Haffner-Barfuse Floodplain Restoration Project

King County retained WSE and Herrera Environmental Consultants to evaluate the hydraulic and geomorphic effects of proposed levee and revetment setback along the Snoqualmie River near Fall City, WA that is aimed at restoring salmonid habitat and maintaining or improving existing flood hazard protection. The proposed restoration design involves allowing the river to migrate, reconnecting floodplains and side channels, thus creating a more dynamic and diverse fluvial environment.

Role/Services:

  • Predicting the geomorphic trajectory of the reach following project completion
  • 2D modeling of  the hydraulics of the proposed project design
  • Ensuring that the proposed restoration design both generates diverse riverine habitat and protects surrounding infrastructure and property.

Outcome: The project is ongoing. To date, WSE has conducted studies of hydraulics, bank migration, wood dynamics, and historical channel evolution along the Lower Snoqualmie. This research has informed predictions and identified key uncertainties regarding geomorphic change expected to result from the proposed design and has iteratively informed revisions to that design. Combining geomorphic analyses and hydraulic modeling, WSE has helped evaluate how proposed design elements influence both habitat gains and potential risks. Moving forward, WSE will conduct further geomorphic and hydraulic studies to address existing uncertainties and provide important context needed to further refine the restoration design.