResults_ docx Page 11 Draft 1 February 2017

27 Monitoring Procedures 4.0 Monitoring Procedures 4.1 Monitoring Objective The objective of the monitoring procedures is to evaluate geomorphic conditions in the middle Skagit River to determine if there is a trend of reduced gravel recruitment that could trigger gravel augmentation under SA 108. Gravel augmentation will be triggered by: Condition of the middle Skagit River absent project influence; Fluvial geomorphic changes throughout the license term; and/or Habitat suitability for salmonids or other aquatic organisms. 4.2 Area According to the BRGMP, the plan area includes the lower Baker River alluvial fan and affected reaches of the Skagit River downstream and immediately upstream of the Baker River confluence. The monitoring area includes the Skagit River from the Baker River confluence (RM 56.5) upstream to the Sauk River confluence (RM 67.2) and downstream to Finney Creek confluence (RM 47.5). The Sauk River is a major upstream source of flow and sediment; and the 11 mile reach downstream of Finney Creek drains approximately 200 mi 2 of watershed and is another major source of sediment. 4.3 Monitoring Procedures A common response to bedload trapping is channel degradation until an armor layer of sediment particles too big to erode becomes exposed. These effects will be most apparent near the source of the disturbance, and will attenuate in the downstream direction as the river receives gravel input from downstream sources. To monitor these potential effects, channel degradation was assessed by establishing and surveying reference cross-sections on the Skagit River. Surficial substrate coarsening was assessed by establishing and monitoring Wolman pebble count (Wolman 1954) transects on gravel bars of the middle Skagit River. Subsurface sampling was also conducted to determine differences in the ratio of surface to subsurface sediment using the median particle grain size to evaluate the degree of armoring. The armor ratio should reflect differences in the local sediment transport rate for a given discharge and sediment supply and provides another indication of sediment characteristics in the Skagit River immediately above and below the Baker River confluence. Channel Response Transects Skagit River degradation above and below the Baker River confluence was monitored by surveying channel bed elevations (with respect to NAVD 88) at sets of three transects located at three sites. Cross-section profiles are used to quantify elevation changes at a site upstream of the Baker River confluence and at two middle Skagit River sites located between the Baker River confluence and Finney Creek. Transects are located in representative habitats while avoiding transects in constrictions, multiple channel areas, or areas artificially constrained by levee or rip-rap. Transects are spaced at approximately bankfull-width intervals and were selected in coordination with ARG representatives. BakerGravel_SA108_2016MonitoringResults_ docx Page 12 Draft 1 February 2017

28 Monitoring Procedures Cross-sections alignments were established by installing headpins on the right and left banks of the river. The horizontal locations of the headpins were surveyed with GPS and total station to allow long-term year-to-year comparisons. If any of the headpins are disturbed or removed they can be re-established from the GPS and total station coordinates. Channel cross-sections were surveyed from bankfull to bankfull (NAVD 88). The bankfull elevation determined during the first survey is used as a reference elevation for subsequent surveys. Stations were measured at bank toes and at intervals spaced approximately every 10 feet across the channel. The bankfull elevation and cross-section profiles are used to consistently calculate average bed elevation during each survey (see section 5.1). Locations of the channel response transects are shown in figure 6. Three reference transects were established at each of the following three sites: 1. Upstream of Baker River confluence but below Sauk River confluence near the inflection point between two bends (Site A, RM 61). 2. Downstream of Baker River confluence in bar habitat, upstream and around the channel bend from the USGS gage (Site B, RM 55). 3. Upstream from Finney Creek confluence near Piscatore Lane (Site C, RM 51.5). Surficial Substrate Response Wolman Pebble s The Wolman pebble count technique is used to quantify the grain-size distribution of sediment on the surface of a stream bed. The grain size distribution can be used to indicate changes in sediment composition and habitat suitability. The sizes of sediment particles on the surface of a gravel bar are naturally sorted by higher flows that transport gravel and shape the morphology of the stream bed. Sediment particles are sorted in both the downstream and lateral directions on a gravel bar (U.S. Army Corps of Engineers 1993). Larger sediment particles are typically found on the upstream end of a gravel bar, and smaller sediment particles are typically found on the downstream end of a gravel bar. In the lateral direction, larger sediment particles are found on the lower portion of the gravel bar closer to the thalweg and smaller sediment particles are found on the higher portion of the gravel bar closer to the bankfull elevation. The Wolman pebble count technique requires the observer to measure sizes of random sediment particles along the streambed. A step-toe procedure is frequently used to randomly select particles for quantification. Starting at a randomly selected point along a transect, the observer takes one step and while averting their eyes, picks up the first particle touching their index finger next to their big toe. The observer measures the intermediate axis and records the particle size in the data book. Measurements of 100 particles are recorded per count in order to accurately quantify pebble distributions. BakerGravel_SA108_2016MonitoringResults_ docx Page 13 Draft 1 February 2017

29 Monitoring Procedures Figure 6. Plan area of the Baker Gravel Implementation Plan showing general transect, Wolman pebble count, and subsurface sampling locations. BakerGravel_SA108_2016MonitoringResults_ docx Page 14 Draft 1 February 2017

30 Monitoring Procedures A sampling strategy designed to encompass this range of natural variability of sediment size on a gravel bar is illustrated in figure 7. Sediment particle sizes on the bars will be accessible, and representative of the size of sediment that is moving through the system. Initially, a total of 10 pebble count transects were established along the length of the gravel bar. A pebble count head pin was established at the highest point of each transect and the horizontal position surveyed with GPS. From each head pin, the transect extended towards the other streambank as far as can be safely waded. To ensure a consistent transect length from year-to-year, the pebble counts were collected when the daily average flow in the Skagit River near Concrete (USGS gage No ) was about 9,000 cfs (see section 4.4). With 10 pebble counts per gravel bar during the initial year, and 100 measurements per pebble count, there were a total of 1,000 particle measurements per gravel bar. Following the first six years of monitoring, results will be analyzed to determine an appropriate sample size for subsequent efforts to determine trends (see section 5). The approximate locations of the sites for pebble count surveys are shown in figure 7. Ten pebble counts were obtained from the following three sites: 1. Along bar near RM 61 upstream of Baker River confluence but downstream of Sauk River confluence (Site A, n=1,000 particle measurements) 2. Along point bar at RM 55, at an area downstream of the Baker River confluence and will provide the closest indication of Baker Project-related substrate coarsening; would also provide feedback on effects of gravel augmentation if it were implemented (Site B, n=1,000 particle measurements). 3. Along north bank gravel bar at Piscatore Lane at RM 51.5 at an area that historically has supported salmon spawning activity (Site C, n=1,000 particle measurements). Subsurface Substrate Response Armor Ratio The vertical structure of gravel deposits can vary depending on the supply of transportable sediment in the streambed, the bed-material particle-size distribution, and the interaction of flow hydraulics. The vertical profile of a streambed usually shows that particle-size distributions do not change gradually with depth, but change abruptly in the form of layers. The particle-size distribution in each layer is the result of an interaction between flow hydraulics and sediment. The strata can therefore be used to obtain information on the amount of sediment supplied to the stream, the sediment particle sizes, and the manner in which the sediment was transported and deposited. The degree of bed armoring may be quantified by the ratio of the D50 surface sediment size to the D50 subsurface sediment size. This ratio approaches a value close to 1 in streams with high sediment supply, whereas streams in which transport capacity exceeds sediment supply, the ratio approaches a factor of approximately 2. The ratio of D50surf/D50sub may exceed a value of 3 in high-energy mountain streams or when sediment supply is shut off and a coarse lag deposit forms. BakerGravel_SA108_2016MonitoringResults_ docx Page 15 Draft 1 February 2017

31 Monitoring Procedures Figure 7. Example alignment of Wolman pebble count transects on a Skagit River gravel bar. The initial set of subsurface samples was collected in 2013 and a second set of subsurface samples was collected in One sample was collected from each of the ten pebble count transects established at each site. Samples were collected in shallow water using a deep plastic ring (e.g., trash container cut in half with bottom removed) to shelter the extraction area from sweeping flow. The ring was placed over the streambed, and the surface layer of sediment (defined by the depth of the largest particle on the surface) was removed by hand from the area defined by the drum. The subsurface sample was then collected from this area and place in a bucket. The total dry weight of each sample was about 30 kilograms. The samples were wet-sieved through a series of standard metric wire mesh sieves and the volumetric displacement of material retained on each sieve was measured to the nearest 10 millimeters. The portion of each sample retained on the 2 mm sieve (2 to 4 mm in size) was stored in a zip-lock plastic bag and brought back to the laboratory to determine the specific gravity of the sediment. Determination of specific gravity was needed to subsequently correct the measured wet volumes in the field to account for the portion of the wet volume comprised only of dry sediment. This correction was based on adjustments recommended by Shirazi and Seim (1979). BakerGravel_SA108_2016MonitoringResults_ docx Page 16 Draft 1 February 2017

32 Monitoring Procedures The combined weight of all ten samples collected from each site was about 300 kilograms. This quantity is sufficient to avoid potential bias if the largest sediment particle collected is less than about 230 mm (7.5 inches, American Society for Testing and Materials). After this first two rounds of subsurface sampling in 2013 and 2015, a subsequent sample will then be collected in 2017, and then at 10-year intervals in 2027, 2037, etc. through the duration of the license. After the initial round of sampling, the variability of the size composition of the subsurface samples was assessed to evaluate the number of samples needed to reflect substrate conditions. 4.4 Timing and Frequency Initiate transect selection within 1 year of FERC approval of the BRGMP (March 2, 2011) to establish a baseline. Measure transects and conduct surficial substrate assessments annually (starting in 2012) during August, September or early October prior to the onset of fall rains. Conduct subsurface sampling in 2013, 2015 and 2017, and then at 10-year intervals. Measure transects and conduct substrate assessments when the daily average flow in the Skagit River below Baker River confluence (USGS No ) is about 9,000 cfs to provide consistent annual survey conditions and area of streambed exposure. The target flow level represents a low flow during wet years and a moderate flow during dry years. In addition to reporting requirements described in the BRGMP, PSE will present and discuss the results of gravel monitoring activities to the ARG at a gravel monitoring meeting to be scheduled each spring. BakerGravel_SA108_2016MonitoringResults_ docx Page 17 Draft 1 February 2017

33 Augmentation Trigger 5.0 Augmentation Trigger In response to SA 108, PSE has committed to gravel augmentation independent of project effects. As defined in SA 108, augmentation triggers will consider the following: Condition of the middle Skagit River absent Baker Project influence; Fluvial geomorphic changes throughout the license term; or Habitat suitability for salmonids or other aquatic organisms. The process to implement gravel augmentation would be triggered by a demonstrated trend of reduce gravel recruitment as evidenced by either a channel response or a substrate response. 5.1 Channel Response Channel response in the Skagit River will be monitored by surveying the channel bed profile to actual elevations (NAVD 88). The bankfull elevation and surveyed channel profile for each transect measured during the initial survey will be used to calculate a bankfull depth, as illustrated in figure 8. A site-averaged bankfull depth was determined from the three transects surveyed at each site. A bankfull area was determined for each of the three transects (A 1, A 2, and A 3 ). Similarly a bankfull top width was determined for each of the three transects (TW 1, TW 2, and TW 3 ). The site-averaged bankfull depth was then determined from the following formula: Site Averaged Bankfull Depth = A1 + A2 + A3 TW + TW + TW The gravel augmentation process will be initiated if the site-averaged bankfull depth has increased more than 10 percent at two adjacent transect monitoring locations over a minimum 10 year period. An example of how this might occur is shown in figure Surficial Substrate Response Assuming that ten, 100-count Wolman pebble measurements per location provide a reasonable estimate, all Wolman particle measurements per location were combined (n=1,000) to quantify the sediment particle size distribution. The percent of sediment particles greater than 6.0 inches was compared to the total sediment particle size distribution for each location, as exemplified in figure 10. The gravel augmentation process will be initiated if the percent of sediment particles greater than 6.0 inches shows an increasing trend of greater than 10 percent of the total distribution at two adjacent sites over a minimum 10 year period. An example of how this might occur at a site is shown in figure 11. Changes in substrate size composition may be observed prior to changes in bed elevation. Substrate coarsening at two adjacent reaches will likely be caused by upstream effects and a minimum 10-year trend will ensure that the observed change is not the result of a short-term or localized fluctuation BakerGravel_SA108_2016MonitoringResults_ docx Page 18 Draft 1 February 2017

34 Augmentation Trigger 180 Elevation (feet, NAVD 88) Bankfull Top Width = 651 feet Bankfull Elevation Bankfull Depth Bankfull Area = 6,060 ft 2 Bankfull Depth = Bankfull Area/Bankfull Top Width = 9.3 feet Average Bed Elevation = Bankfull Elevation - Bankfull Depth Horizontal Station (feet) Figure 8. Example of bankfull depth calculation of a cross-section of the Skagit River. 15 Bankfull Depth (feet) % of Bankfull Depth in Year Zero Bankfull Depth in Year Zero Year Figure 9. Example of trend analysis of bankfull depth from a monitoring site on the Skagit River over a 10-year period. BakerGravel_SA108_2016MonitoringResults_ docx Page 19 Draft 1 February 2017

35 Augmentation Trigger % of the substrate is larger than 6 inches % Percent Finer Than Grain 6 inches Figure 10. Example of percent coarse substrate calculation from Wolman pebble count grain size distribution. Percent of Substrate Greater Than 6 inches Percent Coarse Sediment in Year Zero Plus 10% Percent Coarse Sediment in Year Zero Year Figure 11. Example of trend analysis of percent coarse substrate from a gravel bar on the Skagit River over a 10-year period. BakerGravel_SA108_2016MonitoringResults_ docx Page 20 Draft 1 February 2017

36 Augmentation Trigger The initial sampling strategy consisted of collecting 100 sediment particle measurements per transect and ten transects per site in order to quantify surficial substrate size distribution. This provided a sample size of 1,000 particle counts per site. Following the first three years of sampling ( ), the impacts of reducing the number of particle measurements per transect on the statistical probability of detecting trends in particle size were evaluated. The statistical probability of detecting an increase of 10% in sediment particles greater than 6.0 inches after 10 years was evaluated based on the first 3 years of substrate data. The variance of the linear regression slope for each site was estimated using the Mean Squared Error (MSE) from a one-way analysis of variance with year as the main effect, divided by the sum of squared deviations in a sequence of ten years (Zar 1996). This variance estimate includes variability within and among years. The statistical power was estimated for a minimum detectable difference in the slope (change per year) of 1%, which would result in a 10% change after 10 years. A simulation was conducted to estimate the impacts of reducing sample size on this statistical power to detect trends. The simulated scenarios were formed by reducing the number of samples per transect from 100 to 50 or 20. For 50 samples per transect, every second transect was selected from the data for each site, and the power computed as before. Because there were two ways to select these transects for each site (e.g., even or odd numbered points), both estimates were made, and the highest MSE estimate was used as a conservative estimate. For 20 samples per transect, only every fifth point along each transect was included in the sample, resulting in five possible samples and five MSE estimates from which the highest was used. Statistical power for detecting trends, precision and bias of the proportion estimate, and precision of the median substrate size were evaluated for the total and reduced simulated scenarios. 5.3 Subsurface Substrate Response The armor layer ratio of unimpaired gravel-bed rivers typically ranges between 1.0 and 3.0. The armor layer serves as a buffer to regulate the frequency of mobilization of the stream bed. When the armor layer ratio is 1.0, the streambed will be frequently mobilized, and the river may be at risk of aggradation. As the armor layer ratio increases from 1.0 to 3.0, the streambed will be mobilized less frequently, and the armor layer will serve to protect the stream bed from scouring. When the armor layer ratio exceeds 3.0, this reflects a condition where the streambed will scour down and the surface will be coarsened until the streambed is rarely mobilized. This condition would be very undesirable for spawning salmonids. An armor layer ratio of 3.0 was selected as a trigger to indicate the potential need for gravel augmentation. Trend analyses will not be performed to assess this potential need. If the armor layer ratio exceeds 3.0 in any particular year of sampling, then this would trigger the potential need for augmentation. BakerGravel_SA108_2016MonitoringResults_ docx Page 21 Draft 1 February 2017

37 Monitoring Results 6.0 Monitoring Results Gravel monitoring sites were initially selected on February 21, 2012 at the locations shown in figures 12, 13, and 14 for Sites A, B, and C, respectively. The average flow on that date in the Skagit River near Concrete (USGS Gage No ) was 13,900 cfs. During the 2016 field effort, ground-based surveying was performed at each site with a Sokkia Set 500 total station instrument. The dry and wadeable portion of each transect was surveyed with the total station instrument, and the rest of the cross-section was surveyed from a jet boat using a Hydrolite TM. This system includes a Sonarmite MILSpec echo sounder. This is a 200 KHz single beam sounder with a beam width of 4 degrees, capable of measuring depths as shallow as 0.3 m (1 ft). Output from the echo sounder was transmitted via Bluetooth to a Trimble GeoXM. Depths were recorded on the Trimble GeoXM using Sonarmite PDA software, along with concurrent GPS coordinates. Pebble count surveys were conducted at Site A on August 23, 2016 when the daily average flow in the Skagit River near Concrete (USGS Gage No ) was 6,430 cfs. The distance between pebble count transects at Site A was about 58 ft. Groundbased cross section surveys and bathymetric surveys were performed at Site A on August 22 and 23, 2016 (6,710-6,430 cfs). Pebble count surveys were conducted at Site B on August 24, 2016 when the daily average flow in the Skagit River near Concrete (USGS Gage No ) was 6,380 cfs. The distance between pebble counts transects at Site B was about 52 ft. Groundbased cross section surveys and bathymetric surveys were performed at Site B on August 22 and 23, 2016 (6,710-6,430 cfs). Pebble count surveys were conducted at Site C on August 24, 2016 when the daily average flow in the Skagit River near Concrete (USGS Gage No ) was 6,380 cfs. The distance between pebble count transects at Site C was about 115 ft. Groundbased cross section surveys and bathymetric surveys were performed at Site C on August 22 and 24, 2016 (6,710-6,380 cfs). When the pebble counts were surveyed and the subsurface samples were collected in 2016, flows in the Skagit River near Concrete were lower than the targeted flow of 9,000 cfs. Normally, the pebble counts would be collected along transects that extended into the river where it could be safely waded. BakerGravel_SA108_2016MonitoringResults_ docx Page 22 Draft 1 February 2017

38 Monitoring Results Figure 12. Locations of cross-section transects and pebble count surveys in Skagit River downstream from Sauk River Confluence and upstream from Baker River Confluence, Site A. Figure 13. Locations of cross-section transects and pebble count surveys in Skagit River downstream from Baker River Confluence and upstream from USGS Gage No (Skagit River near Concrete), Site B. BakerGravel_SA108_2016MonitoringResults_ docx Page 23 Draft 1 February 2017

39 Monitoring Results Figure 14. Locations of cross-section transects and pebble count surveys in Skagit River at Piscatore Lane, Site C. 6.1 Cross-Section Profiles Results of cross-section profile surveys from 2012 through 2016 at Site A are shown in Figures 15, 16, and 17 for Transects TRA1, TRA2, and TRA3, respectively. Crosssection profiles at Transect TRA1 were generally similar from 2012 through 2016, with the exception of net aggradation occurring on the left swale/channel in Crosssection profiles at Transect TRA2 show little net aggradation from 2015 to 2016, but the 2016 data shows a leftward shift of the main channel. Notable aggradation was observed at TRA3 Between 2015 and 2016, specifically the partial rebuilding of a right-side bar that was present in , and the depositing of material on the left side of the cross section beyond which has previously been observed. The left bank of TRA3 is convoluted with large woody debris, so it s unclear if this change observed on the left reflects true deposition or rather reworking of material around the debris. This area will be monitored in future surveys. The site-averaged bankfull depths at Site A in 2012, 2013, 2014, 2015 and 2016 were 21.6 ft, 21.6 ft, 21.5 ft, 22.0 ft, and 21.4 ft respectively. The decrease in bankfull depth between 2015 and 2016 is a result of the aggradation seen primarily in TRA1 and TRA2. Note, however, that the 2016 site-averaged bankfull depth at Site A is similar to the values observed in Results of cross-section profile surveys from 2012 through 2016 at Site B are shown in figures 18, 19, and 20 for Transects TRB1, TRB2, and TRB3, respectively. The crosssection profiles have been generally similar from 2012 through 2016 for all three transects. The site-averaged bankfull depths at Site B in 2012, 2013, 2014, 2015 and 2016 were 20.7 ft, 20.7 ft, 20.6 ft, 20.6 ft, and 20.6 ft respectively. BakerGravel_SA108_2016MonitoringResults_ docx Page 24 Draft 1 February 2017