Khangaonkar Skagit Padilla Bay Hydrodynamic

Sustainable Coastal Habitat Restoration in the Pacific Northwest: Modeling and Managing the Effects, Feedbacks, and Risks Associated with Climate Change

EPA STAR Grant: $100,000 total funding from 2007–2012
Additional funds needed for completion: $50,000

Background and motivation: The Skagit River is the largest and most significant river draining into Puget Sound. The historic Skagit Delta and Estuary is larger than all other Puget Sound estuaries combined. The Skagit River and its estuarine areas form the stronghold of Puget Sound Chinook, recently listed under the Endangered Species Act. The river is also home to one of the most diverse salmonid assemblages in North America.

However, predicted changes may result in considerable impacts to fresh and saltwater ecosystems and the plants, fish and wildlife they support. For instance, recent regional models suggest that summer river flows in the Pacific Northwest are likely to decline by 30% and that the sea level may rise 8 to 30 inches. Such changes will likely affect estuarine vegetation composition and production, impacting salmon restoration and protection efforts.

Local and regional governments and organizations are currently planning for and implementing efforts to protect and recover Chinook salmon populations in the Skagit. This project seeks to create a model that can inform restoration and management efforts. This model will demonstrate the range of possible implications of future sea level rise and other climate change impacts on estuarine rearing habitat for juvenile Chinook.

Padilla Bay

Hydrodynamic Model Grid – Skagit River Estuary with Saratoga Passage and Padilla Bay.

Objective: The overall objective is to develop a model that can predict ecological consequences and likely impacts to the landscape of sea level rise and river flow alteration. This will be accomplished by developing a spatially explicit hydrodynamic and sediment transport model of Padilla Bay and Skagit Bay. The model will be linked to mechanistic wetland elevation dynamics and a vegetation unit model, as well as to models of tidal channel geomorphology and juvenile salmon abundance and distribution.

Project Team: The project team consists of Western Washington University (WSU), Skagit River System Cooperative (SRSC), and Pacific Northwest National Laboratory (Battelle).

Expected outcome (2010): Following calibration and validation, the models will be run under various sea level rise, river flow, and sediment load scenarios. Results can inform revisions of restoration goals and strategies, and of adaptive management responses, depending on how much marsh progradation or erosion occurs over the next century. The study will characterize high– or low-risk restoration sites based on likely vulnerability or resilience to climate change.