Carbon River Right Bank Floodplain Connection Project

About the Project

The purpose of the project is to connect Carbon River main channel flows to its floodplain and an existing side channel, located on the right bank side of the river.  The goal is to connect at least six acres of floodplain for a 2-year flow event and stage, using at least six engineered log jams.  The reason for connecting the floodplain is for the benefit and enhancement of fish habitat.  Benefits also include reduction of flow pressure and damage to the opposite left bank side river levee.  


The project is identified and listed as part of the draft Pierce County Habitat Conservation Plan (HCP).  The project will provide fish habitat mitigation credits under the plan and is located in subject reach of the Carbon River that is known to be of high quality habitat and productive for salmonid usage respective to spawning.


Floodplain Connection is accomplished by constructing and placing at least 6 Engineered Log Jams (ELJ) in the main stem close to the Carbon River active channel (3 Apex Jams and 3 Deflector Jams).  Size of ELJ’s varies from large size Apex Jams (approx. 15-Ft x 25-Ft) to smaller size Deflector Jams (approx. 8-Ft x 10-Ft)


Due to river dynamics, rivers are ever changing and can be inherently dangerous places to recreate. River flow combined with natural inputs of sediment, rock, and wood can pose natural hazards to those who choose to recreate on the river. As part of the proposed Carbon River Floodplain Reconnection project, engineered wood structures are incorporated in the design concepts to help manage flows and provide habitat benefits. These structures can pose hazards similar to what are found naturally in river systems.

Contact Us 

Pierce County staff is available to discuss the feasibility study and what it could mean for the area.


Randy Brake, Project Manager

[email protected]


Rob Wenman, Senior Planner [email protected]


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Project Location and Funding
Carbon River RB Project Area Map

Location

Located along the Carbon River Right Bank and adjacent floodplain area between River Miles 3.4 and 4.3, which is north of SR162 and east of 178th Ave. East.


Funding

Local Surface Water Management Fees and Flood Control Zone District will likely provide the majority of the funding.


Funding and schedule for project permitting, design and construction have not yet been identified.



Benefits & Potential Impacts 

Benefits

  • Reduced levee damages and repair costs
  • Reduced flooding impacts
  • Improved fish habitat and water quality

Potential Impacts

  • Existing levee
  • Recreation Fishing/Hiking/Kayaking
  Project Timeline
  • December 2020: Feasibility and Conceptual Alternatives Study
  • April-May 2021: Community and Public Outreach
  • October 2021: Preliminary Design
  • Anticipated in May 2023: Permitting
  • Anticipated Completion in August 2022: Property Acquisition
  • March 2022: Final Engineering Design
  • Anticipated Summer 2024: Construction

  Project Alternatives

Please Review Alternatives A, B, and C below. Each Alternative has Features, Outcomes, and Maps. Click on each Map to review in detail.

  1. Project Alternative A
  2. Project Alternative B
  3. Project Alternative C
  4. Property Tax Parcel Map
InundationExtentsComparison_2year_AA_EC Opens in new windowClick on Map to review in detail
Project Features
  • 6 Engineered Log Jams (ELJs)
    • 3 Deflector Wood Structures
    • 3 Apex Wood Structures
  • 2 pilot channels
  • Lowest construction complexity (location and number of pilot channels and ELJs, permitting)
  • Smallest area of potential disturbance during construction
  • Smallest cost
  • 6 ELJs in main Carbon River channel
Meets main HCP goal
  • Increased inundation in right bank floodplain area
    • Increase of up to 3.6 acres for yearly flows
    • Increase of 7.8 acres at 2-year flow
  • Moderate increase in access to floodplain features for aquatic species
  • Moderate increase in diversity of in-channel wood
  • Small increase in water levels and water velocities along left bank levee
  • Increase in 100-year flood levels in undeveloped portions of 5 private parcels

Next Steps

Community input on the three alternatives is vital to help shape the future of the Carbon River Right Bank Floodplain Connection Project.  A series of open houses, mail notices, surveys and interviews will be available to the community and to those interested or directly impacted by this project. Based on evolving social distancing guidelines from local, state, and federal public health agencies, open houses and other outreach may take place online throughout this project. We will share the most up to date information here as it is available. 


The results of the study will be finalized and made public.