Presenter/Author Information

Joelene Boyd, The Nature ConservancyFollow

Type of Presentation

Snapshot

Session Title

Local Stories and Results

Description

The 2012 Port Susan Bay estuary restoration project in the Stillaguamish River delta was designed to restore 150 acres of once marginal farmland to estuary habitat and tidal influence. The expected impact of the dike setback, however, extends beyond the project footprint to the broader estuary. The return of sediment delivery and freshwater input is expected to help restore marsh habitat in the larger estuary and in particular the northern marsh, which has eroded about 21 meters inland per year since the 1960s. After three years of post-restoration monitoring, unprecedented events have led to unexpected results at the project site and larger estuary. The massive Oso Landslide that occurred in March 2014 along the Stillaguamish River significantly increased sediment delivered to Port Susan Bay during the study period. Record low snow pack and warm weather conditions in 2015 resulted in increased water temperatures and unusually high salinities in the estuary, providing a glimpse of projected climate change conditions. Water temperatures in the Stillaguamish River near the restoration project exceeded thermal barriers to adult salmon migration approximately 20% of the time from May to September 2015. Sediment accretion, favorable for restoring marsh habitat, is occurring in some areas while marsh erosion continues in others. Vegetation recruitment in the restoration project is variable with some areas being colonized by native vegetation and bare areas expanding in others. The bird population in the restoration area shifted from one dominated by passerines and freshwater divers to more dabbling ducks. The collective suite of results from the last three years of monitoring at Port Susan Bay tell an interesting story of an estuary restoration project and potential considerations for future restoration projects.

Comments

Key Words:

estuary, restoration, river, delta, monitoring, habitat

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Three Years Later: Port Susan Bay Estuary Restoration Project

2016SSEC

The 2012 Port Susan Bay estuary restoration project in the Stillaguamish River delta was designed to restore 150 acres of once marginal farmland to estuary habitat and tidal influence. The expected impact of the dike setback, however, extends beyond the project footprint to the broader estuary. The return of sediment delivery and freshwater input is expected to help restore marsh habitat in the larger estuary and in particular the northern marsh, which has eroded about 21 meters inland per year since the 1960s. After three years of post-restoration monitoring, unprecedented events have led to unexpected results at the project site and larger estuary. The massive Oso Landslide that occurred in March 2014 along the Stillaguamish River significantly increased sediment delivered to Port Susan Bay during the study period. Record low snow pack and warm weather conditions in 2015 resulted in increased water temperatures and unusually high salinities in the estuary, providing a glimpse of projected climate change conditions. Water temperatures in the Stillaguamish River near the restoration project exceeded thermal barriers to adult salmon migration approximately 20% of the time from May to September 2015. Sediment accretion, favorable for restoring marsh habitat, is occurring in some areas while marsh erosion continues in others. Vegetation recruitment in the restoration project is variable with some areas being colonized by native vegetation and bare areas expanding in others. The bird population in the restoration area shifted from one dominated by passerines and freshwater divers to more dabbling ducks. The collective suite of results from the last three years of monitoring at Port Susan Bay tell an interesting story of an estuary restoration project and potential considerations for future restoration projects.