Abstract Title

Session S-03G: Ecosystem Services and Impacts of Sediment for Salish Sea Recovery

Proposed Abstract Title

Marsh Sediment Retention in the Sediment-Rich Skagit and Sediment-Deficient Nisqually River Deltas

Keywords

Shorelines

Location

Room 6E

Start Date

30-4-2014 3:30 PM

End Date

30-4-2014 5:00 PM

Description

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.

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Apr 30th, 3:30 PM Apr 30th, 5:00 PM

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.