Gravel Extraction Annual Monitoring Report

Transcription

1 P.O. Box 712 Scotia, CA Phone (707) Fax (707) Gravel Extraction Annual Monitoring Report Middle Reach of the Eel River Humboldt County CA Encompassing gravel bars: Scotia Upper and Lower Truck Shop Dinner Creek Three-Mile Elinor Larabee/Holmes South Fork Bowlby Vroman Maynard December 1, 2011

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3 GRAVEL EXTRACTION ANNUAL MONITORING REPORT MIDDLE REACH OF THE EEL RIVER 2011 Report Prepared by: Kate Sullivan David Manthorne Mark Freitas Amanda Pelletier Jason Butcher 3 P a g e

4 Primary Author Kathleen Sullivan, PhD. Forest Operations Manager Thomas Schultz 125 Main Street Scotia, CA P a g e

5 TABLE OF CONTENTS Table of Contents... 5 List of Tables... 6 List of Figures... 6 Introduction... 7 Study Area... 8 Gravel Extraction History Climate Cross-section Monitoring Methods Methods Cross-section Monitoring Results Cross-sectional Area Thalweg Elevation Mean Bed Elevation Patterns in Bed Elevation in Relation to Extraction Volume Patterns Evident at Individual Bar Cross-sections Habitat Monitoring Methods Macro-habitat Habitat Surveys Micro-habitat Surveys Aerial Photography, Mapping and GIS Processing Results Habitat Mapping Macro-Habitat Channel Unit Distribution Pool Depths Salmonid Habitat Habitat Summary Recommendations... Error! Bookmark not defined. References Appendices A. Ortho-photos of the surveyed river reach B. Cross-sections Drafted per LOP specifications... Error! Bookmark not defined. C. Cross-sections Plotted by... Error! Bookmark not defined. D. Summarized cross-section data... Error! Bookmark not defined. E. Habitat Field data forms P a g e

6 LIST OF TABLES Table 1. Gravel bars operated by Humboldt Redwood Company on the M. Reach of the Eel R Table 2. History of gravel extraction by bar and by year (cubic yards) Table 3. Monitoring cross-sections in the Middle Reach Eel River Table 4. Coverage of aerial photos in submittal package Table 5. Distribution of macro-habitat lengths in the Middle Reach Eel River Table 6. Macro-habitat unit characteristics measured in Table 7. Depth characteristics of individual pool units in Table 8. Comparison of pool depth characteristics in the Middle Reach of the Eel River Table 9. Summary of micro-habitat area for 2007 to Table 10. Area contained within four types of salmonid-micro-habitats in the Middle Reach of the Eel River LIST OF FIGURES Figure 1. Middle Reach of the Eel River looking downstream from the confluence with the S. Fork Eel River... 9 Figure 2. Gravel extraction bars within the Middle Reach Eel River Figure 3. History of gravel extraction in the Middle Reach of the Eel River since Figure 4. Annual record of instantaneous peak discharge (A) and 7-day low flow at the U.S.G.S. gauging station at Scotia, CA ( ) Figure 5. Change in cross-sectional area averaged at the bar and reach scale Figure 6. Cross-sectional area under a datum averaged for each gravel bar by year Figure 7. Net change in thalweg elevation averaged at the bar and reach scale Figure 8. Thalweg elevation averaged by bar from 1999 to Figure 9. Definition sketch of mean depth calculation. Mean depth is the average elevation of the points under the reference elevation within the hatched area Figure 10. Net change in mean channel elevation averaged at the bar and reach scale Figure 11. Mean bed elevation averaged for each gravel bar by year Figure 12. Relationship between annual extraction volume and the average reach thalweg elevation for the Middle Reach of the Eel River Figure 13. Relationship between annual extraction volume and the average bed elevation for the Middle Reach of the Eel River Figure 14. Relationship between annual extraction volume and the average reach thalweg depth for the Middle Reach of the Eel River Figure 15. Relationship between annual extraction volume and the average bed depth for the Middle Reach of the Eel River Figure 16. Scotia Bar cross-sections 1 and Figure 17. Cross-sections on Vroman Bar plotted by year Figure 18. Example photo map created by HRC GIS department of gravel bar and habitat features P a g e

7 INTRODUCTION Humboldt Redwood Company extracts gravel from the Middle Reach of the Eel River in the vicinity of Scotia, California under Vested Rights granted by Humboldt County. HRC follows all permits regulating this activity and conducts annual monitoring according to requirements of the U.S. Army Corps of Engineers Letter of Permission. This includes monitoring of channel dimensions through cross-section surveys and habitat features defined for threatened salmonids that utilize the river for migration, spawning, and rearing. The hydraulic characteristics of the flow of water and sediment during peak storms creates a systematic channel morphology with deposition of sand and gravel in bars alongside the channel alternating with scoured areas within the channel referred to as pools (Leopold, Wolman, and Miller 1964). Maintenance of this channel morphology within river reaches where gravel is commercially extracted is critical to provide necessary habitat conditions for salmonids. Gravel bar and channel thalweg morphology results from the equilibrium of sediment input to and exported from each river reach. A channel in equilibrium cutting and filling is efficient at maintaining its geomorphic form and pattern as it responds to cyclic floods and sediment delivery events. A river reach may be stable with bar deposits remaining in one location as sediment migrates from one to the next, typically where the channel is constrained between adjacent hillslopes, or the channel itself may gradually migrate by eroding sediment from the outside of bends (sediment loss) and depositing equal volumes on the inside of bends (sediment gain) as occurs on an alluvial floodplain. In either case, the channel morphology is maintained in a dynamic equilibrium with sediment supply and there is typically little net change in storage within in the reach over time. The goal of gravel extraction permits is to ensure that the volume of gravel removed annually remains within the amount recruited by natural sediment transport processes. Gravel extraction operations within a reach may result in bar or reach scale adjustments, especially where multiple sites are excavated. When extraction exceeds recruitment, a variety of impacts may result: Localized or reach-scale bed degradation Shallowing Loss of pools Channel widening Reduced size of bars Increase lateral instability through bank erosion Rapid bank retreat in valleys where channel is more confined, Reduced size of bars Channel topography depicted with cross-sections are indicators of changing bed elevation (aggradation or degradation), and width or depth changes. By comparing one year s survey with another, changes over the intervening time span can be quantified. Since cross-section monitoring began, the history of gravel extraction in the Middle Reach of the Eel River has varied annually from maximum allowable extraction volumes to none with moderate extraction in between. Several bars have experienced almost no extraction during the period while at the 7 P a g e

8 same time; several have been mined almost to their allowable limit (and presumably their average replenishment quotient) for a number of years. Finally, there has been very little extraction within the Middle Reach of the Eel River as a whole after 2003, with extractions in 2007 and 2011 well below allowable limits. This report details results of channel cross-section and salmon habitat unit monitoring of the Middle Reach of the Eel River for the year Methods conform to the Army Corps of Engineers LOP permitting instream gravel extraction operations and CHERT requirements in Humboldt County. STUDY AREA The Humboldt Redwood Company (HRC) extracts gravel from the Middle Reach of the Eel River. The upstream boundary of the Middle Eel Reach begins approximately 5.7 miles above the confluence of the Middle and South Forks of the Eel River, and extends down river approximately 25 miles to the confluence of the mainstem Eel with the Van Duzen River (Figure 2). Ten gravel extraction bars are included in the thirty-three mile long assessment area (Table 1). This is roughly 50% of the bars that occur in the reach. The total combined river bar length (river frontage) is 9.2 miles (27% of the length of the assessment area). The lower five sites are located along the four-mile stretch of river upstream of Scotia (Figure 2). The Holmes-Larabee Bar is relatively isolated about eight miles below the South Fork Eel River confluence. Four of the extraction bars are located in the 5.7 miles above the South Fork confluence. Table 1. Gravel bars operated by Humboldt Redwood Company on the Middle Reach of the Eel River. River Common Name Mile Operator Scotia Dam Bar Truck Shop Bar (2 bars) Dinner Creek Bar Three Mile Bar Elinor Bar Larabee (Holmes) Bar South Fork Bar Bowlby Bar Vroman Bar Maynard Bar Township, Range, and Section T1N, R1E, Sec 7 and 18 T1N, R1E, Sec 18 and 17 T1N, R1E, Sec 20 and 21 T1N, R1E, Sec 21 T1N, R1E, Sec 23 and 28 T1S, R2E, Sec 3 T1S, R2E, Sec 3 T1S, R2E, Sec 26, 25 and 35 T1S, R3E, Sec 30 and 31 T1S, R3E, Sec 29 and Size of Bar 1 (Acres) HRC 26 HRC 32 HRC 24 HRC 33 HRC 54 HRC 44 HRC 41 HRC 48 HRC 59 HRC 40 8 P a g e

9 A determination of Vested Rights for Pacific Lumber Company s (PALCO) Eel River gravel bar operations was approved by the Humboldt County Supervisors in 1995 and transferred to the Humboldt Redwood Company, LLC (HRC) following financial reorganization of the Pacific Lumber Company in bankruptcy proceedings. The total allowed extraction for the entire operation, as per Vested Rights, is 150,000 cubic yards (cy) per year, with continued extraction of river run gravel from any one bar at an average rate of 15,000 cy/year, as averaged over a ten year period, not to exceed 30,000 cy in any given year. The various gravel bars are managed on a rotational extraction basis. Figure 1. Middle Reach of the Eel River looking downstream from the confluence with the S. Fork Eel River (Google Earth). Bull Creek Scotia 9 P a g e

10 Figure 2. Gravel extraction bars within the Middle Reach Eel River. 10 P a g e

11 GRAVEL EXTRACTION HISTORY The history of gravel extraction in the Middle Reach of the Eel River since 1996 is provided in Table 2 and Figure 3. The full allocation has not been extracted from any gravel bar in any year, and no bar has been operated every year. Since 2003, there has been limited gravel extraction in 2007 and Several gravel bars have had very limited or no extraction throughout the permit period from 1996 to Table 2. History of gravel extraction by bar and by year (cubic yards). YEAR SCOTIA DAM TRUCK SHOP DINNER CR. 3-MILE ELINOR River Mile TOTAL ,472 25, ,692 12, , ,407 19, ,381 10,618 12, , ,000 18,287 23,795 17, , , ,869 3,074 24,087 29, ,600 28, , , ,149 24, ,138 20,781 14, , ,786 12,552 2, , , , ,775 27, ,187 26, , ,740 24,195 25, , ,853 20, , , , , ,618 Total 40, ,487 46, , ,355 2, , ,744 40, ,706 Average ,059 8,160 2,524 5,904 2, ,819 2, Holmes/LARABEE SOUTH FORK BOWLBY VROMAN MAYNARD 11 P a g e

12 Annual Extraction (Yd 3 ) Figure 3. History of gravel extraction in the Middle Reach of the Eel River since HRC Extraction--Eel River 200, ,000 Reach Annual Allowable Maximum 160, , , ,000 80,000 60,000 40,000 20,000 0 The general method of extraction within the Middle Reach of the Eel River has been skimming. Several alternative methods have been used in a few years. Trenching was used at Truck Shop Bar in , and A horseshoe extraction was conducted on Three-Mile bar in CLIMATE Annual discharge records from the USGS Scotia Gauging Station ( ) indicate an average peak winter discharge of 180,556 cfs for the period from 1911 to 2011 (Figure 4A). A maximum discharge of 752,000 cfs was reported for 23 December The corresponding gage depth (water depth) for the average peak flow for the period of record is approximately 38 ft. The maximum gage depth (23 December 1964) was 72.0 ft. Peak flows have been relatively low over the past five years. The largest recent storm occurred in hydrologic year This peak ranked 14 th in the 97-year record. Peak stream flow was very low in 2009, and has increased moderately in successive years. Because both high and low flows are important to fish, the record of low flow discharge at the Scotia station is shown in Figure 4B. Available habitat area for summer rearing or water depth for migration from year to year is likely to depend on minimum annual flow. Minimum flow for the hydrologic year occurred in September, Minimum flows were substantially higher in 2010 and 2011 than in the previous 3 years and were near the historic highs. 12 P a g e

13 Discharge (cfs) Peak Discharge (cfs) Figure 4. Annual record of instantaneous peak discharge (A) and 7-day low flow at the U.S.G.S. gauging station at Scotia, CA ( ). 800,000 USGS Annual Peak Discharge Records for Eel River at Scotia ( ) 700, ,000 Average peak discharge for period of record ( ) =181,755 cfs Maximum discharge for period of record 752,000 cfs recorded on 23 December , , , , ,000 0 Water Day Low Flow--Eel River at Scotia P a g e

14 CROSS-SECTION MONITORING METHODS The channel morphology of the 10 gravel bars in the Middle Reach of the Eel River has been monitored at permanent cross-sections that are measured every year. The channel cross section surveys yield topographic information across a slice of river channel perpendicular, or nearly so, to the longitudinal centerline of the high flow channel. The purpose of cross-section monitoring is to track changes in crosssectional channel configuration, channel bed elevations, and river plan view. Low-level aerial photos flown each year, and fish habitat surveys are also used to monitor channel morphology (described in the next section). Channel topography depicted with cross-sections are indicators of changing bed elevation (aggradation or degradation), and width or depth changes. By comparing one year s survey with another, changes over the intervening time span can be quantified. Cross-section labels are provided in Table 3. Table 3. Monitoring cross-sections in the Middle Reach Eel River. Bar Name River Mile Number of Crosssections Cross-section Label Included in CHERT analysis (2009) Size of Bar (Acres) Scotia Dam Bar , 1, 2, 3, 4, 5 0, 2, 3, 5 26 Truck Shop Bar , 7, 8, 9, 10, 11 6, Dinner Creek Bar , 13, Three Mile Bar , 14, 15, 16, 17 15, Elinor Bar A, B, C, D, E, F, I 8, 2 54 Larabee (Holmes) Bar AA, A, D, F 2 (?) 44 South Fork Bar A, B, C, D, E, F 3 41 Bowlby Bar A, B,C, D,E, F 1 (A), 6 (F) 48 Vroman Bar A, B,C, D,E, F 1 (A), 6 (F) 59 Maynard Bar A, B, C B 40 Methods The annual survey of Humboldt Redwood Company s 54 monitoring cross-sections was completed by Sousa Land Surveys, Inc in August through October of All work was done by or under the direct supervision of a California licensed Land Surveyor. On-site survey control was established by performing static GPS control surveys in August through October of Topcon Legacy E, GGD, dual constellation and dual frequency (L1 and L2) GNSS receivers were utilized to observe each of the project s primary control stations. The resulting static observation files were processed against the three nearest Continuously Operating Reference Stations through NOAA s Online Positioning User Service to align the project s control network with the National Spatial Reference System. Control values were then assigned to each cross-section end-point by direct observation from the primary control network stations utilizing either Robotic/Reflectorless total station or Real Time Kinematic (RTK) GPS instruments as appropriate. 14 P a g e

15 Datum: 1. Horizontal Datum: The horizontal datum utilized for the establishment of coordinate values of this survey is the North American Datum of 1983 (NAD83), Reference Frame CORS96, Epoch Date Vertical Datum: The vertical datum utilized for the establishment of orthometric height values for this survey is the North American Vertical Datum of 1988 (NAVD88), determined from Geoid Separation Values derived from the National Geodetic Survey s published Geoid of 2003 (GEOID03). The project s existing control network was recovered during this year s survey and found to be in stable condition. The field survey of all 54 monitoring cross-sections was performed from the project s existing control network. The use of the existing control network ensures a continuous publishing of monitoring data on a consistent control system, allowing this year s data to be directly compared to the previously collected monitoring. The field survey of the monitoring cross-sections was performed utilizing a combination of RTK GPS and total station surveying techniques where appropriate. The conventional surveys utilized a Leica 1203 Plus Robotic Total Station. Cross sections were located in the field by using the endpoint coordinates. Points were collected throughout the width of the channel extending up the sides of the channel to the stable, un-altered ground lying above this year s high-water flow elevation. Points were collected as points on a line between the two endpoint coordinates. Data collection conducted by Sousa Land Surveys was led by Professional Land Surveyor Brian L. Sousa (LS-7917). Mr. Sousa worked in coordination with two field personnel to collect all points presented with a data capture date of Points were collected to best represent grade breaks and other topographical features to comply with the requirements of the 2009 Letter of Permission Procedure, Gravel Mining Activities within Humboldt County, issued by the U.S. Army Corps of Engineers Data Corrections: The monitoring survey conducted in 2010 was completed by Points West Surveying (Arcata, CA) using the same techniques described above. In completing the survey in 2011, we identified potential problems with elevation control in the 2010 survey. This may be due to methods used last year in establishing the GPS network. This year we returned to the control network that has been in place since Corrections to that control are described below by Sousa (2011). We have translated all of last year s survey coordinates to match the existing datums of the sites. Last year s surveys had used a 2009 geoid model as the basis for establishing elevations for the 2010 surveys. This created an issue, as the elevations for all of the sites were based upon the 2003 Geoid. This difference between the two Geoids varies based upon location from 0 to 1'. The reporting sheets that were prepared for last year left the coordinate elevations and historic survey data on the original Geoid 03 site datums and intermingled them with the 2010 data that was based upon the Geoid 2009 elevations. This resulted in the reported data misrepresenting the site conditions at the date of survey. We note that the adjusted data still has some anomalies that may represent real changes in the streambed or may result from the data adjustments. This is apparent when we process the data in a later section of this report, particularly the mean bed elevations (pg ). Adjustments to 2010 survey data are listed below by bar. 15 P a g e

16 2010 Coordinate Adjustments: Scotia Sites: Delta North: -0.45, Delta East: 0.14, Delta Elevation: Elinor: Delta North: -0.42, Delta East: 0.22, Delta Elevation: 0.28 Larabee: Delta North: 0.36, Delta East: -.06, Delta Elevation: South Fork / Bowlby: Delta North: -0.20, Delta East: 0.00, Delta Elevation: Vroman / Maynard: Delta North: -0.42, Delta East: 0.14, Delta Elevation: National Geodetic Survey (NGS) is in the process of issuing a new high resolution Geoid that will be based upon actual gravimetric observations instead of sporadic GPS measurements. This new realization of the NAVD88 datum will result in different control elevations of up to 3 feet. The updated Geoid model is expected to be released in Each time the datum for a site is changed, it can result in confusion and cause interpretation errors. With this in mind, it was not recommended to alter the datum for the sites until the new system is released and well proven. 16 P a g e

17 Maynard Vroman Bowlby South Fork Larabee (Holmes) Elinor Three Mile Dinner Creek Truck Shop Scotia Net Change in Cross-section Area (ft 2 ) Cross-sectional Area (ft 2 ) Cross-section Monitoring Results CHERT is provided the raw data from cross-section surveys and is officially responsible for processing and interpretation of river morphological changes in response to gravel extraction in rivers within Humboldt County. HRC routinely processes the cross-section information we provide to CHERT and the agencies and these results are provided in this report for informational purposes. Following CHERT (2008), we focus on reach and bar-averaged values for cross-sectional area, thalweg elevation, and mean bed elevation. The analysis examines changes in channel dimensions from 1999 to Tabular values for parameters averaged at the bar level and for individual cross-sections for each year is provided in Appendix A. Cross-sectional Area Cross-sectional Area is calculated as the volume of space under a datum above the surveyed crosssection. A decrease in cross-sectional area indicates a net accumulation of gravel (fill). An increase indicates more open volume indicating net scour across the cross-section. At the reach level, there is a pattern in net change in bar cross-sectional area during the 1999 to 2011 time interval (Figure 5A). The change observed at the bars in 2011 relative to area in 1999 was generally about ±2%. The gravel bars in the upper portion of the reach (Elinor Bar upwards) have increased in cross-sectional area (scoured) while lower bars have been accumulating sediment. Bowlby Bar is expanding area due to rapid bank erosion at two cross sections. Individual gravel bars within the Middle Reach of the Eel River have had very different patterns of scour and fill from year to year (Figure 6). A number of bars showed almost no variation in average annual cross-sectional area (Scotia, South Fork, and Larabee), several are experiencing net fill (Three-mile, Dinner, and Truck Shop) and three are scouring (Elinor, Maynard, and Vroman). Bowlby bar appears to be scouring, but this cross sectional change is due to bank retreat by erosion. The channel dimensions within the reach as a whole (Figure 5B) show that the general level of scour in the upper section was sufficient in hydrologic year 2011 to cause net scour for the reach as a whole. Figure 5. Change in cross-sectional area averaged at the bar and reach scale. A). Net change from 1999 to 2010 for each bar. Bars are shown from left to right in order from upstream to downstream. B) Crosssectional area of all bars within the Middle Reach of the Eel River averaged annually. A.) 1000 Middle Reach of the Eel River Change Between 1999 and 2011 B). 10,100 Middle Reach of the Eel River Average all Gravel Bars Scour 10,050 10, , Fill 9,900 9,850 9, P a g e

18 Cross-section Area Below Reference Elevation (ft 2 ) Cross-section Area Below Reference Elevation (ft 2 ) Cross-section Area Below Reference Elevation (ft 2 ) Cross-section Area Below Reference Elevation (ft 2 ) Cross-section Area Below Reference Elevation (ft 2 ) Figure 6. Cross-sectional area under a datum averaged for each gravel bar by year. The datum lies above the active channel area. 9,300 Scotia Bar 7,500 Truck Shop Bar 9,200 7,400 9,100 7,300 9,000 8,900 8,800 7,200 7,100 7,000 6,900 8,700 6,800 8,600 6,700 8,500 6,600 6,500 10,000 9,800 Dinner Bar 12,400 Three Mile Bar 9,600 12,200 9,400 12,000 9,200 9,000 11,800 8,800 11,600 8,600 11,400 8,400 8,200 8,000 11,200 11,000 Elinor Bar 14,400 14,200 14,000 13,800 13,600 13,400 13,200 13, P a g e

19 Cross-section Area Below Reference Elevation (ft 2 ) Cross-section Area Below Reference Elevation (ft 2 ) Cross-section Area Below Reference Elevation (ft 2 ) Cross-section Area Below Reference Elevation (ft 2 ) Cross-section Area Below Reference Elevation (ft 2 ) Figure 6 continued. Cross-sectional Area Under a Datum 10,000 Larabee/Holmes Bar 11,400 South Fork Bar 9,500 11,300 9,000 11,200 8,500 11,100 8,000 11,000 7,500 10,900 7,000 10,800 11,000 Bowlby Bar 13,600 Vroman Bar 13,400 10,500 13,200 10,000 13,000 12,800 9,500 12,600 12,400 9,000 12,200 12,000 8,500 6,700 Maynard Bar 6,600 6,500 6,400 6,300 6,200 6,100 6,000 5, P a g e

20 Thalweg Elevation (ft) Maynard Vroman Bowlby South Fork Larabee (Holmes) Elinor Three Mile Dinner Creek Truck Shop Scotia Dam Net Change in Thalweg Elev (ft) Thalweg Elevation The channel thalweg is the deepest location in the channel. Increase in thalweg elevation indicates filling of the channel and a decrease indicates scouring. Since 1999, the thalweg adjacent to all of the bars except Three-mile has dropped in elevation (deepened). This is consistent with general scouring within the channel (Figure 5A). Deepening has been greatest in the upper reach and less in the vicinity of Scotia. Combining all cross-sections, there has been a net decrease in thalweg elevation (deepening) of about 1.0 feet since 2002 (Figure 7B). In the years from 1999 to 2003, there was considerable extraction of gravel within the reach and the thalweg elevation was shallower. After extraction decreased after 2004, the thalweg deepened by about 1 foot. Average thalweg elevation of each bar is shown in Figure 8. Figure 7. Net change in thalweg elevation averaged at the bar and reach scale. A). Net change in thalweg elevation from 1999 to 2008 for each bar. Bars are shown from left to right in order from upstream to downstream. B) Thalweg elevation of all bars within the Middle Reach of the Eel River averaged annually. A.) 1.0 Middle Reach of the Eel River Change Between 1999 and B.) Middle Reach of the Eel River Average all Gravel Bars P a g e

21 Average Thalweg Elevation (ft) Average Thalweg Elevation (ft) Average Thalweg Elevation (ft) Average Thalweg Elevation (ft) Average Thalweg Elevation (ft) Average Thalweg Elevation (ft) Figure 8. Thalweg elevation averaged by bar from 1999 to Scotia Bar 52 Truck Shop Bar Dinner Bar 57 Three Mile Bar Elinor Bar 97 Larabee/Holmes Bar P a g e

22 Average Thalweg Elevation (ft) Average Thalweg Elevation (ft) Average Thalweg Elevation (ft) Average Thalweg Elevation (ft) Figure 8 continued. Thalweg Elevation. 114 South Fork Bar 114 Bowlby Bar Vroman Bar 128 Maynard Bar P a g e

23 Elevation (ft) Mean Bed Elevation The mean bed elevation is calculated as the average of all cross-section points that within the width defined by the reference datum (see Figure 9). Cross-sectional area and mean bed elevation are calculated at the same reference datum. The channel thalweg is the deepest location in the channel. Increase in mean bed elevation indicates channel filling and a decrease indicates scouring. The change in mean bed elevation from 1999 to present is shown in Figure 10A and the average reach value is shown in Figure 10B. Figure 9. Definition sketch of mean depth calculation. Mean depth is the average elevation of the points under the reference elevation within the hatched area. 110 Dinner Cr Aug-07 Channel Elevation (ft) Reference Elevation For Calc Reference elevation Horizontal Distance (ft) General patterns in mean bed elevation do not follow those of thalweg elevation and cross-sectional area. Upper reach bars with significant deepening of the thalweg also tended to increase mean bed elevation. This indicates net bar building. There has been little net change in bed elevation in the middle bars despite deepening of the thalweg. Three-mile bar appears to be building at the expense of the adjacent Dinner Bar located just downstream. The lower bars had a small amount of thalweg deepening and a small increase in mean bed depth. Averaging all cross-sections through the reach indicates net increase in bed elevation since 2006 with little to no extraction each year (Figure 10B). The apparent dip in 2010 is a result of the methods problems in 2010 data. Mean bed elevation is shown for individual bars in Figure P a g e

24 Mean Bed Elevation (ft) Maynard Vroman Bowlby South Fork Larabee (Holmes) Elinor Three Mile Dinner Creek Truck Shop Scotia Dam Net Change in Mean Bed Elev (ft) Figure 10. Net change in mean channel elevation averaged at the bar and reach scale. A). Net change in mean channel elevation from 1999 to 2008 for each bar. Bars are shown from left to right in order from upstream to downstream. B) Mean channel elevation of all bars within the Middle Reach of the Eel River averaged annually. A) Middle Reach of the Eel River Change Between 1999 and 2011 B.) 92.0 Middle Reach of the Eel River Average all Gravel Bars P a g e

25 Average Bed Elevation (ft) Average Bed Elevation (ft) Average Bed Elevation (ft) Average Bed Elevation (ft) Average Bed Elevation (ft) Average Bed Elevation (ft) Figure 11. Mean bed elevation averaged for each gravel bar by year. 52 Scotia Bar 57 Truck Shop Bar Dinner Bar 64 Three Mile Bar Elinor Bar 101 Larabee/Holmes Bar P a g e

26 Average Bed Elevation (ft) Average Bed Elevation (ft) Average Bed Elevation (ft) Average Bed Elevation (ft) Figure 11. continued. Mean Bed Elevation 119 South Fork Bar 125 Bowlby Bar Vroman Bar 135 Maynard Bar Patterns in Bed Elevation in Relation to Extraction Volume Reach averaged thalweg and mean bed elevations are shown in relation to extraction volumes in Figures 12 and 13, respectively. There is a relationship between the average thalweg and bed elevations within the reach. As noted in HRC (2009), when extraction volumes are near the annual allowable, the thalweg elevation tended to increase (shallow) and the mean bed elevation tended to decrease (flatten). Conversely, when no extraction occurred, there was a decrease in the thalweg elevation (deepening) and an increase in the mean bed elevation (bar building). These results suggest that the bar surface is highest and the channel thalweg is deepest at low extraction volumes. Extraction shallows the thalweg and lowers the bar surface, which is included in the mean elevation calculation. The entire range of the effect on bed elevation between no extraction and maximum extraction is about 1 ft in both parameters. Note in the following figures that the bed elevations from the current year s survey is associated with the extraction volume the previous year. 26 P a g e

27 Mean Bed Elevation (ft) Thalweg Elevation (ft) The pattern in thalweg elevation continues to hold true in The average thalweg elevation scoured (Figure 12) and the mean bed elevation (Figure 13) was consistent with previous years with no extraction. Similarly, Figures 14 and 15 show the reach averaged thalweg depth and mean bed depth respectively. Note the data values from 2009 (2010 survey) are indicated by green triangles in the figures. This represents the 2010 data as submitted in the 2010 annual report, which requires correction. Both results are consistent with the data corrections described in the methods section. The 2010 survey data is not included in the regression calculations. The relationship of bed elevations in 2011 to annual reach extraction volume is consistent with previous years. In 2011, the reach-averaged thalweg was the deepest since Figure 12. Relationship between annual extraction volume and the average reach thalweg elevation for the Middle Reach of the Eel River. The 2011 data point is in red. The 2010 value is the triangle in green Middle Reach Eel River--Average All Bars y = 4E-06x R² = , , ,000 Annual Extraction Volume (Yd 3 ) Figure 13. Relationship between annual extraction volume and the average bed elevation for the Middle Reach of the Eel River. The 2011 data point is in red. The 2010 value is the triangle in green Middle Reach Eel River-- Average All Bars y = -7E-06x R² = , , ,000 Annual Extraction Volume (Yd 3 ) 27 P a g e

28 Mean Bed Depth (ft) Thalweg Depth (ft) Figure 14. Relationship between annual extraction volume and the average reach thalweg depth for the Middle Reach of the Eel River. The 2011 data value is in red. The 2010 value is the triangle in green Middle Reach Eel River--Average All Bars y = -4E-06x R² = , , ,000 Annual Extraction Volume (Yd 3 ) Figure 15. Relationship between annual extraction volume and the average bed depth for the Middle Reach of the Eel River. The 2011 data value is in red. The 2010 value is the triangle in green Middle Reach Eel River--Average All Bars y = 5E-06x R² = , , ,000 Annual Extraction Volume (Yd 3 ) Patterns Evident at Individual Bar Cross-sections In this section, we show a select group of cross-sections to illustrate patterns evident in individual crosssections that may provide insight into recent channel responses. Figure 16 shows two cross-sections on Scotia Bar and Figure 17 shows two cross-sections on Vroman Bar in the upper portion of the Middle Reach of the Eel River. Scotia Bar had decreased cross-sectional area, and increased mean and thalweg depth. Figure 16 suggests a general small amount of deposition across cross-section 1 while crosssection 2 has been more actively depositing with clear evident of bar building. Vroman Bar in the upper portion of the reach has had a large net increase in thalweg depth (decrease in thalweg elevation), and increase in cross-sectional area indicating net scour. These statistics appear to reflect general bar building going on at the site. What is clear in the cross-sections is that there is not general scour occurring. Gravels are generally accruing on the surface of the bar, and the portion of the bar within the most active portion of the channel under the 35% flow exceedance level is carved away or in some cases the thalweg deepens. In cross-section B, the area of extraction is evident and has filled in recent years. 28 P a g e

29 Elevation (ft) Elevation (ft) Figure 16. Scotia Bar cross-sections 1 and Scotia Dam Bar Cross-section Horizontal Distance (ft) HY2001 HY2002 HY2003 HY2004 HY2004 Ref Elev 35% Flow HY2005 HY2006 HY2007 HY2008 HY2009 HY2010 HY Scotia Dam Bar Cross-section Horizontal Distance (ft) HY1999 HY2001 HY2002 HY2003 HY2004 Ref Elev 35% Flow HY2005 HY2006 HY2007 HY2008 HY2009 HY2010 HY P a g e

30 Elevation (ft) Elevation (ft) Figure 17. Cross-sections on Vroman Bar plotted by year. The bright green and red lines with symbols represent 2009 and 2010 respectively. 155 Vroman Bar Cross-section A HY1999 HY2001 HY2002 HY2003 HY2004 Ref Elev 35% Flow HY2005 HY2006 HY2007 HY2008 HY2009 HY2010 HY Horizontal Distance (ft) 170 Vroman Bar Cross-section B HY1999 HY2001 HY2002 HY2003 HY2004 Ref Elev 35% Flow HY2005 HY2006 HY2007 HY2008 HY2009 HY2010 HY Horizontal Distance (ft) 30 P a g e

31 HABITAT MONITORING There is a biological monitoring project intended to complement the physical channel monitoring. The channel morphology in the Middle Reach of the Eel River is characterized for suitability as fish habitat. Three principal habitat types are identified, including pools, flatwater, and riffles, as described by the California Department of Fish and Game (Flosi et al. 1994). We add the alcove habitat type that usually is found as secondary channels along the river margin. Habitats are identified and mapped at each gravel bar extending a minimum of one half of a river meander sequence above and below a given extraction site. Additionally, a detailed habitat map delineates the more specific micro-habitat features based upon relevant life history stages of concern for each reach. Habitat units are recorded on the current aerial photographs for the reach. Depth and area of individual habitat units, the extent and type of cover available, and any additional observations (e.g., cold water seeps, undercut banks, etc.) are recorded. Annual habitat data submissions include the aerial photographs with the habitat units clearly delineated, summary tables including descriptions of the proportional area of each habitat types, the distribution of habitat measurements, and a narrative of habitat conditions. This type of habitat mapping has a significant element of subjectivity. Personnel conducting the monitoring coordinate with NMFS staff to try to ensure that methods are consistent among observers and meet the intent of the biological monitoring. Methods Biological monitoring survey methods were applied at each gravel bar permitted by HRC for collection of two fundamental categories of information: Physical habitat data covering distribution and characteristics of the three basic habitat types as described by the California Department of Fish and Game (Flosi et al. 1998): pools, flat water, and riffles. Habitat mapping of specific salmonid microhabitats within the macro-habitat types (adult holding, spawning, juvenile rearing. Alcoves were mapped and numbered as a micro-habitat unit because they were located away from the channel thalweg. Macro-habitat Habitat Surveys Macro-habitat units primarily represent geomorphic channel structure including pools, riffles, flatwater, and secondary channels. These units were readily discernable in the field without velocity measurement. The total stream length of the channel is classified into these habitat units. Characteristics measured for each macro-unit included average width, average depth, and maximum depth. For pools, the residual pool depth was calculated as the maximum depth minus the depth measured at the pool tail crest. Width of the unit was determined by GIS analysis of the low-level aerial photographs that were taken in July Depths were measured in the field at three locations selected by the surveyor and averaged. The maximum depth of pools too deep to wade was measured from a kayak with a sounding line; shallower areas were measured with a stadia rod. Data recorded at each macro-habitat unit followed Flosi (1984) and included: Unit type Mean length, Mean width Maximum depth 31 P a g e

32 Mean depth Pool tail crest depth Shelter rating Substrate Canopy cover Bank composition/vegetation Survey effort applied to each gravel bar covered a reach that generally extended at least one-half of a meander sequence above and below the gravel bar. However, many of the company-permitted bars are spaced sufficiently close that there was overlap of the survey reaches associated with each individual bar. Where survey reaches overlapped, the unit was associated with the nearest gravel bar. Channel macrohabitat units are not mapped between widely separated bars. Micro-habitat Surveys The objective of the micro-habitat mapping is to identify specific microhabitat features within the larger scale geomorphic channel structure that are likely used by salmonids. Micro-habitats consist of locations within or immediately adjacent to the wetted channel that provide adult holding (AH), juvenile rearing (2+ - up to 2+ years in the case of steelhead or coho represents the average smoltification age for these species ), spawning (SP), and alcove (AL) habitats, which may provide refuge during higher flows. Identification of the micro-habitats was based on general criteria developed from review of published literature (e.g. Barnhart, 1986, Bjorn and Reiser, 1991, McMahon and Hartman, 1989, Nickelson, et al., 1992) with added input from company fishery biologists and technicians that included insight based on observations of fish, substrate characteristics, and spawning activity (in the form of old redds) within this reach of the river. Biologically-defined micro-habitats are a subset of the total area of the stream. The mapping procedure required the survey crew to: Identify individual salmonid fish microhabitats based on stages of their life history, Determine the area extent of such habitat, Plot the habitat in the form of polygons on the appropriate aerial photograph covering each gravel bar and immediate vicinity. Original field data for habitat assessment is provided in Appendix A. Aerial Photography, Mapping and GIS Processing An aerial photograph of the Humboldt Redwood Company s extractable gravel bars were provided from Streamline Planning. Air photos were flown in July These images, in conjunction with GPS, became the foundation for the salmonid habitat mapping. These the geo-referenced aerial photographs are referred to photo maps in this report. The field habitat survey was completed in 2 phases. The first phase focused on the macro-habitat unit delineation (pool/riffle/flatwater). The location of each macro-habitat unit was established at the channel thalweg using a coordinates collected with a hand held GPS unit. The coordinates of these points were entered into GIS to mark the upstream and downstream ends of each macro-habitat unit. Each macro-unit was uniquely numbered sequentially beginning at the most downstream point. A total of 69 macro- 32 P a g e

33 habitat units were mapped this year, 12 fewer units then were mapped in A total of 16 units were eliminated and 4 units were added. Elimination of units occurred mostly due to the classification change of flatwater designations in a riffle-flatwater-riffle sequence. To maintain numbering sequences, removed numbering units were skipped, and the 4 additional units were given a.1 designation similar to microunits. These added units included 13.1, 34.1, 74.1, and The thalweg of each macro-habitat unit is traced onto the photograph, color-coded by habitat type (Figure 18). Table 4 lists the gravel bars and macro habitat units covered by each photo maps. The length of each macro-unit was determined as the horizontal distance between the downstream and upstream coordinates of the unit using the Calculate Geometry feature of the length field in ARCMAP. The wetted width of the channel was determined by using the measure tool of ARC Desktop. Table 4. Coverage of aerial photos in submittal package. Photo # Photo Contains Bars: Photo Contains Macro-units: 1 --Scotia Bar --Lower portion of Truck Shop Bar 2 --Truck Shop Bar --Dinner Creek Bar Three Mile Bar Elinor Bar Elinor Bar Holmes/Larabee Bar Holmes/Larabee Bar South Fork Bar Bowlby Bar 9 --South Fork Bar Bowlby Bar 10 --Vroman Bar Maynard Bar The photomaps were taken to the field to complete the micro-habitat mapping. The micro-habitats are shown on the photo using codes reflecting the relevant salmonid life history stage: AH for adult holding, 2+ for juvenile rearing, SP for spawning. Alcoves, an over-wintering habitat, were treated as microhabitats because they are located on the site of the channel and not along the thalweg. There are referenced as AL on the photographs and data sheets. Each micro-habitat polygon was plotted on the field copy of the orthophoto. The micro-units are numbered as a subset of their associated macro-unit. For example, a micro-habitats located within or adjacent to macro-unit 12 is numbered 12.1, 12.2 and so on. This numbering convention was adopted in 2011 to facilitate comparison of micro-habitat location and area from year to year. The area of the micro-habitats was calculated using the Calculate Geometry function in ARC Desktop. The maps contain additional information, including the monitoring crosssections and the maximum and pool tail crest measurement at the location of measurement. The numbering convention of the cross-sections matches the submittals of cross-section data. Data on their location was provided from the surveyors in the State Plane Coordinate system. The HRC GIS department used the Table to Feature tool in ARC Catalogue to create the points and arcs of the crosssections, then projected them into the ALBERS projected coordinate system. 33 P a g e

34 Figure 18. Example photo map created by HRC GIS department of gravel bar and habitat features. 34 P a g e

35 Results Habitat Mapping Channel Units were surveyed from September 26 to September 28, The Scotia gage indicated flow of 119 cfs (9.04 ). Macro-Habitat Channel Unit Distribution The total length of main channel surveyed in 2011 was 82,380 feet (Table 5). The proportion of the three main habitat units was 49% pools, 22% riffles, and 29% flatwater. Absolute unit lengths and associated proportions of macro-habitats mapped were similar to that measured in Table 5. Distribution of macro-habitat lengths in the Middle Reach Eel River. Total Length (ft) Pools Riffles Flatwater Total # of Units % of Length Total Length (ft) # of Units % of Length Total Length (ft) # of Units % of Length Total Length (ft) % of Length % 13, % 27, % 76, , % 17, % 29, % 81, , % 17, % 22, % 83, , % 19, % 23, % 83, , % 17, % 24, % 82, The characteristics of individual macro-habitat units measured in 2011 are provided in Table 6.These include substrate and cover ratings of the micro-habitats. 35 P a g e

36 Table 6. Macro-habitat unit characteristics measured in Reach Unit # Scotia Truck Shop Elinor Macro-Habitat Units Macro Unit Length Habitat type (ft) Unit Area (ft 2 ) Micro-Habitat Units Substrate Cover Microhab.# Micro Habitat Type Micro Habitat Area (ft 2 ) Dominant Substrate Codominant Substrate Dominant Cover Codominant Cover Shelter Rating 1 Pool Gravel Bedrock Bedrock ledge LWD AH 1.2 AH 2 Riffle Gravel Sm Cobble Bubble Curtain Bedrock ledge AL Gravel boulders Boulders Terr Veg Flatw ater Gravel Sand Aq veg Boulders AH 4 Pool Sand Gravel Bedrock ledges Aq veg AH 4.2 AH 5 Flatw ater Gravel Sm. Cobble Bubble Curtain Boulders AH 6 Riffle Gravel Sm. Cobble Bubble Curtain Boulders % Coverage 6.2 AL Gravel Boulders Boulders Aq veg Flatw ater Gravel Boulders Terr veg Boulders AH 8 Riffle Gravel Sm Cobble Bubble Curtain Aq Veg AL Gravel Sand Terr Veg Aq Veg Flatw ater Gravel Sm. Cobble Boulders Aq Veg Pool Gravel Lg. Cobble Boulders Aq Veg AH 11 Riffle Gravel Sm.Cobble Bubble Curtain Boulders AL Sm Cobble Gravel Boulders Aq Veg Flatw ater Sand Gravel Boulders Aq Veg AH 12.2 AL Gravel Sand Terr Veg Aq Veg AL Gravel Sand Terr Veg Aq Veg Riffle Gravel Sm. Cobble Aqua Veg Terr Veg Flatw ater Gravel Sm. Cobble Terr Veg Aq Veg Riffle Gravel Sm. Cobble Bubble Curtain Undercut bank AL Gravel Sm. Cobble Terr veg Aq veg Flatw ater Gravel Sand Undercut bank Bubble Curtain Riffle Gravel Boulders Boulders Aq Veg Flatw ater Gravel Sm Cobble Boulders Bubble Curtain Riffle Gravel Boulder Bubble Curtain Boulders Pool Sand Gravel Aqua Veg Boulders AH 20 Riffle Gravel Sm. Cobble Bubble Curtain Terr Veg AL Gravel Sand Aq Veg Terr Veg SP 21 Pool Gravel Sand Bedrock ledges Aq Veg AH 21.2 AH 21.3 AL 22 Pool Sand Gravel Boulders Terr Veg AH 23 Flatw ater Sand Gravel Boulder Large Cobble Riffle Gravel Sm. Cobble Boulder Gravel Flatw ater Gravel Sm. Cobble Bubble Curtain Undercut bank Riffle Gravel Sm Cobble Bubble Curtain Terr Veg Pool Sand Gravel Aq Veg Bedrock ledges AH 27.2 AL Sand Boulder Aq Veg LWD Riffle Sm. Cobble Lg. Cobble Boulders Bubble Curtain Flatw ater Gravel Sm. Cobble Aq Veg Terr Veg Riffle Gravel Sm. Cobble Bubble Curtain LWD Flatw ater Gravel Sm Cobble Terr Veg LWD AH 32 Riffle Gravel Sand Bedrock Boulder AL Gravel Sm. Cobble Aq Terr SWD Flatwater Sand Gravel Bedrock ledges LWD AH 34.1 Riffle Gravel Sand Boulder LWD Pool Sand Gravel Bedrock ledges Aq Veg AH 35 Flatw ater Gravel Sand Aq Veg LWD P a g e