Attachment 3 - GAIP.pdf

Gravel/Cobble Augmentation Implementation Plan (GAIP) for the

Englebright Dam Reach of the Lower Yuba River, CA

(photo of proposed gravel augmentation location)

Prepared for: Prepared by:

U.S. Army Corps of Engineers Dr. Gregory B. Pasternack

Sacramento District 39601 Lupine Court

1325 J Street Davis, CA 95616

Sacramento, CA 95814-2922

Contact: Mitch Stewart

(916) 557-6734

September 30, 2010

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Englebright Dam GAIP G. B. Pasternack, 2010

TABLE OF CONTENTS

1. LOWER YUBA RIVER BACKGROUND

1.1. Geomorphic History

1.2. LYR Salmonids History

1.2.1. Historical Population Accounts

1.2.2. Physical Habitat Conditions

1.3. LYR Geomorphology-Salmonids Nexus

2. GRAVEL/COBBLE AUGMENTATION

2.1. Gravel/Cobble Augmentation Defined

2.2. LYR Pilot Gravel/Cobble Augmentation

2.3. Methods for Gravel/Cobble Augmentation

2.3.1. Road Construction and Gravel Placement

2.3.2. Helicopter Delivery

2.3.3. Truck-Mounted Conveyor Belt

2.3.4. Dumping Gravel/Cobble off Roadside

2.3.5. Cableway Delivery

2.3.6. Gravel/Cobble Sluicing

3. PRE-PROJECT CHARACTERIZATION OF THE EDR

3.1. EDR Literature Summary

3.2. EDR Existing Data and Analyses

3.3. EDR Gravel/Cobble Deficit

3.4. EDR SRH 2D Model

3.4.1. EDR 2D Model Setup

3.4.2. Microhabitat Prediction Method

3.4.3. Sediment Transport Regime Prediction Method

3.4.4. EDR 2D Model Results

4. RECOMMENDED METHOD FOR GRAVEL/COBBLE AUGMENTATION

4.1. Elimination of Inadequate Methods

4.2. Best Method for The EDR

4.3. Detailed Concept for Sluicing Gravel Mix Down to EDR

4.4. Gravel/Cobble Placement Location

4.5. Gravel Cobble Mixture Design

5. 2010 EDR SPAWNING RIFFLE DESIGN DEVELOPMENT

5.1. Project Constraints

5.2. Project Goals

5.3. Design Objectives And Hypotheses

5.4. Design Concept

5.5. 2D Model Testing of Design Hypotheses

6. LONG-TERM GRAVEL AUGMENTATION PLAN

7. REFERENCES

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TABLE OF FIGURES

Figure 1.1. Location map of the Englebright Dam Reach (black box) in the Yuba catchment Figure 1.2. 1905 photo of the LYR near Parks Bar taken by G.K. Bilbert

(http://libraryphoto.cr.usgs.gov/photo_all.htm) Figure 1.3. Dredger forming high tailings berm out of a mining-waste point bar at

Rose Bar on 10/21/1937. (Photo from the California Transportation State Archive)

Figure 1.4. Photo of a gold mining operation on Sinoro Bar circa 1960. (Photo courtest of Ralph Mullican)

Figure 1.5. Adult Chinook salmon abundance for the LYR based on carcass surveys and coded-wire tagging

Figure 1.6. Photo of SRCS holding in bedrock/boulder section of the LYR near the mouth of Deer Creek (photo courtesy of Ralph Mullican)

Figure 2.1. Photo of the EDR below Narrows 1 showing the dominance of shot rock on the banks. The wetted channel is devoid of river-rounded gravel and cobble in this area

Figure 2.2. 500 short tons of gravel/cobble prior to injection into the Narrows II pool

Figure 2.3. Gravel injection on November 29, 2007. Gravel pile is located in zone of aeration downstream of the Narrows II powerhouse

Figure 2.4. Photo of stockpiled gravel/cobble left on the parking area and hillside after the 2007 pilot injection

Figure 2.5. EDR Hydrograph of 2008-2009 water years showing flow peaks and the timing of key activities

Figure 3.1. EDR topographic map showing locations of existing shot rock deposits.

Inset map shows location of study site within the Yuba River basin and within California

Figure 3.2. EDR water depth for increasing discharge from left to right (855, 4500, 10000, 15400 cfs). Color scale is different for each image

Figure 3.3. EDR water depth for increasing discharge from left to right (30000, 50500, 96100 cfs). Color scale is different for each image

Figure 3.4. EDR water velocity for increasing discharge from left to right (855, 4500, 10000, 15400 cfs). Color scale is different for each image

Figure 3.5. EDR water velocity for increasing discharge from left to right (30000, 50500, 96100 cfs). Color scale is different for each image

Figure 3.6. EDR Chinook spawning hydraulic habitat quality (GHSI) for 855 (left) and 4500 cfs (right). Color scale is identical for both images

Figure 3.7. EDR Shields stress for increasing discharge from left to right (855, 4500, 10000, 15400 cfs). Color scale is identical for each image

Figure 3.8. EDR Shields stress for increasing discharge from left to right (30000, 50500, 96100 cfs). Color scale is identical for each image

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Figure 4.1. Photo of the New Year’s 2006 flood drowning the area where a road would have to be built to use trucks and front loaders as the delivery method for gravel/cobble augmentation. Aggressive velocities were evident all along the north bank

Figure 4.2. Schematic of the gravel/cobble delivery system using a sluice method. 56 Figure 4.3. Landing area at the water’s edge of Englebright reservoir (left) and gravel road leading up to the hillcrest (right) Figure 4.4. Hillslope from road down to low terrace (left) and view from low terrace down to the Area A gravel placement location (right)

Figure 5.1. General schematic illustrating what is involved in the SHIRA framework.

Figure 5.2. Example of large wood stored in the EDR Figure 5.3. Design concept for using gravel augmentation in the EDR to possibly obtain a salmon-spawning riffle with diverse microhabitat features Figure 5.4. GHSI prediction for Area A at 855 cfs. Areas of green and blue are predicted to be preferred Chinook spawning habitat Figure 5.5. Shields stress prediction for Area A at 855 cfs Figure 5.6. 2D model predictions of Shields stress for flows of 10,000 cfs (left) and

15,400 cfs (right), focusing on the location of gravel placement below the Narrows I powerhouse (PH1). In both scenarios, Shields stress > 0.06 over the majority of Area A

TABLE OF TABLES

Table 3.1. Estimated gravel/cobble deficit for the EDR to have a diverse assemblage of morphological units (excludes any independent action related to rehabilitating Sinoro Bar). Assumes α = 0.5

Table 3.2. Maximum estimated gravel/cobble fill associated with α = 0.8 Table 3.3. SRH 2D model inputs and parameters for the discharges simulated Table 4.1. EDR gravel and cobble specifications (from USACE, 2007) Table 5.1. Design objectives and hypothesis for EDR gravel/cobble augmentation. 64

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OVERVIEW

The purpose of this report is to thoroughly document a plan for implementing a gravel/cobble augmentation program below Englebright Dam and to address its biogeomorphic impact on the lower Yuba River. As described below, Englebright Dam plays a crucial role in protecting the downstream region from being overwhelmed by sedimentary mining waste debris still being eroded off hillsides and stored in long sections of the channel network upstream. Most of the active lower Yuba River also still has tens of millions of cubic yards of sedimentary mining waste debris in it that pre-date

Englebright Dam and are still being re-worked as part of a highly dynamic, meandering gravel-bed river. However, the reach between Englebright Dam and the confluence with

Deer Creek is now almost devoid of river-rounded gravel and cobble necessary for salmon spawning. In particular, spring-run Chinook salmon that historically went far upstream would substantially benefit from a gravel/cobble augmentation program below

Englebright Dam. Yet the critical reach is in a narrow canyon that is difficult to access and manage, let alone place thousands of tons of coarse sediment into. Numerous issues have to be considered and addressed. That effort is facilitated by the existence of many studies of the river in recent years that form the basis for understanding the status and challenges ahead for the river.

This report covers topics related to preliminary planning efforts, pre-project characterization of the reach in question, design development for the specific 2010 next-phase pilot project, and long-term planning. Section 1 is an overview of the literature that describes what is already known about the river leading to a geomorphic and biological nexus for the action necessary to rehabilitate the river with respect to the impact of Englebright Dam. Section 2 explains what gravel/cobble augmentation is and how it may be implemented. Specific constraints and opportunities associated with the possible use of each method below Englebright Dam are described, including how specific methods affect site selection and project goals. Section 3 presents the pre-project characterization of the Englebright Dam Reach. That includes a summary of available data and information, a new estimation of the gravel/cobble deficit for the reach, 2D hydrodynamic modeling and analysis of results, and a conception of how the reach works

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in its baseline condition. Section 4 presents the details of the concept for how to get gravel to the river bed in the remote canyon. The recommended method involves sluicing gravel and cobble to the river. Section 5 explains and tests design concepts, objectives, and methods for the opportunity to place gravel in 2010 to yield immediate, preferred salmon spawning physical habitat. Section 6 describes a long-term plan for monitoring the outcome of the 2010 pilot project and then what actions should be taken thereafter to continue to rehabilitate gravel/cobble storage and enhance salmonid spawning habitat in the reach with additional augmentations over time.

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1. LOWER YUBA RIVER BACKGROUND

The 3,490-km2 Yuba River basin has hot, dry summers and cool, wet winters.

Relative to other Sierra basins, the Yuba has among the highest mean annual precipitation

(>1,500 mm), so it has been used for hydropower, water supply, flood regulation, gold mining and sediment control (James 2005). During the Gold Rush (mid- to late 1800’s), hillsides were hydraulically mined until several court decisions first outlawed the practice, then reinstated it with restrictions and taxes instituted to construct and pay for dams such as Daguerre Point Dam and Englebright Dam. These dams were designed to prevent the transport of hydraulic mining debris to the valley, thus lowering the risk of flooding. However, hydraulic mining never returned to the levels of the 1800's (Gilbert, 1917). Englebright Dam is located at 39°14'23.37"N, 121°16'8.75"W (Yuba River mile

23.9 upstream from confluence with the Feather River) in a narrow bedrock canyon on the Yuba River in northern California. Streamflow is recorded at the United States

Geological Survey Smartville gage (#11418000) 0.5 km downstream of Englebright

Dam. The gage’s statistical bankful discharge 1971-2004 was 5620 cfs (159.2 m3 s-1), which matches field indicators (tops of active medial bars and positioning of bank vegetation) for the bankful discharge in Timbuctoo Bend. Given that the Middle and

South Yuba tributaries lack large reservoirs, winter storms and spring snowmelt produce floods that overtop Englebright Dam. The Lower Yuba River (LYR) is ~38 km (24 mi) long from Englebright to the junction with the Feather. The Englebright Dam Reach

(EDR) extends from Englebright down to the confluence with Deer Creek (Fig. 1.1).

1.1. LYR Geomorphic History

No records are known to exist describing river conditions in the canyon that

Englebright sits in prior to placer gold mining in the mid-Nineteenth century. During the era of placer gold mining, Malay Camp on the northern bank of the Yuba close to the confluence of Deer Creek served as a base of operations for miners working Landers Bar, an alluvial deposit in the canyon nearby. The historical records of the existence of this camp and placer-mining site proves that coarse sediment was stored in the canyon prior

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to hydraulic mining in a large enough quantity to produce emergent alluvial bars.

During the period of hydraulic gold mining, vast quantities of sand, gravel, and cobble entered the Yuba River (Gilbert, 1917) and deposited throughout the system (Fig.

1.2). This human impact completely transformed the river. Historical photos from 1909 and 1937 document that the canyon was filled with alluvial sediment with an assemblage of river features including riffles (Pasternack et al., 2010). Conditions downstream of the canyon during that period were described by James et al., (2009). Even though Daguerre

Point Dam was built on the valley floor in 1906 (at Yuba River mile 11.4 upstream from confluence with the Feather River) to prevent the transport of hydraulic mining debris, it is too small to block sediment migration during floods.

Englebright Dam (capacity of just 82.6 million m3) was constructed in 1941 to serve as an additional, highly effective barrier to the hydraulic-mining waste material continuing to move down to the Central Valley. Thereafter, photos show that the amount of alluvium in the entire lower Yuba River, including the canyon, decreased (Pasternack et al., 2010). At the Marysville gaging station, the river incised ~20’ from 1905-1979, while 0.5 mi downstream of the Highway 20 bridge it incised ~35’ over the same period

(Beak Consultants, Inc., 1989). These landform adjustments are still on-going. For example, Pasternack (2008) estimated that ~605,000 yds3 of sediment (primarily gravel and cobble) were exported out of Timbuctoo Bend from 1999 to 2006. Further investigations of landform and sediment-storage changes are on-going, and the early indications are that they will show significant dynamism well beyond what was presumed by Beak Consultants, Inc (1989).

The reported changes conform with the expected, natural response of a river to blockage of downstream sediment passage (e.g. Williams and Wolman, 1984). For most rivers, such geomorphic changes represent a harmful human impact on a river, but in this case of pre-existing, unnatural snuffing of the river corridor by mining debris, the dam is actually restoring the river toward its historical geomorphic condition, in the truest meaning of the term- to go back to the pre-existing state prior to hydraulic gold mining.

Hydraulic mining is the primary disturbance to the Yuba River. Going back in this case means evacuating much of the waste debris associated with that historic practice.

Abatement of the downstream effects of sediment derived from uplands through the use

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of dams is an accepted practice for watershed rehabilitation (Shields, in press). On the

LYR, there is strong evidence that Englebright Dam has helped to evacuate sediment without hurting important channel processes. For example, despite the evidence that

Timbuctoo Bend is undergoing significant sediment export and river-corridor incision, White et al. (2010) reported that eight riffles persisted in the same locations over the last

26 years (likely back much further). Most of these persistent riffles are positioned in the locally wide areas in the valley, while intervening pools are located at valley constrictions. Thus, incision and sediment export do not necessary translate into harmful degradation of fluvial landforms. In Timbuctoo Bend, the existence of undular valley walls preserves riffle-pool morphology in the face of on-going geomorphic change.

Given the vast quantity of waste material still present in the upper system and the ability of many unhealed hillsides to generate more, Englebright Dam continues to serve as an important protection for the environment of the LYR.

Confounding the natural response of the river to the restorative impact of

Englebright, the Yuba River has been subjected to harmful in-channel human activities that further altered it. The greatest impact came from dredgers processing and re-processing most of the alluvium in the river valley in the search for residual gold and to control the river (James et al., 2009). First, there was the formation of the ~10,000 acre

Yuba Goldfields in the ancestral migration belt. Then there was the relocation of the river to the valley’s northern edge and its isolation from the Goldfields by large “training berms” of piled-up dredger spoils. Dredger-spoil training berms also exist further upstream in Timbuctoo Bend away from the Goldfields (Fig. 1.3); these berms provide no flood-control benefit.

Although no training berms exist in the canyon downstream of Englebright Dam, mechanized gold mining facilitated by a bulldozer beginning ~1960 (Fig. 1.4) completely reworked the alluvial deposits in the vicinity of the confluence with Deer Creek, changing the river’s form there (Pasternack et al., 2010). Prior to mechanized mining, glide-riffle transitions were gradual, enabling fish to select among a diverse range of local hydraulic conditions. Bulldozer debris constricted the channel significantly, induced abrupt hydraulic transitioning, and caused the main riffle at the apex of the bar to degrade into a chute. In addition, mining operations evacuated the majority of alluvium at the

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mouth of Deer Creek. On top of these impacts, the 1997 flood caused angular hillside rocks and “shot rock” debris from the canyon bottom to be deposited on top of the hydraulic-mining alluvium in the canyon.

At present, the Yuba River downstream of Englebright Dam continues to change in response to the complex assemblage of natural processes and human impacts. The legacy of hydraulic mining is the first and foremost impact to the system, relative to the pre-existing condition. Englebright Dam blocks further impacts from upstream mining waste and is directing the river on a trajectory toward restoration of the pre-existing landform. Daguerre Point Dam serves as a stabilizer in the system, providing a base level for how far incision can go between it and Englebright Dam. Mechanized re-working of alluvium and associated channelization have dictated the lateral bounds of what the river can do now and also impact the diversity and distribution of river-corridor landforms.

In summary, the fluvial geomorphology of the Yuba River is so unique that it is crucial to evaluate it on its own terms and not apply simple generations and concepts from other rivers with dams. Hydraulic mining, dredger re-processing of the valley floor, mechanized in-channel mining, upstream watershed management choices, and dams all combine to yield a system that requires careful investigation before making conclusions about how the fluvial geomorphology works and what restoration opportunities exist.

Recent studies have helped clarify the current status of the river and more investigations are on-going.

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Figure 1.1. Location map of the Englebright Dam Reach (black box) in the Yuba catchment.

Figure 1.2. 1905 photo of the LYR near Parks Bar taken by G.K. Bilbert

(http://libraryphoto.cr.usgs.gov/photo_all.htm).

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Figure 1.3. Dredger forming high tailings berm out of a mining-waste point bar at Rose

Bar on 10/21/1937. (Photo from the California Transportation State Archive).

Figure 1.4. Photo of a gold mining operation on Sinoro Bar circa 1960. (Photo courtest of Ralph Mullican).

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1.2. LYR Salmonids History

1.2.1. Historical Population Accounts

The spring run of Chinook salmon (SRCS) is a federally threatened species that is differentiated by the time at which adults migrate from the ocean to freshwater systems

(Yoshiyama et al. 1996). There are no quantitative estimates for pristine, historic salmonid populations on the Yuba River prior to hydraulic gold mining, let alone isolating just SRCS, but Yoshiyama et al. (1996) reported historic accounts suggesting a large population, possibly in the hundreds of thousands. For example, they cite

Chamberlain and Wells (1879) as stating that the Yuba was so full of salmon that Indians speared them “by the hundred”. However, during hydraulic gold mining much water was diverted away and the river valley was allowed to fill 20-80’ high with mine tailings. A first-hand account of a miner at Long Bar in the valley stated that the miner’s diet primarily consisted of pancakes and there is no mention of fish at all (Lecouvreur, 1906).

Yoshiyama et al. (1996) reported accounts of the construction of Bullards Bar Dam in

1921-1924 in which it was stated that so many salmon were blocked at the construction location that their carcasses had to be burned. SRCS and steelhead both were known to migrate far up into the North and Middle Yuba Rivers and several miles up into the South

Yuba before reaching potentially impassable waterfalls. However, much of the spawning habitat in the upper watershed was badly degraded by mining debris, sand, and turbidity.

If the SRCS population was in the hundreds of thousands of fish, then the riffles in the canyon where Englebright Dam is located would likely have been used by part of that large population during the mining era and early 20th century. However, relative to the total abundance, this number of fish spawning in the canyon may not have drawn the attention of naturalists at the time, especially given the difficulty of getting to that area.

During the latter half of the 20th century, Yuba River salmonid populations were estimated quantitatively (Fig. 1.5), but it is still difficult to isolate SRCS numbers.

Yoshiyama et al. (1996) cite several estimates of the fall-run Chinook salmon population, but provide no enumeration of SRCS. They cite John Nelson as reporting that fall- and spring-run populations are mixed and that these mixed fish are now present in “minimal numbers”. CDFG (1991) enumerates the annual estimate of fall-run Chinook salmon, CORPS 29838 with a range of 1000 in 1957 to 39,000 in 1982. For SRCS, CDFG (1991) states that a remnant population exists and that it is composed of some in-river natural reproduction, strays from the Feather River, and restocked, hatchery-reared fish. Restocking of fingerlings and yearlings was done in 1980. CDFG (1991) reported that 20 pairs of

Chinook salmon were observed to spawn at the Narrows powerhouse in autumn 1986 and due to passage barriers in the autumn, it was decided that these were SRCS that migrated during high spring flows. CDFG stopped conducting annual escapement surveys in 1989.

No survey was done in 1990. The Yuba County Water Agency (YCWA) sponsored

Jones and Stokes, Inc. to perform escapement surveys using the CDFG methodology for

1991-2004.

For 2005-2007 CDFG took over the effort again, but beginning in 2008 the responsibility shifted to the Yuba Accord River Management Team (RMT) as part of its new Monitoring and Evaluation Plan. The RMT’s 2008 escapement and redd reports used temporal modalities associated with fresh carcass observations and frequencies of redd observations to try to differentiate spring- and fall-run Chinook salmon. However, it was not possible to obtain a clear distinction and all data were analyzed together. In all of these modern enumerations, abundance estimates did not isolate SRCS or the subpopulation of all Chinook in the EDR; carcass counts were not made in the EDR due to challenging accessibility.

For March 2007 through February 2008, the RMT operated a Vaki RiverWatcher video monitoring system on both fish ladders at Daguerre Point Dam (~12 miles downstream of the EDR). This system scans the side-view projected area of each fish and takes a color photo of each fish. From these data, staff counts the number of fish that pass and use characteristic morphometrics to identify the species of each fish (for ~70% of individuals). Of the 1,324 Chinook that were observed, 336 (25%) passed in March-

August, which is the period that SRCS likely migrate.

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Figure 1.5. Adult Chinook salmon abundance for the LYR based on carcass surveys and coded-wire tagging.

1.2.2. Physical Habitat Conditions

Physical habitat units in rivers are defined as zones with characteristic attributes where organisms perform ecological functions, which are the ways in which organisms interact with each other and their surroundings. Common attributes of physical habitat include substrate type, water depth, water velocity, water temperature, cover objects, and shading. The quantity and quality of physical habitat are critical factors that can limit the size of fish populations. The assemblage of these attributes stem from the interaction among hydrologic, hydraulic, and geomorphic processes. As a result, when processes are altered or degraded by human intervention, then physical habitat will likely be degraded too. In turn, that decreases the size of fish populations.

Physical habitat conditions related to salmonids downstream of Englebright Dam have been studied over the years. With respect to the spawning life stage, Fulton (2008)

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investigated salmon spawning habitat conditions in the canyon below Englebright Dam and found the conditions to be very poor to nonexistent. No rounded river gravels/cobbles are present in the canyon between Englebright Dam and Sinoro Bar by the confluence with Deer Creek other than a small amount injected artificially in

November 2007. For the whole lower Yuba River, Beak Consultants, Inc (1989) states:

“The spawning gravel resources in the river are considered to be excellent based on the abundance of suitable gravels, particularly in the Garcia

Gravel Pit and Daguerre Point Dam reaches. The tremendous volumes of gravel remaining in the river as a result of hydraulic mining make it unlikely that spawning gravel will be in short supply in the foreseeable future. Armoring of the channel bed is possible, but has not developed to date, probably due to periodic flushing by floods comparable to the 1986 event.”

Similarly, Pasternack (2008) reported that:

In Timbuctoo Bend “…there is adequate physical habitat to support spawning of Chinook salmon and steelhead trout in their present population size. Furthermore, all of the preferred morphological units in the [Timbuctoo Bend Reach] TBR have a lot of unutilized area and adequate substrates to serve larger populations.”

With respect to rearing life stages, Beak Consultants, Inc (1989) states that:

“The Daguerre Point Dam and Garcia Gravel Pit reaches contribute most of the [Weighted Usable Area] WUA, and substantially more than the

Simpson Lane Reach; The Narrows Reach contributes little fry habitat…

Total WUA for juveniles is highest in the Daguerre Point Darn and Garcia

Gravel Pit reaches… The Simpson Lane Reach contributes a small amount of WUA, while The Narrows Reach provides virtually no juvenile habitat.”

Adult migration is presently under study by the RMT, but there are some pre-

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existing observations. Adult SRCS are commonly observed holding in pools in the canyon below Englebright Dam, in the pools in Timbuctoo Bend, and in the pool below

Daguerre Point Dam. In September 2007, UC Davis graduate student Aaron Fulton observed SRCS attempting to dig redds and spawn on bedrock covered with a thin veneer of angular gravel, causing them injury. Acoustic tracking of adult SRCS in 2009 by the

RMT showed that some individuals migrate into and out of the canyon until September at which point they stop migrating and attempt to spawn between Englebright Dam and the highway 20 bridge.

1.3. LYR Geomorphology-Salmonids Nexus

Two key conclusions from this review of previous knowledge are that most of the lower Yuba River is still geomorphically dynamic and that the river possesses a diversity of in-channel physical habitats, even if some types are not as abundant as would be optimal for restoring the size of fish populations that likely existed in the Yuba River prior to the onset of hydraulic gold mining. Hydraulic mining snuffed the river and its floodplain with a vast, homogenous mix of mining waste. Since Englebright Dam blocked that, channel complexity and habitat diversity has been re-emerging, and that process continues. The extent to which it can continue is impacted by the role of the training berms and the degraded state of the entire Yuba Goldfields, both of which are beyond the scope of actions related specifically to the impact of Englebright Dam, which is the focus of this report. The glaring problem in the system associated with this dam is the status of SRCS spawning in the EDR.

The dramatic decline in SRCS in California has been attributed to dams, as they block up to ~80% of historic spawning habitat. Based on life history, impassable high dams have hurt the spawning life stage of adult SRCS the most, because spawning is the purpose behind the migration of SRCS to Sierran headwaters. Under a regulated flow regime, SRCS migrate to bedrock reaches at the base of large dams and hold in pools supplied with cold sub-thermocline water releases. On the Yuba holding occurs below

Daguerre Point Dam and to a lesser extent below Englebright Dam (Fig. 1.6), but once it is time to spawn, SRCS move upstream into the canyon. Therefore, whether they

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provided historically preferred physical spawning habitat or not (and for the Yuba the evidence is that they did), bedrock reaches at the base of large dams play a key role in

SRCS viability under the current regime of impassable dams.

If SRCS cannot spawn in sufficient numbers, then physical habitats supporting their subsequent life stages downstream are irrelevant. There is no question that

Englebright Dam is a complete barrier to fish migration upstream and gravel/cobble transport downstream. Any effort to reinstate SRCS presence upstream of Englebright

Dam would take significant time to figure out, implement, and evaluate its effectiveness.

If such an effort were undertaken, it would still be critical to sustain existing populations below the dam using well-proven methods until passage efforts were equally well demonstrated in the watershed. To achieve usable, preferred SRCS spawning habitat in the canyon, it is necessary to resolve the lack of river-rounded gravels/cobbles there. At this time and for the foreseeable future, only the canyon is in need of a gravel/cobble supply to offset the impact of Englebright Dam.

Figure 1.6. Photo of SRCS holding in bedrock/boulder section of the LYR near the mouth of Deer Creek (photo courtesy of Ralph Mullican).

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2. GRAVEL/COBBLE AUGMENTATION

The key negative impact of Englebright Dam on the lower Yuba River is the loss of a mixture of gravel- and cobble-sized river-rounded rocks in the canyon between

Englebright Dam and the confluence with Deer Creek, which is necessary to support

SRCS spawning there. This reach is known as the Englebright Dam Reach (EDR).

Fulton (2008) investigated physical habitat in the uppermost third of the EDR and found that suitable hydraulics for salmon spawning were present there, but needed substrates were absent (Fig. 2.1). Subsequent modeling of the entire EDR showed that the same holds true for the entire reach- there are areas of good hydraulics, but they lack the needed river-rounded gravel and cobble mixture (Pasternack, 2008a). Thus, the solution to this problem is to implement a procedure known as gravel/cobble augmentation

(Wheaton et al. 2004a; Pasternack, 2008b).

Figure 2.1. Photo of the EDR below Narrows 1 showing the dominance of shot rock on the banks. The wetted channel is devoid of river-rounded gravel and cobble in this area.

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2.1. Gravel/Cobble Augmentation Defined

Gravel/cobble augmentation (aka gravel/cobble injection) is defined as the piling up of coarse sediment (usually a mixture of gravel and cobble ranging in size from 0.3-4 inches (8-100 mm) in diameter) within or along a river (Wheaton et al., 2004a).

The geomorphic goal of gravel/cobble augmentation is to reinstate interdecadal, sustainable sediment transport downstream of a dam during floods, which is necessary to support and maintain diverse morphological units, such as riffles, pools, point bars, and backwaters (Pasternack, 2008b).

The ecological goal of gravel/cobble augmentation that yields self-sustainable morphological units is to have the associated assemblages of physical attributes that are preferred for each of the freshwater life stages of salmonids (Pasternack, 2008b).

Pasternack (2008b) explains the pros and cons of gravel/cobble augmentation relative to other methods of river rehabilitation in support of salmon spawning. It is important to understand that achieving the geomorphic goal does not mean that the ecological goal will be achieved too. It has frequently been observed that when gravel is injected into a river, it just settles into the bottom of a deep in-channel pit or pool, never to be re-entrained. Unless a reach is investigated for its hydrogeomorphic mechanisms of fluvial landform maintenance, then there is no basis to an assumption that ecological benefits will necessary be achieved from successful redistribution of injected coarse sediment. This is the concept of “process-based” river restoration (Beechie et al., 2010).

Any action may or may not work, depending on whether its usage has been placed into the context of the fluvial mechanisms at work in the system. Augmentation of flow or gravel/cobble in the absence of an understanding of processes and impacts is a gamble of unknown value or harm (Pasternack, 2008b).

When performing gravel/cobble augmentation it is often possible to place the material into the wetted channel according a specific design capable of yielding immediate salmon spawning habitat (Wheaton et al., 2004b; Elkins et al., 2007). It can

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be beneficial to add large wood and boulders during construction to form hydraulic structures in symphony with the gravel/cobble placement (Wheaton et al., 2004c).

Together, these diverse elements are shaped (but not hard-wired) to provide adult holding habitat proximal to high-quality spawning habitat, further enhance spawning habitat with complex gravel oxygenation and shading conditions, and furnish early rearing habitat before fish migrate or are flushed downstream. Depending on site history and the specific goals and methods of such efforts, this approach of blending gravel/cobble placement and hydraulic structure construction can dramatically enhance or rehabilitate morphological units and sub-unit hydraulic complexity for a reach below a dam (Elkins et al., 2007). By coupling that with a long-term gravel/cobble injection program at the base of a dam and evaluation of the flow regime, a comprehensive framework for rehabilitating and managing a regulated river can be achieved (Pasternack 2008b). Such a framework for river rehabilitation is hierarchical, because it incorporates a) microhabitat diversity to provide preferred local conditions to support different life stages of existing populations, b) geomorphically sound mesohabitats that provides more and larger organized areas to grow populations, and c) flow variability and injections of gravel to provide the physical inputs necessary for geomorphic dynamics that renew and sustain a gravel-bed river.

2.2. LYR Pilot Gravel/Cobble Augmentation

The United States Army Corps of Engineers (The Corps), UC Davis, and USFWS collaborated on an experimental gravel/cobble injection below Englebright Dam (in the pool below the Narrows II powerhouse) in November 2007. The purpose of this experiment was to find out if and where gravel/cobble would deposit in the EDR and thus gain insight into the efficacy of gravel/cobble injection as a habitat enhancement tool for spring-run Chinook salmon in the EDR. The basic study design involved injecting gravel/cobble during low flow in autumn of 2007 and then waiting for high flows in subsequent water years to move it. Then it would be possible to track where those materials went.

Five hundred short tons of triple washed river gravel/cobble was purchased from a

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nearby quarry downstream. Based on bucket tests in a quarry, Merz et al. (2006) reported a dry bulk density of gravel/cobble to be ~0.722 yds3 per short ton for a Mokelumne

River quarry. Using this estimate, a total of 361 yds3 of gravel/cobble was available to be injected in the EDR. The material was trucked in ahead of time and piled on top of the gravel parking lot at the Narrows II powerhouse (Fig. 2.2). Gravel/cobble injection took place on November 29, 2007 beginning at 9:30 am and finishing by 3:00 pm (Fig. 2.3).

A TB 135 truck-mounted gravel conveyor was used to reach out over the river and inject gravel into the Narrows II pool. A single small loader was used to transfer piled gravel/cobble into the hopper, but it turned out that not all the gravel/cobble could be fully injected during the single allotted day using that one loader. Consequently, a small amount ended up being incorporated into the parking lot, instead of going into the river

(Fig. 2.4). Using a tape measure, the volume of gravel/cobble left behind on the parking lot, in between boulders on the edge of the lot, and spilled over the side was estimated to be ~34 yds3. Thus, ~327 yds3 of gravel and cobble was placed into the river.

As the material was being placed into the river, ~400 painted, magnetized tracer stones were put into the hopper with the gravel/cobble to facilitate tracking. Those tracers are thus integrated all throughout the in-river gravel/cobble pile. Those stones are traceable using a magnetic locator, but any rounded gravel that is found downstream in the EDR must be coming from this source, because there is virtually no other such material in this reach.

Pasternack (2009) investigated the status of the injected gravel/cobble after two winters, and some interesting lessons were evident. Although the two intervening winters were relatively dry (Fig. 2.5), some transport did take place. Of the 327 yds3 that was successfully injected to the river, only ~3 yds3 moved during the period when flow was ≤

8014 cfs. After a flood with a peak flow of 15381 cfs, a total of ~75 yds3 moved. That amount includes the ~3 yds3 that was moved prior to that, so that means that ~252 yds3 remained in the gravel/cobble injection pile in the Narrows II pool as of July 1, 2009.

For the 2010 water year, the peak discharge occurred in June 5, 2010 and it was only

6928 cfs.

Preliminary observations of Chinook salmon redds in 2009-2010 by the RMT found that 120 redds were located in the EDR between September 7, 2009 and February

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22, 2010. This response to limited gravel injection indicates that if more gravel was present, a population of SRCS could be accommodated.

Figure 2.2. 500 short tons of gravel/cobble prior to injection into the Narrows II pool.

Figure 2.3. Gravel injection on November 29, 2007. Gravel pile is located in zone of aeration downstream of the Narrows II powerhouse.

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Figure 2.4. Photo of stockpiled gravel/cobble left on the parking area and hillside after the 2007 pilot injection.

Figure 2.5. EDR Hydrograph of 2008-2009 water years showing flow peaks and the timing of key activities.

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2.3. Methods for Gravel/Cobble Augmentation

Once a decision is made to perform gravel/cobble augmentation relative to other possible actions (Pasternack, 2008b), then it is necessary to determine how to implement

it. Several reports have analyzed different methods for implementing gravel/cobble augmentation downstream of dams on rivers. Kimball (2003) described methods, limitations, horizontal placement distance, discharge rate, and the price per ton for 1,000 tons of gravel/cobble placed using helicopters, cable ways, and various conveyor belt systems (portable, truck-mounted, crane mounted and attached to dump truck). Bunte

(2004) took a different approach and focused on the diverse river forms made with gravel/cobble-augmentation deposits through active construction and “passive” injection.

Those included hydraulic structures, big flat plateaus of gravel, supplementation and lengthening of existing riffles (either upstream or downstream of crest), long riffles with

1-3 crests, artificial spawning channels, complex river patterns, filling of pools, bar shaping, spot fixing. She also covered placement of emergent deposits for future flood redistribution, including dumping along the streambank and construction of ephemeral wing dams directing flow into irrigation diversion canals (Bunte, 2004). Sawyer et al.

(2009) reported a thorough analysis of the opportunities and constraints of using front loaders to place gravel/cobble according to a detailed design.

The environmental assessment report for the 2007 pilot gravel/cobble injection analyzed three methods of gravel/cobble augmentation (USACE, 2007). For the remote canyon downstream of Englebright Dam, there is a tremendous challenge to get down to the water’s edge in the section where gravel is needed most. The alternatives considered were road construction, helicopter, and truck-mounted conveyor belt.

2.3.1. Road Construction and Gravel Placement

The first method assessed by USACE (2007) was gravel/cobble placement by hauling material in 10-ton and 20-ton trucks down to the river’s edge, pouring it along the edge, and distributing it with front loaders. However, the EDR has not had a road down to the water’s edge since the 1997 flood destroyed the previous one there. The elevation

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of the river’s water surface at 855 cfs is ~292’ (NAVD88 datum), whereas the elevation of the end of the existing road at the Narrows II facility is ~353’. The vertical drop of 61’ takes place over a horizontal distance of just ~100’, so the slope is 0.5 (50%). As a result, the road would have to be steep with switchbacks. It would be unlikely for 20-ton trucks to negotiate the switchbacks, so delivery would be limited to 10-ton trucks or front loaders. Moreover, to construct a new road would require importing a large quantity of road fill materials. USACE (2007) raised a serious concern about the risk of these materials eroding by rain, landslide, or flood, which would cause harmful mud, sand, and angular crushed rock to enter the river and integrate into the bed material. USACE

(2007) also indicated that it would be extremely costly and environmentally harmful to remove a temporary road after gravel/cobble augmentation. It is not possible to remove a road off a steep rocky hillside without causing debris to be left behind risking water quality and river-substrate problems. Further considerations in 2010 raised the concern over possibly having to excavate the end of the road in the channel, which could cause water quality problems. Also, the permitting process for road construction would take a long time, precluding gravel/cobble augmentation in 2010 and possibly 2011.

Assuming that a road was constructed and gravel/cobble were to be placed by front loaders, then a suite of concerns related to these machines come into consideration

(Sawyer et al., 2009). Extra care would be necessary to avoid oil or gas leaks out of the machinery (a problem known from other efforts). There is also a limitation in matching grading plans in that front loaders cannot go into water deeper than ~2-2.5’ or else the transmission can be flooded, ruining the machine (another problem known to have happened in the past on another river). Finally, front loaders cause a high level of turbidity as they drive over the river bed, which can be a water quality problem. For all the above reasons, the method of direct gravel/cobble placement commonly used on the

American, Mokelumne, and Trinity Rivers in California is not preferable.

2.3.2. Helicopter Delivery

The second method assessed by USACE (2007) was helicopter delivery. This can be the only means possible for extremely remote locations. However, this approach is the

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most expensive method, it has a slow delivery rate (depending on how far the stockpile is from the placement site), and it involves highly risky helicopter flying in the presence of power lines and in a narrow canyon with variable winds.

2.3.3. Truck-Mounted Conveyor Belt

The third method assessed by USACE (2007), which was ultimately used in the

2007 pilot project, was a truck-mounted conveyor belt. For this approach, a 135’ long conveyor belt mounted onto a truck is fully extended and rotated perpendicular to the truck so that its end is over the river. With a ~100-120’ bank width, this length is just sufficient to get material into the Narrows II pool. Material is fed into a hopper using a small 0.5- to 1-ton front loader, and then a feeder with a conveyor belt lifts the material up and onto the truck-mounted belt that delivers it out over the water. By pouring the gravel/cobble into a deep pool, particle breakage is avoided. The experience with using this method in 2007 was highly positive. The only lesson learned from the 2007 pilot project that would enhance future usage of this method was that gravel/cobble injection would have been faster if two loaders had been used instead of one.

Unfortunately, there are two serious problems with using the truck-mounted conveyor belt approach in 2010 and beyond below Englebright Dam. First, given the geometry of the road, hillside, channel, and Narrows II powerhouse, the area of the wetted channel suitable for injection that is within the 135’ length of the conveyor belt is very limited. Gravel/cobble is not permitted to be injected up against the powerhouse and any pile cannot interfere with the immediate outflow jet issuing from the powerhouse. The Narrows II pool is ~15’ deep, but much of it is not reachable with the conveyor belt. Based on visual appearance at the end of the injection in 2007, the gravel/cobble pile was ~ 11’ high off the bed. Given some more rotation capability and making the water even shallower, it looked like a total amount of <1000 tons could be stored in the pool by this method. The gravel/cobble deficit for the EDR (to be enumerated below in section 3) is one to two orders of magnitude higher than that, making this approach inadequate for the need.

Second, there is a proven concern of gravel/cobble injected into the Narrow II

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pool depositing into the shallow area between the Narrows II and Narrows I powerhouses

(Pasternack, 2009). The gravel/cobble injected in 2007 fractionated by size during transport in 2008-2010, such that coarser material deposited on the first bedrock plateau and finer material deposited further downstream. Spawning has been observed on the shallow coarser material on the bedrock plateau. A potential exists in emergency situations where gravel may be de-watered.

When Fulton (2008) and Pasternack (2008a) evaluated the scour potential in the

Narrows II pool for different sized floods, they assumed that the gravel/cobble would be in a blanket at the bottom of the pool, not standing ~11’ high in a loose conical pile.

They had no knowledge at the time of their efforts in 2005-2006 how gravel/cobble augmentation might be done at remote Englebright Dam, so they made a basic assumption about it. As a result, they studied a very different situation from what ended up happening. For the case of a blanket fill on the bed, they predicted that any flood capable of scouring the bottom of this deep pool would easily transport the material beyond the Narrows I powerhouse. The reason is that the intervening channel area consists of a bedrock plateau that is narrower and shallower over the whole flow range, so that focuses flow into the fastest, most scouring jet of water possible for the EDR.

Based on 2D modeling, it was demonstrated that any flow that could scour gravel/cobble off the bed of the deep pool would definitely be able to transport it beyond the Narrows I facility.

In fact, the actual conditions associated with the 2007 pilot (and any such gravel/cobble augmentation using the truck-mounted conveyor belt) as well as the flow regime that occurred in 2009 were quite different from what had been investigated. Not only was the gravel/cobble piled high unlike in the model simulations, but another important factor not considered was that the Narrows I powerhouse was releasing 500 cfs perpendicular to the channel during the 2009 peak flow overtopping Englebright Dam.

Fulton (2008) did not have a topographic map all the way down to Narrows I for his model study and did not investigate the impact of a flow jetting across the riverbed at that location. Conceptually, such a jet would be expected to dramatically reduce bedload transport past that location.

Thanks to the use of a real-world pilot experiment, Pasternack (2009) observed

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that the 2009 flood of 15381 cfs scoured off the top ~23% of the 2007 pile. None of the eroded material made it past the Narrows I powerhouse. Instead, it deposited in the nooks in bedrock fractures and behind boulders and bedrock outcrops in a narrow band down the length of the area between the two powerhouses. In autumn 2009 Chinook salmonids were observed by RMT staff to be spawning on that material.

Pasternack (2009) provides a thorough evaluation of what happened and the consequence is that injection of a large amount of gravel/cobble into the Narrows II pool would certainly yield deposits in the area between the powerhouses that is at risk for annual dewatering in September-November. Given that the entire EDR is lacking in gravel/cobble, there are other areas where gravel could be introduced downstream of

Narrows I, thereby avoiding the problem if channel dewatering. At a later time it might be worthwhile to revisit the issues related to gravel augmentation upstream of the

Narrows I powerhouse to determine any conditions under which gravel/cobble could be added there to expand total habitat capacity and gravel/cobble storage in the reach.

2.3.4. Dumping Gravel/Cobble off Roadside

Although not discussed in USACE (2007), another option is that gravel/cobble may be added to a stream by dumping it off a truck down a hillside to the stream bank or into a stream (Bunte, 2004). This approach has been used on Clear Creek, Trinity River, and the upper Sacramento River. It is very inexpensive and fast. However, this approach only serves geomorphic and ecologic goals if the material avoids breakage and actually becomes entrained into the river. Normally that requires a flood to achieve, which could be years to decades before it happens, precluding ecological benefits. For the hillside below Englebright Dam, the only section accessible by truck is between Narrows I and II powerhouses raising the potential problem of material depositing on the bed at risk of dewatering.