Marsh Sediment Retention in the Sediment-Rich Skagit and Sediment-Deficient Nisqually River Deltas
Presentation Abstract
An integrated modeling and monitoring study of sediment routing through the Skagit and Nisqually River Deltas reveals that tidal marshes in both systems are highly vulnerable to impending sea level rise. Despite significant differences in fluvial sediment loading, transport dynamics, and the influence of waves and nearshore processes that determine the amount of sediment that is retained within the intertidal delta, sediment is largely routed away from marshes to offshore, deeper environments or lacking connectivity to marshes, both because of land use. Sediment is vital to construct coastal land topography of sufficient surface elevation to facilitate formation of tidal channels, marshes, and riparian-covered berms which are critical to salmon recovery goals. Sediment has pronounced influence on seagrass habitat, juvenile chinook nearshore rearing and residency patterns, and benthic invertebrate food prey resources. Interestingly both the Skagit (high sediment load) and the Nisqually (low sediment load due to sediment trapping by Lake Alder) share similar processes that limit tidal marsh accretion, channel development and nearshore function. Historical disconnection of these rivers from their floodplains and distributaries has led to significant sediment export offshore to deeper habitats and reduced connectivity to marshes important to salmon recovery. This presentation will summarize research and modeling results on sediment budgets, retention, and transport pathways and their influence on salmon and estuary restoration objectives today and under a range of scenarios of projected future sea level rise and sediment delivery related to climate change.
Session Title
Session S-03G: Ecosystem Services and Impacts of Sediment for Salish Sea Recovery
Conference Track
Shorelines
Conference Name
Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)
Document Type
Event
Start Date
30-4-2014 3:30 PM
End Date
30-4-2014 5:00 PM
Location
Room 6E
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Sediment transport--Washington (State)--Skagit River Delta; Sediment transport--Washington (State)--Nisqually River Delta
Geographic Coverage
Skagit River Delta (Wash.); Nisqually River Delta (Wash.); 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
Marsh Sediment Retention in the Sediment-Rich Skagit and Sediment-Deficient Nisqually River Deltas
Room 6E
An integrated modeling and monitoring study of sediment routing through the Skagit and Nisqually River Deltas reveals that tidal marshes in both systems are highly vulnerable to impending sea level rise. Despite significant differences in fluvial sediment loading, transport dynamics, and the influence of waves and nearshore processes that determine the amount of sediment that is retained within the intertidal delta, sediment is largely routed away from marshes to offshore, deeper environments or lacking connectivity to marshes, both because of land use. Sediment is vital to construct coastal land topography of sufficient surface elevation to facilitate formation of tidal channels, marshes, and riparian-covered berms which are critical to salmon recovery goals. Sediment has pronounced influence on seagrass habitat, juvenile chinook nearshore rearing and residency patterns, and benthic invertebrate food prey resources. Interestingly both the Skagit (high sediment load) and the Nisqually (low sediment load due to sediment trapping by Lake Alder) share similar processes that limit tidal marsh accretion, channel development and nearshore function. Historical disconnection of these rivers from their floodplains and distributaries has led to significant sediment export offshore to deeper habitats and reduced connectivity to marshes important to salmon recovery. This presentation will summarize research and modeling results on sediment budgets, retention, and transport pathways and their influence on salmon and estuary restoration objectives today and under a range of scenarios of projected future sea level rise and sediment delivery related to climate change.
