BANK STABILITY and EROSION ASSESSMENT Public Utility District No

APPENDIX E.6.2

TECHNICAL MEMORANDUM FOR BANK STABILITY AND EROSION ASSESSMENT Public Utility District No. 1 of Okanogan County Final License Application

APPENDIX E.6.2

TECHNICAL MEMORANDUM FOR BANK STABILITY AND EROSION ASSESSMENT

1.0 INTRODUCTION This Bank Stability and Erosion Assessment was undertaken on behalf of the Okanogan Public Utilities District in support of their relicensing application for the Enloe Hydroelectric Project being prepared under Federal Power Act 18CFR, Subpart E, Section 4.41. This assessment was conducted in conjunction with the related study: Pool Hydraulics, Sediment Balance and Sediment Transport Study, both of which are being used to help develop the Erosion and Sediment Control Plan that will address site-specific mitigation measures to minimize erosion and sedimentation effects during the construction, repair and operation of the dam and facilities.

2.0 OBJECTIVES The purpose of the Bank Stability and Erosion Assessment was twofold:

1) to identify major and minor erosional and depositional features upstream and downstream of the Enloe Dam that may affect sediment transfer processes and fish habitat in the Similkameen River, and

2) to assess the effect of future construction and operational activities associated with Enloe Dam on channel and bank stability, sediment transport mechanisms, and impoundment characteristics.

The study area encompasses the region of the Similkameen River from just downstream of the village of Nighthawk to the area south of Oroville, at the confluence with the Okanogan River. The section of the river studied measures approximately 12 miles in length.

3.0 PHYSICAL SETTING Enloe Dam is located on the Similkameen River 8.8 miles upstream from its confluence with the Okanogan River in Oroville in north central Washington. About 90% of the 3,592 mi2 basin is in British Columbia, as it drains the eastern side of the Cascades in

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 1 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

Washington and British Columbia and the Thompson (or Interior) Plateau of British Columbia. The river is fed by three main tributaries, which include the Pasayten River near Manning Park, BC (most of which is in northern Washington), the Tulameen River at Princeton, BC and the Ashnola River near Keremos, BC. Downstream of the international border (at Chopaka), the Similkameen River receives almost all of its incremental flow within Washington from the Palmer Lake/Sinlahekin Creek watershed (Figure 1).

Much of the watershed is rugged with high relief, especially along the southern and western boundaries, where elevations range upwards from 7,000 to 8,600 feet above mean sea level (amsl) along the western divide. The major river valley bottoms range from about 2,300 feet amsl at Princeton, BC to 900 feet amsl at Oroville. From Princeton, BC to Palmer Lake, WA (at 1,160 feet), the Similkameen River valley is in a predominately wide, flat-bottomed, low-gradient (dropping approximately 1.5 feet per thousand feet) U-shaped valley reflecting geologically recent glaciation. Downstream of Palmer Lake the river takes an abrupt northward turn into a narrow, steep valley that descends at a gradient of about 2.4 feet per thousand to Shanker’s Bend at the upstream end of the Enloe impoundment. At this point the river channel turns southeast towards Enloe Dam and onwards to Oroville. Prior to dam construction the river channel narrowed and steepened considerably to a gradient of approximately 7 feet per thousand (including the drop over Similkameen Falls). As a consequence, the resulting impoundment is very narrow, long and sinuous. Below Similkameen Falls the river descends at a gradient of about 2.8 feet per thousand feet over the lower 8.7 river miles into Oroville.

4.0 STUDY METHODS This study was undertaken in two tasks:

• Task 1) Air photo interpretation, and

• Task 2) Field reconnaissance.

AIR PHOTO ANALYSES Two sets of aerial photographs, (1953 from the USGS) and 2000 (from WSDOT) were obtained to identify major and minor upland sediment sources, characterize river and channel characteristics, and to document hillslope and fluvial geomorphic changes that had occurred in the study area over the 47 year period. Geomorphic changes over time were assessed by comparing upland sediment sources (erosional landscape features such as badlands, gullies, landslides and other mass wasting landforms) and riverine channel characteristics and depositional features (such as bars, banks, terraces and benches) in the two sets of photos.

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 2 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

The following sets of aerial photographs were used in the study:

• USGS July 2, 1953 1:37,400 scale (1 inch ~ 3120 feet)

• WSDOT July 29, 2000 1:12,000 scale (1 inch ~ 1000 feet)

These features which were determined to be a potential source of sediment in the Similkameen River are presented on Figures 2A through 2D.

FIELD RECONNAISSANCE The objectives of the field reconnaissance were to document conditions of the channel, streambanks, and valley walls and qualitatively evaluate potential sediment sources and sinks as they would relate to sediment accumulation rates in the Enloe impoundment, and the effects on erosion and sediment processes (e.g., bar formation or denudation) downstream of the Enloe Dam.

With these objectives in mind, a field reconnaissance of the Similkameen River channel up and downstream of the Enloe Dam was conducted from September 25 – 27, 2006. The river downstream from the dam to Oroville was rafted on September 25, while the river upstream of the dam from approximately river mile 13.5 to the forebay area (at RM 8.9) was rafted on September 26. A vehicle reconnaissance of the lower watershed (from Oroville to Nighthawk) was conducted on September 27.

During the recons, observation stations were determined based on unique river reach or valley character. At each observation station channel and bank characteristics were described and conditions were photo-documented on both the raft and vehicle recons. Raft-recon and vehicle-recon station descriptions with photo references are included as Tables 1 and 2 (at end of this section), respectively. Locations where field observations were made are also plotted on Figures 2A to 2D.

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 3 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

This page is left intentionally blank.

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 4 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

[ App E.6.2 Figure 1 Similkameen River Watershed ]

[ App E.6.2 Figure 2A ]

[ App E.6.2 Figure 2B ]

[ App E.6.2 Figure 2C ]

[ App E.6.2 Figure 2D ]

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 5 August 2008 Okanogan County

~e l owna Central Okanagan Regional District

Ctiugla County Grant L1ncolri County County ·

Legend • Cit y USGS Stream Ga ge on S1.milkameen River

Major River

Fraser Valley Regional Canadian Division and Count y District Koote~ay Boundary Regional District US County

CANADA USA roville s 0 2.5 5 10 D Miles ata sources : BC WAT ERSH E Washington Dept of ED Al T LAS SOK, Whatcom · co ogy County

Okanogan Enloe Da m L"icensmg . Project County Tonasket Figure 1 Similkameen R"1ver Watershed Skagit County EN TRIX

T: \ :"l h "- r e g i :"l\gi !In t\enlo!'!\ 4 1 2 9 501_ En l o e Da m \ ma p \ f'LA\ Enl oe_Wate r:oi h e d _ l 7 i l l i _ Ol. m:xd 5/5/08 Okanogan County

Do ugld County Lincoln , i:~r anl Courtty Cou11ty

Legend

En loe Dam

Badlands/ La ndslides

Gull ies/ Streambeds (wet or dry)

Pointbars/ Sidebars/Mid-channel Ba rs

Pointbars/ Sidebars/Mid-channel Ba rs (submerged) * Bank Stabil it y Assessment Point ( Raft )

* Bank Stabil it y Assessment Point (Veh icle)

River Mile (RM)

,-._'~·· Approximate Stream Channel - 1953

W E

500 0 500 1,000 --=::::::m--c::==:::::i Feet Image sources : 2005 USDA National Agricultu re I magery Program Data sources : Was hington DNR, Okan ogan Cou nt y

Enloe Dam Licensing Project Figure 2A Similkameen River Upland Sediment Sources and Geomorphic Features EN TRIX

T: \ !!h are gi!l\gi ~n t\ e nlo e \ 412 9501_Enlo eDa m\ map\f'LA\ Enloe _ Ge omo r p h _17i l l i_O 2 . mxd 5 / 2 1 / 0 8 .. Okanogan County

Do ugld County Lincoln , i:~r anl Courtty Cou11ty

Legend

En loe Dam

Badlands/ Landslides

Gull ies/ Strea mbeds (wet or dry)

Pointbars/ Sidebars/Mid-channel Ba rs

Pointbars/ Sidebars/Mid-channel Ba rs (submerged) * Bank Stabil it y Assessment Point (Raft) * Bank Stabil ity Assessment Point (Vehicle) 0 River Mile (RM )

,-,'~·· Approximate Stream Channel - 1953 t FERC Boundary

500 0 500 1,000 --=::::::m--c::==:::::i Feet 8 I mage sources: 2005 USDA National Agricultu re I magery Program Data sources : Was hington DNR, Okan ogan Count y

Enloe Dam Licensing Project Figure 2B Similkameen River Upland Sediment Sources and Downstream Geomorphic Features F~C Bound~ry______..::,__, EN TRIX

T: \ !!he.re gi!l\gi!In t\e nlo e \ 412 9501_EnloeDe.m\ map\f'LA\ Enloe _ Ge omo r p h _17i lli_O2 . mxd 5 / 2 1 / 0 8 Okanogan County

Do ugld County Lincoln , i:~r anl Courtty Cou11ty

Legend

En loe Dam

Badlands/ La ndslides

Gull ies/ Streambeds (wet or dry)

Pointbars/ Sidebars/Mid-channel Ba rs

Pointbars/ Sidebars/Mid-channel Ba rs (submerged) * Bank Stabil it y Assessment Point ( Raft ) * Bank Stabil it y Assessment Point (Veh icle) River Mile (RM)

Approximate Stream Channel - 1953

500 0 500 1,000 --=::::::m--c::==:::::i Feet Image sources : 2005 USDA National Agricultu re I magery Program Data sources : Was hington DNR, Okan ogan Cou nt y

Enloe Dam Licensing Project Figure 2C Similkameen River Upland Sediment Sources and Geomorphic Features EN TRIX

T: \ !!h e.re gi!l\gi!In t\e nlo e \ 412 9501_Enlo eDe.m\ map\f'LA\ Enloe _ Ge omo r p h _17i l l i_O 2 . mxd 5 / 2 1 / 0 8 Okanogan County

Do ugld County Lincoln , i:~r anl Courtty Cou11ty

En loe Dam

Badlands/ La ndslides

Gull ies/ Streambeds (wet or dry)

Pointbars/ Sidebars/Mid-channel Ba rs

Pointbars/ Sidebars/Mid-channel Ba rs (submerged) * Bank Stabil it y Assessment Point ( Raft ) * Bank Stabil it y Assessment Point (Veh icle) River Mile (RM)

Approximate Stream Channel - 1953

500 0 500 1,000 \ --=::::::m--c::==:::::i Feet I Image sources : 2005 USDA National I I I I I I Agricultu re I magery Program I I Data sources : Was hington DNR, Okan ogan Cou nt y iI /1I I Enloe Dam Licensing Project ! Figure 20 Similkameen River Upland Sediment Sources and Geomorphic Features EN TRIX

T: \ !!h are gi!l\gi ~n t\ e nlo e \ 412 9501_Enlo eDa m\ map\f'LA\ Enloe _ Ge omo r p h _17i l l i_O 2 . mxd 5 / 2 1 / 0 8 Public Utility District No. 1 of Okanogan County Final License Application

5.0 RESULTS

AIR PHOTO ANALYSES Historical daily mean streamflow was obtained from USGS’s Nighthawk station (USGS station 12442500). Streamflow data reports that the July 2, 1953 daily mean flow was 6770 cfs, while the July 29, 2000 daily mean flow was 1360 cfs. This difference indicates that more channel substrate was exposed in the 2000 photos, so that any observed increase in size of various channel morphologic features (i.e., point bars, side bars) may be due to reduced streamflow and not to an increase of sediment deposited.

Identified upland sediment sources are presented on Figures 2A – 2D. The features presented represent geomorphic features that are probable or possible sources of sediment to the Similkameen River. These features include badlands, gullies, and landslides, and are designated as S1 through S40. Areas of sediment in the form of point bars, side bars, and mid-channel bars are also presented on Figures 2A – 2D.

The Badland features identified contain steep slopes and gullies, loose soil, and frequent erosion. Features identified as gullies are gentler in topography compared to the badland features, contain varying amounts of vegetation, and often contain streambeds (wet or dry). Landslides noted resemble talus or scree slopes.

Nighthawk Area and Downstream (Figure 2A) (River Mile 17.0 to 13.5)

Downstream of Nighthawk (the furthest upstream portion of the study area at River Mile 17), no upland sediment sources are noted in the area. The stream channel does not contain evidence of point bars, side bars, or mid channel bars. Topography adjacent to the River consists of agricultural landscape surrounded by elevated treeless ridges on either side. These topographical features and the channel descriptions were unchanged from 1953 to 2000.

Figure 2A presents 14 potential sediment sources to the Similkameen River. These features consist of badlands, gullies (and/or streambeds) (S1 – S14). Two of these identified features suggest evidence of sediment contribution to the river. These features are described below.

Moving downstream of River Mile 16, a shallow gully containing a dry streambed (S3) is noted upland (Figure 2A). In the 1953 photo, there is evidence that this gully introduced sediment into the Similkameen River. A sidebar is present in the stream channel at the base of this feature. In the 2000 photo, a canal or other narrow body of water is present in the area, between the gully and the Similkameen River. Sediment appears to be impacting this narrow body of water in the 2000 photo. Approximately 1000 feet downstream from this historical sediment source a point bar is present during both time periods.

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 15 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

Approximately one mile downstream at River Mile 14.5, a sparsely vegetated badland (S11) is present in this area. Sidebars are present on both stream banks indicating that sediment is deposited into the river from this feature; however the presence of the roadway may inhibit the majority of the sediment contribution to the river. About 1000 to 2000 feet downstream of this feature, two mid-channel bars are present in the 2000 photo (but not in 1953). Channel characteristics generally were unchanged from 1953 to 2000.

Upstream of Shanker’s Bend to Dam (Figure 2B) (River Mile 13.5 to 9.0)

General topography upstream of the dam is gently rolling to steeply sloping on each side of the river. Steeper areas contain gullies or badland features. Upland areas are generally covered with brush vegetation and few trees. In the stream channel, small point bars and sediment bars are common in certain sections and appear to contain both, fine or coarse material, while stream banks generally contain a conglomeration of fine-grained material, cobbles and boulders. Field observations indicate that much of the river bottom consists of cobbles and boulders or exposed bedrock.

According to the literature reviewed, the stream bottom upstream of the reservoir consists largely of cobbles and boulders with some gravel and little sand (Nelson, 1972). It was reported that very little sediment was deposited on the banks or in the channel upstream of the reservoir (Nelson, 1972). The description is consistent with observations made during the field reconnaissance described below and summarized in Table 1.

Compared with the section downstream of Nighthawk, increased badlands and potential sediment sources are present over the stretch of river from Stations T through AB. Identified sediment sources that indicate evidence of sediment contribution to the river are described below.

A badland feature (S16) is present near station U, and a small sidebar is present in the river at the base of the badland. A larger sidebar is present at station Y; the source of the sediment present in this area is likely the gully and streambed present upland of the sidebar to the south (S19). Numerous badlands are present on the opposite (northern) bank, however the geomorphic patterns on the photos suggest that these badlands do not impact the river (S20), and the sediment eroded from the badland is deposited somewhere upslope. Near station AA, a badland feature is present that does appear to deliver sediment to the river (S23). On the opposite (southern) bank, a point bar (portions of which were submerged in both photos) is present. These features noted are present in both the 1953 and 2000 aerial photos.

Just downstream of the upstream FERC boundary (Figure 2B, station AF), several minor sediment sources (one small landslide (S26) and one small gully (S27)) and one major sediment source (badland) (S29) are present upland of Shanker’s Bend. Sidebars

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 16 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

are present in the River at each of these areas indicating the contribution of sediment from these sources. Features noted are present in both the 1953 and 2000 aerial photos.

Approximately 500 feet upstream of the dam, a submerged point bar is present in both 1953 and 2000 photos. Another potential upland sediment source (gully at S32) is present in this area, however, the presence of the point bar is likely due to the erosion of the stream channel and the opposite stream bank. Although the point bar is not visible in the 1953 photo (which is likely due to the angle of the photography), surrounding features and topography have not changed, indicating that the point bar was likely present below the water surface in 1953.

A talus slope at the base of a cliff (S33), a potential sediment source to the river, is present upland to the east of the river.

Downstream of Dam (Figures 2B & 2C) (River Mile 9.0 to 5.0)

Topography downstream of the dam is steeply sloping on each side of the river with little vegetation present. Exposed soil and sediment ranges in size from fine material to large boulders. The area is primarily vegetated with grasses and sage, and there are few exposed areas (i.e., no large badlands). Large bedrock outcrops are common and are exposed in the upland and within the lower valley areas. Talus or scree slopes are evident along streambanks. Field observations indicate that much of the river bottom consists of cobbles and boulders or exposed bedrock. Areas of fine sediment material appear to be limited, and may occur only in the few areas where point bars or sidebars are present.

Just downstream of the dam (within 200 feet), a steep gully and small stream is present (S34). Field observations indicate that the river bottom just downstream of the dam cuts into bedrock and contains little fine sediment material.

From 1500 to 3000 feet downstream of the FERC boundary (stations D - F), one gully (S35) and two minor landslides (S36 and S37) are present that likely contribute sediment to the River. Two sidebars just downstream of these sources are present as well as a mid-channel bar. The features noted are present in both the 1953 and 2000 aerial photos.

Near station I, several upland partially to fully vegetated gullies are present (S38). These gullies are likely a minor source of sediment, as point bars lie just downstream of the gully mouths in the area. The features noted are present in both the 1953 and 2000 aerial photos.

Midway between stations M and N, a landslide is present on the southern bank of the river (S40) that is likely a source of sediment indicated by the sidebar located downstream. This feature is present in both the 1953 and 2000 aerial photos.

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 17 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

At station O, a sidebar is present, however no obvious sediment sources are located in the area. Surrounding topography beginning at Station O becomes comparatively gentler, compared to the steeper topography in the sections described above.

Oroville to Okanogan River (Figures 2C & 2D) (River Mile 5 – 2)

Downstream, from Oroville to the confluence of the Similkameen River with the Okanogan River, a meandering stream pattern is present on gentler terrain, in contrast to the steeper topography upstream. Numerous point bars and sidebars are present in the area. Oxbow lakes and historical stream channels are present in the surrounding area. A similar stream pattern is present south of the confluence of the two rivers.

Minor stream adjustments were noted when comparing the 1953 and 2000 photos. These stream channel adjustments are depicted on Figure 2D.

Additionally, the 2000 photos suggest that there appears to be a noticeable reduction in stream stage or water volume in the river in the vicinity of the City of Oroville (and likely downstream of the dam) when compared with the 1953 aerials. This is consistent with the significantly lower discharge measure in the river at this time.

FIELD RECONNAISSANCE During the period of field reconnaissance mean daily discharges (as measured at the USGS Nighthawk station) were 365, 349 and 333 cfs on September 25, 26 and 27, 2006, respectively. September typically has the lowest mean daily discharges. The 1928-2006 mean daily flow for September is 592 cfs, while a flow of 350 cfs in September is exceeded about 80% of the time. Mean daily flows are generally low from August through March, ranging up to 910 cfs, and increase substantially during the spring runoff period beginning in April and peaking in May (7,830 cfs) or June (8,570 cfs). Thus, the field reconnaissance was conducted during exceptionally low flow conditions (especially when compared to the higher stage characteristics of the river shown in the air photos), where much of the channel substrate and banks were exposed.

Observations of channel and bank conditions, and potential sediment sources and sinks are summarized for three main reaches that include: 1) upstream of the impoundment, 2) impoundment, and 3) downstream of impoundment. Detailed descriptions and representative photos and location references of:

• badlands and/or landslides;

• gullies;

• erosional scars along streambanks;

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 18 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

• alluvial fans, talus cones or aprons composed of rock, gravel and/or sand;

• sand, gravel, cobble-boulder river bars; and

• general channel, streambank and valley conditions;

are compiled in Tables 1 and 2 by field observation station. Station locations are plotted on Figures 2A to 2D. A photolog is included as Attachment A.

Upstream of Impoundment At Nighthawk and downstream from Palmer Lake, the Similkameen River flows northward and its channel begins to narrow and steepen and become less sinuous and more incised into the surrounding valley (Photos V042-V046 – see Attachment A), with an average channel gradient of about 3 feet per thousand up to Shanker’s Bend (located near the upstream limit of the Enloe impoundment at Station AG).

Along the narrow valley section downstream of Palmer Lake and upstream of the Enloe impoundment, the uplands are composed primarily of metasedimentary and metavolcanic rocks, interspersed with metavolcanic, intrusive (dacite), and sedimentary rocks (conglomerate). Much of the valley and sideslopes, however, are mantled in Quaternary glacial drift, which is in places exposed by extensive gully systems or badlands (Photos V037, P054, P081 and P089).

In the upper reaches from the USGS Nighthawk gaging station (located on LB in distant center of Photo V044) to Station S, the river has a relatively gentle channel gradient with numerous riffle-pool-glide sequences, and stable gently sloping vegetated banks within a moderately sloping valley (Photos V038, V042, V044, P051 and P052). The channel substrate is comprised of primarily cobbles and gravels (in upper reaches) changing to cobbles and boulders, sometimes with bedrock (Photos V040, P054-P056). In numerous locations bedrock extends across the entire channel (Photo V031)

Relatively uniform channel widths and depths in the upper reaches (from Nighthawk to Station S) change to highly variable widths in the lower section (station T to station AG), although in general width to depth ratios are high (>100:1) (Photos P054, P062, P067, P069, P078, P090 and P092). The changes in width are associated with sometimes steep to vertical bedrock cliffs (Photos P065-P070) or steep colluvial slopes (Photos P053, P085-P087) along one bank to extensive cobble-boulder bars along the other bank (Photo V032) as observed in the vicinity of Stations AA, AB and AC. The lower reach is dominated by long riffle-glide-pool sequences where the pools are typically deep and formed within a bedrock-dominated channel (Photo V033).

Small isolated sand bars occur at Stations S, Y and Z and in general throughout the section (Photos P051, P077 and P078), but coarser large cobble-boulder bars are predominant, such as at Stations Y and AA (P071, P074, P075 and P082). There is

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 19 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

very little fine-grained sediment in the channel or along the banks. Fine-grained sediment sources, where available, originates from primarily colluvium that has been cut at high flows along the channel margins, or from the few gullies that drain large badland features located upslope of either the road to the north side or the old railroad line to the south at Stations U and V (Photos P057-059 and P063). Erosional scars and talus aprons (from cuts and fills) associated with the old railroad line are numerous along a bench that sits from about 15-50 feet above and along the right bank (Photos P034, P040 and P061). Although numerous, these cuts do not appear to provide a significant source of sediment to the river, as they are relatively small located on an elevated bench and are not in direct contact with the river channel.

Overall, within this upper section, zones of fine-grained sedimentation are scattered and generally small in size and volume. Tributary sources are minimal and limted to a few gullies. Coarser material (cobbles and boulders) are abundant, and the channel morphology is influenced most by its level of incision into the glacial overburden and/or bedrock.

Impoundment Just upstream of Shanker’s Bend, the river flows into the Enloe impoundment (Photos V019, V020, V024, V025 and V027) at Station AG, and the reservoir turns and snakes southeastwardly through the valley to the dam (Photos V028-V030). Prior to dam construction the river channel narrowed and steepened considerably to a gradient of more than 8 feet per thousand (including the drop over Similkameen Falls at the dam location). As a consequence, the resulting impoundment is very narrow, long and sinuous and is surrounded by moderately steep valley walls composed of vegetated to partially vegetated colluvium or exposed bedrock (Photo P111).

The upper reservoir is characterized more by vertical bedrock cliffs and steep colliuvium-mantled bedrock walls (at Stations AG and AH), while the lower reservoir is set in a more open area surrounded by moderately steep valley walls (at Stations AI- AK). A long belt of partially vegetated road-fill colluvium is present for approximately 500 feet along the left bank in the upper reservoir (Photo P104), and a small gravel-cobble fan that drains an upland badland via culvert occurs at Shanker’s Bend (Photo P107) and culvert below road.

One large partially vegetated (mostly grasses) high sand bar is located along the RB just downstream of Shanker’s Bend (Photos V026, V027 P109 and P110). A number of small partially vegetated sand bars and benches are located at the base of near-vertical cliffs in the upstream reaches of the impoundment (Photos P102, P103, P106 and P108). These benches and the narrow benches located along the LB in the lower reservoir (Photo V019 and V020) are likely submerged during periods of high flow. Extensive erosional scars on a narrow bench occur along the RB and are associated with high water conditions (V022-V024, P112 and P115).

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 20 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

Channel width is relatively uniform throughout the reservoir and the reservoir substrate. (ripple morphology) in the shallow water zones is easily visible. Generally, from the upper to lower impoundment, the channel substrate is dominated by sands with scattered cobbles but changes from a cobbly sandy gravel (at AG) to a gravelly sandy (at AH) to primarily medium sand (at AI to AK).

Downstream of Impoundment Downstream of the dam, the river channel is relatively gentle with an average gradient of 1.4 feet per thousand over the lower 8.7 river miles into Oroville. The upper reach of this section (Stations A to K) is slightly steeper in locations (rapids) as it flows through a narrow canyon with steep to vertical walls (Photos V011, V014, P007, P011, P016 and P026). In the lower reach (Stations L to Q), the valley widens, and the valley walls and streambank heights are reduced (Photos V004 and V010). The lower river is shallowly incised within an extensive floodplain terrace that marks the confluence with the Okanogan River in the much broader Okanogan River valley (Photo V002).

Within the canyon, the channel substrate is comprised mainly of either bedrock and boulders (forming rapids) near Stations A, B, D, G and H (Photos P001, P007, P009, P015, P025, P028 and P029) with deep pools (> 10 feet) in many places at Stations A, C, H and I (Photos P003-P005, P011, P026, P029 and P030), or an extensive cobble- boulder substrate (Photos P017, P023 and P024). Steep to vertical canyon walls formed in bedrock are common along both right and left banks at Stations A, I, J and K (Photos P036-P039); these are interspersed with angular rock talus cones and/or aprons (Photos P030 and P032). Finer-grained colluvial aprons or fans shed from weathered and eroding foliated schistose meta-sedimentary rocks are less common (Station F: Photos P019, P021 and P023).

The channel is characterisitcally relatively narrow with small isolated sand bars located along the tops of bare to grassy banks at Stations H and J (Photos P027 and P035) and narrow boulder-cobble bars that armor both left and right banks (Photo P026). High water lines, marked on bedrock by a silt line (Photos P033 and P038), or by the grassy banks can be found throughout this section. One exceptionally large sand/cobble bar is located downstream of a mid/side-channel rock island at Station I (Photos P018, P031, P033 and P034).

Conditions change somewhat downstream of Station L and the old railroad crossing; the valley and channel widens, and the channel is cut into high terraces and lower floodplain (farmed) terraces (Photos P042 and P043). Much of the non-developed riparian zone is vegetated with mixed grasses and conifers (Photos P042, P044, P047 and P048). The channel substrate is predominantly cobbles with gravels and boulders in part and/or bedrock in a few places (Photos P042, P045 and P046). Banks are comprised of boulder-cobble armor or rip-rapped with boulders (Photos V001 and V004) – including an extensive diking system that protects the City of Oroville.

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 21 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

The right bank downstream of the railroad at Stations L and M is formed by a relatively high alluvial terrace, which has been cut by numerous landslip scars (Photos V005- V008 and P041). In some cases, the headscarps of these scars are unstable and enlarging upslope (Photo V008). The scars feed large unvegetated to partially vegetated talus cones or aprons comprised of sands and gravels. The cones/aprons are generally armored by cobbles and boulders (Photos V005, V006 and P046).

Adjacent to the City of Oroville and just upstream of the confluence at Station Q, the Similkameen River morphology changes somewhat, meandering more and occupying side channels and braids. The substrate at this point is primarily gravels and cobbles.

Overall, within this lower section, zones of fine-grained sediment sources are rare (except the landslip/badland cuts into the high alluvial terrace (around stations L and M) and there is in general few fine-grained sediment deposits. Tributary sources of sediment are essentially non-existent. Coarser material (cobbles and boulders) are abundant, and the channel is shaped primarily by bedrock.

6.0 CONCLUSIONS The air photo assessment indicated 40 upland sediment sources in the study area. These sources included badlands, gullies, streambeds (wet or dry), and minor landslides. The majority of these features lie in the area upstream of Shanker’s Bend. All of these sources were observed in both the 1953 and 2000 set of aerial photographs, and the sizes or extent of these features have not measurably changed. Most of the upland sources, however, do not appear to have a direct connection to the Similkameen River, as the sediment eroded from these sources is deposited upgradient of the highway roadbed (to the north) or the railroad bed (to the south).

The river channel conditions and morphology upstream and downstream of the impoundment remained largely unchanged suggesting that sediment production from upland sediment sources is relatively minor, and that periodic high flows strip away any accumulated fine sediment load (gravels, sands and silt) and deposit the load in the impoundment (as attested to by the small and large sand bars along the RB) or in the Okanogan River. Further, because the river is entrenched over the entire study area, there is little chance to alter the stream planform, except near the confluence of the Similkameen and Okanogan Rivers, where minor shifts in the channel planform are noted.

Just upstream of the confluence with Okanagon River, the Similkameen River meanders more; between 1953 and 2000 the river in this area has undergone minor bank erosion with several adjustments to the channel planform. The 2000 photos reveal more exposure of point bars and sidebars compared with the 1953 photos, but these

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 22 August 2008 Public Utility District No. 1 of Okanogan County Final License Application changes are most likely due to the reduced flow recorded on July 29, 2000 (1360 cfs) when compared with the flow on July 2, 1953 (6770 cfs).

The field reconnaissance assessment indicated that within the channel upstream of the impoundment, zones of fine-grained sedimentation are scattered and generally small in size and volume. Tributary sources are minimal and limted to a few gullies. Coarser material (cobbles and boulders) is abundant, and the channel morphology is influenced most by its level of incision into the glacial overburden and/or bedrock.

Within the reservoir, channel width is relatively uniform and the reservoir substrate is dominated by sands. The few sediment sources within the impoundment area (colluvium from road fill, a gully draining badlands along the LB, and the long erosional scars associated with the high water lines along the RB) are considered relatively small in overall sediment production, although perhaps can be farily productive during exceptional rain storms and/or high flows.

Downstream of the dam, zones of fine-grained sediment sources are rare, although the extensive landslip/badland cuts just downstream of the old railroad crossing could potentially produce high volumes of fine-grained material during exceptional rain storms and/or high flows. Further, there are in general few fine-grained sediment deposits suggesting that there are minimal fine-grained sediment sources. Tributary sources of sediment are essentially non-existent. Within the canyon, coarser material (cobbles and boulders) is abundant, and the channel is shaped primarily by bedrock. Downstream of the canyon, the river is confined by relatively high terraces (protected by rip-rap) and dikes, and the substrate is composed of predominantly cobbles and large gravels.

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 23 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

This page is left intentionally blank.

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 24 August 2008 Public Utility District No. 1 of Okanogan County Final License Application

Table 1: September 25 and 26, 2007 Raft Reconnaissance Station Descriptions

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description DOWNSTREAM OF DAM, September 25, 2007

Both banks contain rock talus P001 Adjacent to powerhouse; looking and boulders. Deep pools in upstream at old powerhouse on RB; main channel Enloe Dam at center right Boulders on bedrock P002 Looking downstream at RB

Old powerhouse, steep Channel substrate apparently P003 Looking upstream canyon walls with increased sand content A downstream from station A. Small sand bars formed in P004 Looking at RB large boulders and bedrock along RB Narrow partially vegetated P005 Looking at LB bench at base of valley walls comprised of steep bedrock cliffs or angular boulders strewn on colluvial slope Small talus slope containing P006 Looking at RB at sand and rock talus rock and sand from top of railroad bed. Bedrock and boulders in pool- P007 Looking upstream dominated channel B Small sand bar P008 Looking upstream at RB

Cascades in bedrock-boulder P009 Looking upstream dominated channel P010 Looking st LB and small dredging operation Sand bench (approx. 100 ft Colluvial talus present at base High water line on both sides P011 Looking upstream; steep bedrock C long). of outcrop. of bank composed of silt. cliffs and small sand bar along LB; high water line is white band of silt

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 25 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description P012 Large rock talus along RB

Loose thin talus; angular Pockets of small colluvial Adjacent to BLM landfill P013 Looking across and downstream cobbles, trace gravels, cobble- talus; fine-grained. along LB and gulley and a BLM boulder bar exposed near LB gabion near hill top P014 Looking across and downstream along LB and gulley and BLM gabion D near hill top Coalescing rock talus along Isolated sand or cobble bars P015 Looking upstream RB along LB Thin sand veneer along LB P016 Looking upstream ot location just upstream of E Thin grassy covered sloping RR grade present approx. 75 P017 Looking upstream at RB bench at base of rilled, gullied feet upland. E colluvial partially-vegetated talus On boulder-cobble bar with P018 Looking upstream from large mid- F small pockets of fine sand; channel cobble-boulder bar valley/canyon widens Unconsolidated alluvium Predominantly foliated P019 Looking at RB unconformably lies on schistose meta-sedimentary schistose meta-sedimentary with fine-grained colluvium rocks across side channel P020 Looking at LB at truncated alluvial fan from cobble-boulder bar

P021 Looking at LB from cobble-boulder bar Sediment bar present. A steep Slope and topography is P022 Looking at LB; raft crew in foreground gully drains to a truncated similar to left bank; topography alluvial fan (approx. 300 ft is of lower elevations. long) at channel; comprised of mostly angular, slatey material

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 26 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description Channel comprised of P023 Looking at LB boulders and cobbles on bedrock Meta-sedimantary schistose P024 Looking upstream bedrock Steep fine-grained soil and Abundant vegetation of mixed Valley narrows with steep no sediment with pockets of deciduous-conifer stands walls and pockets of fine photo colluvial talus. colluvial talus; stream channel G comprised of bouldery rapids Bedrock-boulder rapids P025 Looking upstream at rapids between G & H Pockets of sand and boulders Sand bars present (50 - 150 ft Stream channel widens below P026 Looking upstream at RB on steep slope in length); sandy gravelly fan rapids. mixed with cobble-boulder bar

High isolated sand bar on Below H, very narrow pool; P027 Looking upstream at LB H steep rocky slope bedrock steep on both RB and LB with some rock talus P028 Looking upstream at rapids between H & I Bedrock Deep pools in main channel P029 Looking upstream from above I

Sand and gravel bars behind Steep (vertical in places); Mid channel rock islands P030 Looking upstream from mid channel large rock island vegetated talus below railroad present. Large accumulation grade of gravels and sand behind I rock island; 150 x 300 ft. irregular shaped with pools and back eddy Large isolated bedrock island P031 Looking downstream from top of rock along side channel with large island sandy gravelly bar downstream of rock island Rock talus on RB slopes Deep pools with bedrock in P032 Looking upstream from top of large main channel rock island

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 27 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description P033 Looking upstream from large gravelly cobbly bar; person on bedrock knob and raft for scale Cobble-boulder bar Colluvial talus on RB P034 Looking across river

Steep bedrock walls exposed Narrow sand bar present. Stream channel cuts narrow P035 Looking upstream at RB to bank. Bedrock exposed on bank. canyon, exposed bedrock. P036 Looking downstream J

Vertical bedrock wall on LB Rock talus and near vertical P037 Looking upstream from downstream with house under construction bedrock walls of J Minor fine-grained colluvial Predominantly steep bedrock P038 Looking downstream talus. walls in this location; bedrock in channel pools High water lines much higher in narrow canyons. Seepage zones (dry at time of photo) on lower canyon walls. K P039 Looking upstream; small sand bar at base of steep bedrock wall on RB

P040 Looking downstream from downstream of K at railroad bridge crossing; steep canyon walls on both RB & LB Partially revegetated stable P041 Looking at RB (across from Taber's sand talus apron (slope) below cabin) L bedland, with retreating headscarp and bouldery armor at base

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 28 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description Gently sloping valley walls Steep valley walls with Valley opens up considerably, P042 Looking upstream at LB containing sandy to bouldery erosional headscarps 20 - 100 vegetation consists of mixed vegetated side bars with ft high cut into unconsolidated grasses and conifers. Bare willows and grasses and partially vegetated sandy slopes present; erosion interspersed bedrock. alluvium. Cobble-boulder evident. boulders and bedrock bench armors high water line; in main channel likely winnowed at high flows; some LWD on slope; bare slopes in upslope areas Bedrock in channel P043 Looking downstream at RB M Bedrock protecting stable high P044 Looking downstream at LB sandy bar with grass and conifers Grassy cobble-boulder bar P045 Looking downstream from just downstream of M at LB Steep bank is cut into P046 Looking upstream from just upstream unconsolidated sandy of N at RB alluvium; partially vegetated sandy cobble bar at base and downstream of cut. Sand and gravel bars with Rip-rap present 20 ft high to P047 Looking upstream grass and willows. protect farm land from erosion; extends approx. 300 ft along N bank. Gently sloping vegetated bars; steep banks and high terrace P048 Looking downstream at RB low terrace on LB on RB Bank consists of cobbles, Bank consists of cobbles, Historical bridge crossin west No boulders, little sand. Bank boulders, little sand. Bank of Oroville Photo O appears stable. Dike present. appears stable. Dike present. Rip-rap Vegetated sand and gravel bar Bars present consisting of Adjacent to Oroville. Old No boulders and cobbles. bridge crossing with cement photo P blocks and rebar; wooden piers

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 29 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description High grassy bench with Adjacent to Oroville. Stream No cobbles; bank is cut with redds channel widens at meander; Photo Q at base cobble boulder channel with silt blanket

UPSTREAM OF DAM, September 26, 2007

Gentle to moderate slope with Bedrock exposed at channel. Channel bottom consists of P049 Looking north at LB. boulders and grasses. No Steep angular boulders sands and gravels and exposed sediments. Medium present with rock talus. boulders. R density vegetated riparian zone. P050 Looking south at RB; railroad cut and talus Banks contain patches of Sandbar present. Gentle Badland slopes present P051 Looking south at RB exposed fine-grained soils. slopes present upland with upland of LB grasses. S Cobble-boulder bar; gentle P052 Looking downstrean at RB slopes; light density vegetation Partially vegetated steep slope P053 Looking north at RB with armored bank Very little sediment sources Stream bottom consists of P054 Looking upstream at badland hills, present at bank. Little boulders, cobbles and small road cut above LB T evidence of erosion. Gently patches of sands. Badlands sloping and armored. present upland of right bank. Sand present below rapids. Exposed 300 ft section of fine Medium sloped bench Glacial deposits and badlands P055 Looking at LB colluvium (rock talus at base). present upland U Historic Tonasket-Okanogan aquaduct in cut Partially vegetated talus with P056 Looking upstream at LB cobble-boulder armor at base Badland gulleys and railroad P057 Looking south at RB cut erosion scar behind relatively stable armored

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 30 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description banks

P058 Looking south at RB just downstream of previous photo Colluviated slopes with Culvert crosses railroad gulley P059 Looking south at RB cobble-boulder armor at base; boulder-cobble fan at mouth of small gulley Boulder field present along Steep slopes, rock talus with Stream narrows in this area. P060 Looking downstream at LB LB; bedrock outcrops; willows exposed colluvium on outside and grasses present on higher bend of meander. Shrubs and bench; colluvial sandy talus small trees present. P061 Looking downstream at RB

V P062 Looking upstream

P063 Looking south at RB

P064 Looking uupstream at RB

Very steep bank with rock Near vertical bedrock walls High water line observed 4 to P065 Looking downstream W talus. Sand, boulders, and 5 feet above surface water bedrock present. elevation Steeply sloping exposed Exposed fine-grained Wide flat-bottomed channel P066 Looking downstream bedrock with colluvium, colluvium and talus, partially cobbles, and gravel at base; vegetated very little bank material P067 Looking downstream X

P068 Looking downstream at RB

P069 Looking upstream

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 31 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description No bank present. Steep, near Colluvial slopes and bedrock On extensive boulder-cobble P070 Looking at LB vertical walls (>40 ft high). with scattered mixed forest bar with gravel pockets; vegetation. scattered willows; signigficant drop in thalweg in channel opposite bar. Small tributary enters river. Small boulder- cobble armored alluvial cone present with minor sediment contribution. P071 Looking downstream on boulder- cobble bar P072 Looking at LB Y P073 Looking at mouth of small tributary

P074 Looking downstream from alluvial fan onto boulder-cobble bar and RB P075 Looking downstream at gravel pockets within boulder-cobble bar Gravelly bar along base of Sand bar formed at P076 Looking at LB downstream of Y moderately sloping lightly downstream end of boulder- vegetated slope cobble bar P077 Looking at RB downstream of Y

Pockets of sands and cobbles Scattered angular talus. Bedrock present at base of P078 Looking upstream with grasses. stream channel with sand and Z gravel. P079 Looking downstream

Fill present from roadbed Sand bar present (150 ft x 50 P080 Looking upstream at Haystack Rock exposed with scattered ft wide). Exposed gravel AA vegetation. Banks are terrace present. moderately steep and contain grasses.

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 32 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description Deep pool in channel center P081 Looking across channel at LB, extensive badlands and road

Cobble-boulder bar and P082 Looking downstream armored bank Cobble-boulder channel P083 Looking upstream at Haystack Rock substrate P084 Looking downstream along RB

Near vertical oversteepened Stable bank. Boulder bars and 300 ft wide stream channel. P085 Looking at LB slopes with sloughing trees, bench with Ponerosa Pine Bottom of channel contains LWD boulders, gravels and sand.

AB P086 Looking downstream at LB

P087 Looking downstream at LB

P088 Looking downstream at LB

Glacial material and colluvial Boulder field present on P089 Looking upstream at RB and AC slopes present. Boulder armor banks. Banks are gently extensive badlands in distance along bank. sloping at stream channel; steeper at railroad bank. P090 Looking downstream

Boulders present at bank. Sandbar present over At Miner's Flat; channel P091 Looking at LB, gravel boat ramp from Partly vegetated colluvium bedrock. Upper slopes appear substrate is cobble-boulder Miner's Flat in center of photo upland. stable. AD P092 Looking downstream

P093 Looking at RB

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 33 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description Bedrock present. Appears Mussel beds are present at Railroad bed present approx. P094 Looking at RB stable. Steep banks with base of 'end-dumped' boulder 25 feet above stream channel. isolated sand bars piles; grassy sand bars Exposed unconsolidated till downstream of pile upland. Just upstream of FERC Boundary AE P095 Looking at LB

P096 Looking at RB

Bedrock present. Appears Gentler slopes. Bedrock Substrate changed to cobble P097 Looking at LB stable. Small colluvial apron exposed in places. Appears dominated originating from road; boulder- stable. AF armored banks P098 Looking at LB

Sandy bench present with Remnant boulders and Downstream into Shanker's P099 Looking at thin sand bar along RB bedrock exposed; extensive cobbles below sandy bench Canyon vertical rock walls are exposed cobble bar below containing grass. present on both sides of the bench stream channel. P100 Looking downstream along RB AG

P101 Looking downstream

P102 Looking downstream along RB

Road fill colluvium present for Bedrock present with Stream channel bottom P103 Looking upstream at RB approx. 500 feet. vegetated sandy bench and dominated by sands with AH small sand bars at base of gravel and scattered cobbles near-vertical cliffs P104 Looking downstream along LB

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 34 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Obs. Left (Northern) Bank Right (Southern) Bank Main Channel Observations Photos Photo Orientation Stn. Description Description P105 Looking downstream along RB

P106 Looking downstream along RB

Small gravel-cobble fan and P107 Looking at LB culvert below road Steep bedrock present Partially vegetated extensive P108 Looking at RB thick sandbar at base of steep bedrock canyon wall. Vegetation covered benches are likely submerged during AI periods of high flow. P109 Looking downstream along RB

P110 Looking upstream at RB from downstream of AI High water mark; steep banks, Extensive erosional scars P111 Looking upstream at upper bedrock in places along RB impoundment P112 Looking downstream at mid impoundment AJ P113 Looking downstream at mid impoundment Colluvial slopes with grass P114 Looking at LB and shrubs at base Bench cut into toe of alluvial Shallow water - bottom of P115 Looking at RB AK fan. Erosion evident at high impoundment easily visible; water mark. substrate - ripple morphology

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 35 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

This page is left intentionally blank.

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 36 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Table 2: September 27, 2007 Vehicle Reconnaissance Station and Photo Descriptions

Station Photo # Description Looking upstream of lower Similkameen River Valley at landslide along RB valley V001 1 wall V002 Looking downstream at lower Similkameen River Valley; Oroville on left distance V003 Looking southwest across river channel at landslide 2 V004 Looking southwest across river channel at rip-rap protecting RB below low terrace Panorama: landslide to Taber's - looking across river channel at 3 V005 to V007 erosional/landslide scars 4 V008 Looking across channel at landslide V009 Looking up valley at canyon - new house in distant center 5 V010 Looking downstream: lower Similkameen River joins Okanogan River Valley V011 Looking upcanyon; paleochannel on raised terrace on left 6 V012 Looking downstream at historic railroad bridge V013 Looking across channel at rock talus cones along RB Panorama of southern wall with erosional scars near river channel; from old V014 to V017 7 powerhouse (distant right) to below golf course V018 Plane Looking upstream at mid-section of impoundment; historic railroad tunnel in distant V019 center 8 V020 Looking down at forebay area

9 V021 to V025 Panorama of impoundment; tunnel to lower reservoir

10 V026 Looking upstream at badlands above Shanker's Bend and sand bar along RB V027 Looking downstream at sand bar below Shanker's Bend 11 V028 Looking upstream at small sand bar below steep cliff at Shanker's Bend Looking upstream at sand bars above Shanker's Bend and at upstream limit of 12 V029 impoundment 13 V030 Looking downstream towards Shanker's Bend and small gulley draining badlands Looking upstream at 'Haystack Rock' and sand and cobble bars downstream of V031 Haystack; note bedrock forming channel bottom and deep pools upstream of 14 bedrock Looking downstream; wide flat bottom channel with steep banks and cobble- V032 boulder bars 15 V033 Looking downstream just below haystack

16 V034 to V036 Panorama: looking downstream to upstream at sand bar to boulder bar

17 V037 At badland - RR bed at base (unable to see river below) Looking upstream - small erosional scar from RR line in distance and center, BLM 18 V038 camp on right; generally stable gently sloping banks

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 37 August 2008

Public Utility District No. 1 of Okanogan County Final License Application

Station Photo # Description V039 Looking upstream from BLM camp; railroad erosional scars to left 19 V040 Looking across channel at erosional scars associated with railroad cut V041 Looking downstream; erosional scars associated with railroad cut on right Looking upstream; note gentle to moderately sloping valley and relatively stable V042 20 riparian zone (little sediment sources) V043 Looking downstream Looking upstream; note historic irrigation diversion structure in distance on LB, V044 diversion channel and old Tonasket-Okanogan irrigation canal 21 V045 Looking downstream; river is fairly wide and shallow; gently sloping banks, with gravel-cobble bars

V046 Looking upstream from near USGS gage station at Similkameen River Valley at 22 Nighthawk; note gentle gradients and stable banks

Enloe Hydroelectric Project Exhibit E – Environmental Report FERC Project # 12569 Appendix E.6.2 Bank Stability and Erosion Assessment 38 August 2008

ATTACHMENT A: PHOTOLOG

Public Utility District No. 1 of Okanogan County Final License Application

Photo P001, Station A: Adjacent to powerhouse; looking upstream at old Photo P003, Station A: Looking upstream powerhouse on RB; Enloe Dam at center right

Photo P002, Station A: Looking downstream at RB Photo P004, Station A: Looking at RB