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Home , Chelan River, Coulee, Rocky Reach Dam, Wells Dam

DYNAMICS IN THE ROCKY REACH PROJECT AREA

Final

ROCKY REACH HYDROELECTRIC PROJECT FERC Project No. 2145

December 15, 2000

Prepared by: BioAnalysts, Inc. Boise, Idaho

Prepared for: Public Utility District No. 1 of Chelan County Wenatchee,

Sediment Dynamics

TABLE OF CONTENTS

SECTION 1: INTRODUCTION ...... 1

SECTION 2: PROCESSESS...... 2

SECTION 3: SEDIMENTATION PATTERNS...... 4 3.1 Deltas...... 4 3.2 Suspended Sediment Patterns...... 5 3.3 Deposited Sediment Patterns ...... 5

SECTION 4: DOWNSTREAM EFFECTS...... 16

SECTION 5: SUMMARY...... 17

SECTION 6: REFERENCES ...... 18

APPENDIX A: ADDITIONAL AERIAL PHOTOS OF THE LOWER ENTIAT

LIST OF FIGURES

Figure 3-1: Timeline of major events in the Entiat River drainage...... 6 Figure 3-2: Aerial photograph of the lower Entiat River in 1910...... 7 Figure 3-3: Aerial photograph of the lower Entiat River in 1930...... 8 Figure 3-4: Aerial photograph of the lower Entiat River in July 1946...... 9 Figure 3-5: Aerial photograph of the lower Entiat River in 1955...... 10 Figure 3-6: Aerial photograph of the lower Entiat River in September 1968...... 11 Figure 3-7: Aerial photograph of the lower Entiat River in August 1975...... 12 Figure 3-8: Aerial photograph of the lower Entiat River in July 1985...... 13 Figure 3-9: Aerial photograph of the lower Entiat River in July 1992...... 14 Figure 3-10: Aerial photograph of the lower Entiat River in October 1998...... 15

Figure A 1: Aerial photograph of the lower Entiat River in 1945...... 23 Figure A 2: Aerial photograph of the lower Entiat River in 1954...... 24 Figure A 3: Aerial photograph of the lower Entiat River in August 1989...... 25

Final Study Report Rocky Reach Project No. 2145 December 15, 2000 Page i SS/2487

Sediment Dynamics

SECTION 1: INTRODUCTION

Hydroelectric facilities alter sediment transport and within channels (Baxter and Glaude 1980; Williams and Wolman 1984; Spence et al. 1996; Brookes 1996; Nilsson and Berggren 2000). This alteration can significantly influence the ecological response of the system. Considering the physical accumulation of sediment in reservoirs alone indicates its potential importance in ecosystem structure and function. For example, upstream from most fine sediment settles to the bottom, covering coarser substrate and depriving downstream reaches of sediment input. The reduction in sediment downstream of dams leads to changes in morphology (Williams and Wolman 1984; Marcus et al. 1990; Nilsson and Berggren 2000). In addition, deposited upstream from dams may carry pesticides and herbicides, organic residues, nutrients, and pathogenic organisms, which can affect the biota within the river (Baxter and Glaude 1980; Sharpley et al. 1987; McCarthy and Gale 1999).

Rocky Reach is essentially a “run-of-the-river” project. Flows pass through as turbine and/or spill, creating noticeable river currents. Nevertheless, has presumably affected the sediment dynamics within the project area1 by reducing water velocities upstream from the project. This report reviews existing information on the effects of Rocky Reach Dam on the sediment dynamics within the project area. The report first briefly discusses sediment transport processes. It then describes sedimentation patterns and deposition zones. At that point in the report we examine aerial photos to describe sediment deposition near the mouth of the Entiat River, an important source of sediment to Rocky Reach Reservoir. Finally, the report discusses sediment processes downstream from Rocky Reach Dam. Because there is virtually no information on sediment dynamics within the project area, we extrapolate general information in the literature to the project area. This obviously assumes that general information on sediment dynamics applies to the Rocky Reach project area. We conducted no field studies to validate this assumption. The Rocky Reach Natural Sciences Working Group will use this report to formulate management decisions and plans.

1 The Rocky Reach project area extends from the upstream end of Rocky Reach Reservoir to Rock Island Reservoir.

Final Study Report Rocky Reach Project No. 2145 December 15, 2000 Page 1 SS/2487 Sediment Dynamics

SECTION 2: SEDIMENT TRANSPORT PROCESSESS

The amount of sediment transported to a reservoir is directly related to the size of the upstream from the reservoir (Baxter and Glaude 1980; Thornton et al. 1990). That is, larger drainage basins associated with reservoirs generally result in greater annual flows entering the reservoir and therefore potentially greater sediment and nutrient loads. Although the drainage area upstream from Rocky Reach Dam is huge (87,800 mi2 or 227,402 km2), sediment transport to the project area is low (CPUD 1991). This is because sediments from the upper basin are deposited in Roosevelt Lake upstream from .2 Wells Reservoir traps most sediments that originate from the Okanogan and Methow basins and the Columbia River between and . Lake Chelan traps sediments from the Chelan Basin. Therefore, inputs of sediments to the Rocky Reach project area come from sediments passing through the Wells project, a relatively small area just downstream from Wells Dam, the , the Entiat Basin, and several mostly ephemeral or intermittent that drain directly into the reservoir. The Columbia River and Entiat River basin (419 mi2 or 1,085 km2) are probably the largest contributors of sediment to the Rocky Reach Reservoir.

Other factors such as geology, soil types, topography, climate, fires, and land uses within the basin upstream from the reservoir also affect sediment transport (Baxter and Glaude 1980; Dingman 1994). The Rocky Reach project area lies between two different physiographic areas (CPUD 1991). To the west, the Cascade Mountains are comprised of highly metamorphosed schists and gneisses, slightly metamorphosed marine sedimentary rock, volcanic rocks, and granitic batholiths. To the east, the Columbia River Plateau consists mostly of basalt. The last glaciation deposited till on top of the basalt. These rock types are fairly resistant to .

Topography in the mid-Columbia Basin is steep and dissected. Soils in the area consist of two basic types (CPUD 1991). Near the toe of rock slopes, soils are mainly colluvial and composed of angular rock fragments. Here, soils are well graded, and soil fragments range in size from clay to large boulders. In the lowlands the predominant soils are fluvial and lacustrine. These soils range from clay to gravel and cobbles. Mullan et al. (1992) described the soils as highly erodible and unstable. The climate consists of hot, dry summers and mild to severe winters. Precipitation varies widely depending on the elevation and proximity to the Cascade Mountains. Mean annual precipitation varies from 35 inches (89 cm) in the lower Cascades, to about 11 inches (28 cm) on the Columbia Plateau, to 8.5 inches (22 cm) in the project area (CPUD 1991).

2 Grand Coulee Dam was built in 1942. Therefore, it affected flows and sediment dynamics in the project area long before Rocky Reach Dam was constructed. In , large storage facilities such as Hugh Keenleyside, Mica, and Revelstoke dams were built in 1968, 1973, and 1983, respectively. Sherwood et al. (1990) and Chapman et al. (1994) concluded that storage in the upper Columbia River has altered the of the main Columbia River. Sherwood et al. (1990) analyzed monthly mean flows of the Columbia River, and found that large-scale regulation of the flow cycle began around 1969. They noted that river storage and flow regulation has greatly reduced the probability of large freshets having important sedimentological effects in the Columbia River.

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Land uses vary in the project area. Residential developments, orchards, irrigated pastures, and roads occur along the reservoir (CPUD 1991). In the Entiat Basin, land uses include roads, mining, grazing, logging, irrigation, orchards, and residential developments (Mullan et al. 1992). Most intense land uses occur in the lower basin (Mullan et al. 1992). Wildfires have been a problem and their effects on sediment recruitment to streams has probably increased because of land uses within the basin. All these factors tend to increase sediment transport to streams. Mullan et al. (1992) indicate that sediment delivery to the Entiat River is about 10% above natural background levels. Even so, waters in the project area have relatively low turbidity (CPUD 1991). Although turbidity ranges from 2 ft (0.6 m) to 18 ft (5.5 m) (secchi disk visibility) in the project areas, secchi disk readings are generally greater than 12 ft (3.7 m) visibility (CPUD 1991). This is probably because of the geology and geomorphology (i.e., glacial-carved valleys) in the project area. As a result, Rocky Reach Reservoir has trapped relatively low volumes of sediment (CPUD 1991).

As a final note, sediment, particulate organic matter, and adsorbed constituents are transported primarily during storm events or elevated flows (Bilby and Likens 1979; Baxter and Glaude 1980; Kennedy et al. 1981). There also appears to be a strong seasonal component to suspended sediment transport. This seasonality is generally a function of both watershed land-use and stream production (Thornton et al. 1990). Probably the majority of suspended sediment input comes from the Columbia River upstream of Rocky Reach Reservoir and from the Entiat River.

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SECTION 3: SEDIMENTATION PATTERNS

3.1 Deltas As streams and drain into reservoirs, their water velocities and turbulence begin to decrease resulting in reduced sediment-carrying capacity. The deposition of sediments near the mouths of these streams and rivers result in the formation of deltas (Ritter 1986). When streams and rivers enter the reservoir, the flow velocity, sediment load, and particle-size distribution vary both laterally and longitudinally. The longitudinal dimension is probably most important in reservoir delta formation. The large particles transported as bedload3 are the first to be deposited. As water velocities and turbulence further decrease smaller particles are deposited. This results in a longitudinal sorting of particles near the mouth of the stream or river. In reservoirs, the dynamic process of delta formation, migration, and reformation will change following major hydrometeorological events.

We used aerial photographs to examine the formation of the Entiat River delta after the closure of Rocky Reach Dam. We compiled ten aerial photographs dating from 1910 to 1998 and constructed a timeline of events (Figure 3-1) that probably influenced the quantity and rate of sedimentation. In 1910 the town of Entiat was established and fruit orchards covered the river (Figure 3-2). Near the center of the photograph in Figure 3-2 is the at a dam on the Entiat River, which was located about one mile upstream from the river mouth. The dam stored sediments until 1915 when it and most of the town of Entiat burned. The banks of the Entiat were vegetated and a gravel existed just downstream from the confluence (Figure 3-2). The photos taken in 1930 and 1946 show a large depositional zone in the Columbia River just downstream from the mouth of the Entiat River (Figure 3-3 and Figure 3-4). The photo taken in 1955 shows a straightened channel near the mouth of the Entiat (Figure 3-5), probably a result of channelization work by the Army Corp of Engineers in the 1940’s or early 1950’s. The present Highway 97 bridge was constructed in 1955 and 1956 (J. Klein, WDOT, personal communication).

Construction of Rocky Reach Dam changed the hydrology of the lower Entiat River. Although the photograph taken in 1968 is of poor quality, we see no evidence of large accumulations of sediment in the lower Entiat River at that time (Figure 3-6). The 1975 photo clearly indicates sediment deposition upstream from Highway 97 (Figure 3-7). Fires in the early 1970’s followed by heavy rains probably increased the rate of erosion and subsequent sediment deposition in the lower Entiat River. There is no evidence of a delta forming downstream from Highway 97 at that time. Ten years later, however, a delta had formed downstream from the highway along with several islands just upstream from the highway (Figure 3-8). The photo taken in 1992 indicates that the delta expanded and developed into what appears to be a spit along the right (south) margin (Figure 3-9). The islands upstream from the highway appear larger and vegetated. Finally, by 1998, deposition on the delta had formed a distinct spit along the right margin (Figure 3-10). It also appears that the left margin of the delta expanded. Islands upstream from the highway are heavily vegetated.

3 Bedload refers to sediment transported close to or at the channel bottom by rolling, sliding, or bouncing.

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These photos suggest that the Entiat River transports large quantities of sediment. Before the construction of Rocky Reach Dam, sediments were deposited on the Columbia River and in the Columbia River just downstream from the confluence of the Entiat River. After construction of the dam, sediments were deposited in the lower Entiat River and then into what is now the delta. Bugert et al. (1998) reviewed erosion studies and concluded that streambank erosion was not a significant problem on the Entiat River. Therefore, the combination of steep topography, frequent wild fires, heavy precipitation, and highly erodible soils contribute to the sediment load in the Entiat River. This load is responsible for the formation of islands and the delta in the Entiat River.

3.2 Suspended Sediment Patterns As we noted earlier, suspended sediment and other particulate matter are transported primarily during storm events and elevated flows. However, we found no studies that describe the movement of storm flow and its associated load through the Rocky Reach Reservoir. Studies in other areas suggest that storm flow and move along the old and pass through the reservoir in a few days (Kennedy et al. 1981). Because Rocky Reach is essentially a run-of-the-river project, storm flow and suspended sediments would move through the project quickly. At mean flows of 84,800 (July) and 131,000 cfs (May), water velocities in the Rocky Reach Reservoir average 1.02 and 1.59 ft/s, respectively (CPUD 1991). Reservoir turnover rates average 2.6 and 1.7 days, respectively (Bennett 1991). These velocities and turnover rates allow some suspended sediments to drop from suspension. Sedimentation would occur primarily in the upper portion of the reservoir and near the mouths of streams (e.g., Entiat River delta). During underwater surveys conducted in 1990 and 1991, Giorgi (personal communication) observed a layer of fine sediment (primarily silt) that covered certain areas several kilometers downstream from the Wells Dam tailrace. At this time, it is unknown what fraction of the suspended sediment load drops in the reservoir.

3.3 Deposited Sediment Patterns River and stream inflow and their constituent sediment loads generally follow the old river channel; therefore, sediment deposition initially is greatest in the old channel (Thornton et al. 1990). Typically, sedimentation rates are highest near the input source (river or stream) where sediment concentrations are highest, and decrease exponentially down the reservoir (McHenry et al. 1982). These deposited sediments are sorted longitudinally by particle size (Richards 1982). The largest particles are deposited first, primarily in or at the head of the delta areas in the reservoir. Then the larger, heavier sands and coarse silts settle in the deltas. As flow velocities and turbulence continue to diminish, additional particle-size sorting occurs along the longitudinal axis of the reservoir. The silts and coarse clays settle next with fine clays and colloidal material settling very slowly. In the Rocky Reach project area, water velocities in the reservoir would likely transport finer materials downstream.

The operation of dams often affect water level fluctuations. These fluctuations may influence sedimentation patterns by altering reservoir morphometry (length, depth, volume, etc.), mixing regime, water exchange between backwaters and the main pool, water residence time, and other factors (Thornton et al. 1990). However, because Rocky Reach is a run-of-the-river project and its operations allow for only a four-foot drawdown (CPUD 1991), it probably does not significantly alter sedimentation patterns through redistribution, resuspension, and erosion of deposited sediments.

Final Study Report Rocky Reach Project No. 2145 December 15, 2000 Page 5 SS/2487 Sediment Dynamics

Altered sediment patterns are usually associated with larger storage projects where storage during elevated-flow periods results in delta formation and sedimentation. During low-flow periods the deposited sediments become resuspended and transported further into the pool. We found no evidence that this occurs in the project area. If it does, it would most likely happen in the lower reaches of major streams (e.g., Entiat and Chelan rivers) and at the head of the reservoir.

Construction of Great Northern Railway

Mad River Gorge Gray mill in Johnson Mad River Fire to Blue Creek Dam and sawmill constructed Signal Peak/ Creek burned. Spectable Butte Fire Meadows Fire 1 mile above river mouth Tyee Fire Borealis Ridge Fire

1880 1890 1900 1910 1920 1930 1940

Gray sawmill and First establishment most of town of Last remnant Coal oil Fire in Entiat Valley Entiat below of the first town Numeral Mountain of Entiat burned burned

Entiat Slide Ridge Fire Gold Ridge Fire Mills Fire

Hornet Creek Fire

Larch Lake Fire Rocky Reach Dam High intensity rainstorm [Jan.] Dick Mesa Fire Reconstruction of Highway 97 Bridge

1940 1950 1960 1970 1980 1990 2000

Forest Mountain Fire High intensity rainstorm [June] Tyee Fire June washed Entiat Fire out bridges and Tena George Fire Harris Mill Fire Crum Canyon Fire Dinkelman Fire destroyed road in places

Figure 3-1: Timeline of major events in the Entiat River drainage.

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SECTION 4: DOWNSTREAM EFFECTS

Because reservoirs act to some degree as sediment traps, water released from a project has energy to entrain and transport sediments downstream from the dam. That is, degradation or scour occurs in the streambed downstream from the dam as the river entrains a new sediment load to replace what was deposited in the reservoir. For example, Williams and Wolman (1984) documented changes that occurred within alluvial channels downstream from 21 dams, mostly in the semiarid western U.S., over a period of up to 70 years. Dams reduced flood peaks 3-91%, with an average of 39% of the pre-dam values. Erosion of the channel bed occurred at all sites, with a maximum scour of 7 m occurring immediately downstream from the dam and decreasing further downstream. The response of channel width to dam closure was more variable. Widths decreased, increased, or remained constant depending on site characteristics.

The extent of erosion downstream from a dam depends in part on the sediment trap efficiency4 of the reservoir (Brune 1953). Trap efficiency is higher in reservoirs on bedload streams than on suspended load streams, is reduced by sluice operation in reservoirs, and increases with the water capacity:inflow ratio. Because Rocky Reach is a run-of-the-river project, sediment trap efficiency should be relatively low; however, as far as we know, no one has estimated the trap efficiency of Rocky Reach Reservoir.

Brookes (1996) noted that downstream channel changes from clear-water erosion also depend on the relative sizes of the discharge and on the initial sedimentology of the river. In general, regulated streams with heavy sandy bedload undergo more extreme morphological adjustments than sand- gravel-cobble streams. If bed material is a sand-gravel mixture and discharge peaks are not too depressed, bed degradation continues until the stream flows become incompetent to move the layer (Richards 1982). As the finer material is eroded, the bed becomes paved with heavier non- movable materials resulting in less bed erosion. This appears to be the case at Rocky Reach. Typically, as bed erosion stops, erosion occurs. Bank erosion at Rocky Reach is probably minimal because boulder rip-rap armors most banks.

4 Trap efficiency is measured as the percentage of incoming sediment that is stored in the reservoir. The higher the trap efficiency, the lower the percentage of sediment passing through the reservoir.

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SECTION 5: SUMMARY

After its construction, Rocky Reach Dam changed the sediment dynamics within the project area. Before construction, sediments were readily transported through the present-day project area. Sediment deposition did occur in low-gradient areas, such as in the Columbia River just downstream from the mouth of the Entiat River. After construction of Rocky Reach Dam, sediment deposition occurred in areas near the source of the sediment input (e.g., lower Entiat and Chelan rivers, and at the head of Rocky Reach Reservoir). In the Entiat River, sediment deposition occurred first upstream from Highway 97. About 15 years after construction of Rocky Reach Dam, the Entiat River had deposited large amounts of sediment upstream from the highway. Sometime between 15 and 25 years after construction of Rocky Reach Dam a delta formed at the mouth of the Entiat River. The delta has since enlarged and formed a spit. Islands also formed upstream from the highway. These islands are now vegetated.

Input of sediments into the project area is a function of basin area, geology, soil types, topography, climate, fires, and land uses. Upstream reservoirs greatly reduce sediment loads into the project area. However, steep topography, frequent fires, land uses, erodible soils, and at times heavy precipitation locally (e.g., Entiat Basin) increase the transport of sediments into the project area. The coarse, dense sediments are deposited near the headwaters of the reservoir, while finer sediments (silts) are deposited along the longitudinal axis of the reservoir. Some silts and probably most fine clays and colloidal materials pass through the project area. The operations of Rocky Reach Dam likely do not significantly alter sedimentation patterns (i.e., redistribute, resuspend, and erode deposited sediments) in the reservoir. Downstream from the dam the river has likely scoured fine sediments from the riverbed resulting in a pavement of heavier non-erodible materials. Boulder rip-rap along most banks in the tailrace minimizes bank erosion there.

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SECTION 6: REFERENCES

Baxter, R. and P. Glaude. 1980. Environmental effects of dams and impoundments in Canada: experience and prospects. Canadian Bulletin of Fisheries and Aquatic Sciences 205:34 p.

Bennett, D. 1991. Potential for predator increase associated with a three foot pool rise in Rocky Reach Reservoir, Columbia River, Washington. University of Idaho. Report to Chelan County Public Utility District, Wenatchee, WA.

Bilby, R. and G. Likens. 1979. Effect of hydrologic fluctuations on the transport of fine particulate organic carbon in a small stream. and Oceanography 24:69-75.

Brookes, A. 1996. River channel change. Pages 221-242 in: G. Petts and P. Calow, editors. River flows and channel form. Blackwell Science, Cambridge, MA.

Brune, G. 1953. Trap efficiency of reservoirs. Transactions of the American Geophysical Union 34:407-418.

Bugert, R., D. Bambrick, L. LaVoy, S. Noble, B. Cates, K. MacDonald, S. Carlson, S. Hays, J. Lukas, P. Archibald, K. March, K. Bauersfield, and S. Bickford. 1998. Aquatic species and assessment: Wenatchee, Entiat, Methow, and Okanogan watersheds-FINAL. Chelan County Public Utility District, Wenatchee, WA.

Chapman, D. and eight others. 1994. Status of summer/fall chinook salmon in the mid-Columbia region. Don Chapman Consultants, Inc. Report to Chelan, Douglas, and Grant County Public Utility Districts, Wenatchee, WA.

Chelan County Public Utility District (CPUD). 1991. Application for raising the pool elevation from 707’ to 710’. Rocky Reach Hydroelectric Project No. 2145, Wenatchee, WA.

Dingman, S. 1994. Physical hydrology. Prentice Hall, Upper Saddle River, NJ.

Giorgi, A. 1991. Fall chinook salmon spawning in Rocky Reach Pool: effects of a three foot increase in pool elevation. Report to Chelan County Public Utility District, Wenatchee, WA.

Griffith, Phyllis. Nuggets from Entiat Valley Explorer #6-35. Entiat, Washington;2000 August 31;A:5(1).

Kennedy, R., K. Thornton, and J. Carroll. 1981. Suspended sediment gradients in Lake Red Rock. Pages 1318-1328 in: J. Stefan, editor. Proceedings of the symposium on impoundments. American Society of Civil Engineers, New York, NY.

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Marcus, M, M. Young, L. Noel, and B. Mullan. 1990. Salmonid-habitat relationships in the western : a review and indexed bibliography. USDA, Forest Service, General Technical Report RM-GTR-188, Fort Collins, CO.

McCarthy, K. and R. Gale. 1999. Investigation of the distribution of organochlorine and polycyclic aromatic hydrocarbon compounds in the lower Columbia River using semipermeable membrane devices. USGS Water-Resources Investigations Report 99-4051, Portland, OR.

McHenry, J., C. Cooper, and J. Ritchie. 1982. Sedimentation in Wolf Lake, lower Yazoo River basin, Mississippi. Freshwater Ecology 1:547-558.

Mullan, J., K. Williams, G. Rhodus, T. Hillman, and J. McIntyre. 1992. Production and habitat of salmonids in Mid-Columbia River streams. U.S. Fish and Wildlife Service, Monograph I, Leavenworth, WA.

Nilsson, C. and K. Berggren. 2000. Alterations of riparian ecosystems caused by river regulation. BioScience 50:783-792.

Richards, K. 1982. Rivers, form and process in alluvial channels. Methuen and Co., New York, NY.

Ritter, D. 1986. Process geomorphology. Second edition. Wm. C. Brown Publishers, Dubuque, IA.

Sharpley, A., S. Smith, R. Menzel, W. Berg, and O. Jones. 1987. Precipitation and water quality in the Southern Plains. Proceedings in Lake and Reservoir Management 3:379-384.

Sherwood, C., D. Jay, R. Harvey, P. Hamilton, and C. Simenstad. 1990. Historical changes in the Columbia River . Prog. Oceanog. 25:299-352.

Spence, B., G. Lomnicky, R. Hughes, and R. Movitzki. 1996. An ecosystem approach to salmonid conservation. TR-4501-96-6057, ManTech Environmental Research Services Corp., Corvallis, OR.

Thornton, K., B. Kimmel, and F. Payne. 1990. Reservoir limnology: ecological perspectives. John Wiley and Sons, New York, NY.

Williams, G. and M. Wolman. 1984. Downstream effects of dams on alluvail rivers. USGS Professional Paper 1286, Washington, D.C.

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APPENDIX A: ADDITIONAL AERIAL PHOTOS OF THE LOWER ENTIAT RIVER