Nisqually River Delta Habitat Restoration

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Reducing flooding through nature-based solutions

Increasing climate impacts are threatening the health of the Nisqually River Delta and the fisheries it supports. USGS research concluded that Interstate 5 is exacerbating flood and habitat impacts by restricting flow where it crosses the delta.

Rethinking the Nisqually Corridor

While the Washington State Department of Transportation (WSDOT) has launched the I-5 Marvin Rd to Mounts Rd project to protect the portion of I-5 crossing the Nisqually River Delta, the Nisqually Indian Tribe is partnering with Long Live the Kings and others to seek more comprehensive nature-based solutions to improve key salmon habitat.

These solutions present an opportunity to reduce future flooding impacts and increase climate resilience. By acting now, the Nisqually Indian Tribe has a once in a generation opportunity to ensure benefits from this planned bridge redesign flow back to them and deliver a breadth of ecosystem and community resilience benefits which will serve the tribe for decades to come.

Potential nature-based solutions to be completed include:

Developing side channels to improve water distribution and create forested riverine habitat

Planting native species to create habitat for wildlife and to reduce erosion

Placing large woody debris to reduce water speed and improve sediment delivery in the river delta

Historic realignment of McAllister Creek to increase emergent marsh habitat and improve resiliency

A Flood Event Waiting To Happen

Flooding events are growing in both intensity and frequency

While flooding along the Nisqually River is a natural phenomenon, USGS research forecasts that these flooding events are growing in both intensity and frequency due to climate-driven weather changes and sea level rise.

This is a significant threat to the vital salmon habitat prized by the tribe, with flooding events that reduce habitat function and harm salmon.

It also threatens the Nisqually Wildlife Refuge and the tribe’s homes and infrastructure, including the Nisqually Indian Reservation and important Nisqually Indian Tribe landmarks. The USGS study also predicts an extreme flood event overtaking I-5 by 2040, posing enormous risks to a vital piece of regional infrastructure.

Further, the study concluded that Interstate 5 is exacerbating flood impacts by restricting flow where it crosses the delta via the Nisqually Bridge. This constrained configuration of the Nisqually River mainstem leads to flow that was likened to a “fire hose,” disrupting the movement of water and sediment.

Project Impact

250

Acres Covered

8%

Reduction of acres flooded

7,400+

Acres that could benefit

6 inches

Reduction of flood water levels

Project Partners

Project Contact

Keith Estes

Project Manager (he/him/his)

206.382.9555 x33

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