Restoration of the Yankee Fork Salmon River

Sponsored by:Shoshone-Bannock Tribes (Jeff Anderson)

Idaho Department of Fish and Game (Tom Curet)

USDA Forest Service (Kerry Overton; Tom Montoya)

University of Idaho (John Buffington; Peter Goodwin)

Statement of the problem• Snake River chinook salmon, steelhead, and bull trout have been

listed under the Endangered Species Act as threatened, and westslope cutthroat trout are a Forest Service Sensitive Species.

• Severe population decline of Snake River Chinook salmon has resulted from hydropower operations on the Columbia and Snake Rivers (CBFWA 1991), overharvest, introduction of exotics and hatchery fishes, and habitat degradation (Nehlsen et al. 1991).

• Until passage problems are resolved, the resiliency and persistence of remaining wild salmon stocks will be largely dependent on the quality and diversity of remaining stream habitats (Lee et al. 1997).

Yankee Fork

Historic records indicate that the Yankee Fork of the Salmon River was a particularly productive subbasin for salmonids (Overton et al. 1999) and has been classified as critical habitat for chinook and steelhead (57 FR 14653; 62 FR 111).

Dredge mining

• A 6 mile reach of the mainstem Yankee Fork has been severely altered by dredge mining.

• The dredged reach has been straightened, simplified, and isolated from its floodplain and is no longer capable of supporting a naturally functioning riverine ecosystem, and has been identified in Section 4.4.1.a of the Salmon Subbasin Summary as a major limiting factor.

Limiting factors

1. Rearing habitat

2. Spawning habitat

3. Spatial connectivity of quality habitat

The dredged reach limits the productivity and biological function of the basin by reducing and degrading the available:

1. Rearing habitat

Wide shallow flow, lack of riparian shading, and lack of bed and bank irregularities create temperature extremes that inhibit growth and survival during rearing.

1. Rearing habitat cont.

Simplified channel form in the dredged reach also creates high velocities and a lack of hiding places (undercut banks, pools, etc.) which likely decrease survival during rearing.

2. Spawning Habitat

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West Fork

Dredge

What limits spawning habitat?

Lack of adult holding areas due to simplified channel morphology (lack of pools) and high velocities.

Simplified morphology, high velocities, and extreme temperatures also may decrease survival to emergence and successful rearing, thereby decreasing the number of return spawners to the dredged reach.

These processes may have elevated sediment loads, possibly degrading spawning and rearing habitat.

Sediment supply

Lowering of the channel base-level during dredge mining has destabilized side slopes adjacent to the channel and may have initiated knick-point propagation (channel incision) along Yankee Fork tributaries.

3. Spatial connectivity

Recent studies indicate that linkages between salmonid populations and spatial distribution of habitats may be a crucial component of ecosystem health and basin viability (Rieman and Dunham 2000).

The dredged reach fragments the remaining quality habitat in the basin (Overton et al. 1999).

The valley slope, position within the watershed, and historic records indicate that the dredged reach was probably prime rearing and spawning habitat in an otherwise steep, mountain drainage basin. Consequently, the dredge mining effectively removed a significant portion of an already limited amount of salmonid habitat within the Yankee Fork basin.

Restoration

A multi-year restoration plan is proposed to reclaim the historic spawning and rearing habitat within the dredged reach and to reconnect the remaining quality habitat, thereby increasing the biological integrity of the basin.

Identify physical and biological linkages to better define restoration actions and potential.

Examine the larger spatial and temporal watershed processes and conduct restoration that is likely to be successful given the imposed watershed conditions.

The restored channel is expected to have a pool-riffle morphology, narrower width-to-depth ratio, and a functioning floodplain and riparian zone. These qualities should increase spawning and rearing success by reducing velocities, reducing excessive sediment transport and bed scour, reducing temperature extremes, increasing channel complexity, increasing oxygenation of buried embryos, and minimizing fine sediment deposition within the channel.

Restoration Approach

• Pre-restoration study and design• Phased restoration, allowing iterative

improvement of methods • Long-term physical and biological monitoring

Pre-restoration Study and Design

Successful channel restoration requires a clear understanding of current watershed conditions, how they differ from those of the past, what the desired future conditions are, and how the channel is likely to respond to restoration activity.

Here, we seek to quantify past and current physical and biological conditions to provide a baseline for restoration activities and to provide data necessary to develop restoration options and designs.

Existing Data

• Habitat and spawning surveys since the 1930’s

• Pilot watershed analysis related to Chinook salmon

• Quantification of current and past hydrologic and geomorphic conditions

Data Gaps

• Completion of aerial photography analysis of historic conditions

• Development of spatial coverages (GIS) of existing and historic stream riparian area, channel condition, and floodplain

• Geomorphic watershed analysis, including basin-wide assessment of channel morphology, physical process domains, and sediment budget (sources, magnitudes, and routing of sediment)

Restoration DesignDesign criteria:1) Create a naturally-functioning channel and riparian zone

Methods: Develop regional reference reaches, hydraulic geometry

relationships, and regime diagrams (predictions of stable channel form) to provide initial guidance on channel morphology

Use hydrodynamic models to predict flow and sediment transport within the channel and across the floodplain for a range of typical discharges

Quantify hyporheic processes and the interaction of shallow groundwater with the channel and floodplain

Restoration Design2) Maximize aquatic habitat

Methods: Use hydrodynamic models to rank potential aquatic habitat

for different design options as a function of temperature, velocity, substrate size, and flow depth

Conduct laboratory studies to examine interactions between proposed channel morphology, surface and intergravel flow, and consequent aquatic habitat. Maximize intergravel oxygenation of buried salmonid embryos, and minimize sedimentation and deposition of fine particle sizes within potential spawning sites.

Phased Restoration• Restore natural channel characteristics and floodplain function

Grade, redistribute, and/or remove dredge spoils Construct new channel(s) and cross-section alignment Install restoration features (wood debris, bioengineered

banks, etc.)• Restore riparian plant communities

Plant seedlings, transplant trees/shrubs Install erosion control fabric and seed

• Improve design and implementation based on results of concurrent monitoring

Physical and Biological MonitoringFactors to be monitored:• Aquatic habitat, fish usage, and species abundance (Platts et al.

1983; Overton et al. 1995; 1997)• Water quality (toxins and bio-accumulation of heavy metals)• Stream temperature• Surface and subsurface sediment size (Church et al. 1987;

Bunte and Abt 2001)• Channel topography and plan form• Hydraulic discharge (Nolan et al. 1998)• Sediment transport (Emmett 1980)• Riparian vegetation• Shallow groundwater and hyporheic processes

Restoration Performance

• Conduct statistical analyses of changes in physical and biological conditions

• Compare different techniques for restoration implementation in terms of their success, cost, and time involved in implementation

Knowledge Transfer

• Involve local high schools in data collection and restoration activities

• Participate in community and stakeholder meetings

• Develop agency reports • Author and present study results at scientific

conferences and in peer-review publications

Expected Outcomes

• A naturally-functioning riverine ecosystem• Improved spawning and rearing habitat• Reconnection of fragmented habitat and

increased biological integrity of the basin

Questions?