Presentation Abstract

The abundance of tidal wetlands has been increasingly impacted by environmental changes, human alterations and sea-level rise around the world. Elevation and sediment dynamics control tidal wetland vegetation colonization, assemblages, resiliency, and recovery trajectories. Seal level rise and hydromodifications may threaten the resiliency of existing tidal marshes, and impact the recovery trajectories of restoration projects. The Snohomish river delta currently supports the second largest extent of tidal wetlands in the Puget Sound, and has become the focus of what could be the largest cumulative estuary restoration effort in Puget Sound. However, we currently know very little about elevation and sediment dynamics in the Snohomish River estuary and the resiliency of existing vegetated marshes and restoration projects. To address this need, we installed surface elevation tables (SETs) and marker horizons (MHs) in 2013-2014 inside several tidal marsh complexes that represent a gradient of land use histories and recovery trajectories to determine sediment accretion rates and shallow soil processes (e.g., subsidence, compaction, uplift) in the Snohomish River estuary. SETs and MHs were installed in two emergent marshes in the lower estuary that have not been previously diked, inside Ebey Island where dikes failed naturally about 75 years ago, and inside a restoration site that was breached in 1994. Preliminary data from these SETs and MHs indicate that accretion rates range from 4-15 mm per year, and that shallow subsidence is occurring at all sites at a rate of 2-10 mm per year. Although continued long-term monitoring will provide better estimates of elevation and sediment dynamics at these sites and within the Snohomish River estuary, we use these preliminary data to evaluate tidal marsh resiliency and recovery trajectories within the context of sea level rise and restoration in the Snohomish River estuary.

Session Title

Estuarine Climate Change Adaptation

Keywords

Surface elevation table, Snohomish river

Conference Track

SSE5: Climate Change: Impacts, Adaptation, and Research

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE5-264

Start Date

6-4-2018 11:15 AM

End Date

6-4-2018 11:30 AM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

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Apr 6th, 11:15 AM Apr 6th, 11:30 AM

Using surface elevation tables and marker horizons to evaluate resiliency and trajectories of tidal marshes and restoration projects in the Snohomish River estuary

The abundance of tidal wetlands has been increasingly impacted by environmental changes, human alterations and sea-level rise around the world. Elevation and sediment dynamics control tidal wetland vegetation colonization, assemblages, resiliency, and recovery trajectories. Seal level rise and hydromodifications may threaten the resiliency of existing tidal marshes, and impact the recovery trajectories of restoration projects. The Snohomish river delta currently supports the second largest extent of tidal wetlands in the Puget Sound, and has become the focus of what could be the largest cumulative estuary restoration effort in Puget Sound. However, we currently know very little about elevation and sediment dynamics in the Snohomish River estuary and the resiliency of existing vegetated marshes and restoration projects. To address this need, we installed surface elevation tables (SETs) and marker horizons (MHs) in 2013-2014 inside several tidal marsh complexes that represent a gradient of land use histories and recovery trajectories to determine sediment accretion rates and shallow soil processes (e.g., subsidence, compaction, uplift) in the Snohomish River estuary. SETs and MHs were installed in two emergent marshes in the lower estuary that have not been previously diked, inside Ebey Island where dikes failed naturally about 75 years ago, and inside a restoration site that was breached in 1994. Preliminary data from these SETs and MHs indicate that accretion rates range from 4-15 mm per year, and that shallow subsidence is occurring at all sites at a rate of 2-10 mm per year. Although continued long-term monitoring will provide better estimates of elevation and sediment dynamics at these sites and within the Snohomish River estuary, we use these preliminary data to evaluate tidal marsh resiliency and recovery trajectories within the context of sea level rise and restoration in the Snohomish River estuary.