Nisqually Delta Sediment Budget & Transport Dynamics to Inform Restoration and Climate Change Planning

Eric Grossman, U.S. Geological Survey

Nisqually Indian Tribe PCMSC, WAWSC WERC, WFRC

Guy Gelfenbaum, Andrew Stevens, Chris Curran, Steve Rubin, Mike Hayes

How do physical processes redistribute sediment and organics to shape marshes, channels, nearshore/tidal flats?

Tides/Hydrodynamics

Fish, Substrate, Invertebrates (food-prey) Elevation, Vegetation, Water Quality

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Sediment Delivery

Conceptual Model and Methods

Methods: 1. GIS-Based “RAP” Model 2. Hydrodynamic Model 3. Field Measurements

Sediment

1. “Rapid Assessment Protocol” - Potential Sediment Accretion

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Distribute sediment load scaled by transport connectivity

Data Needs: 1. Sediment load 2. Topography (DEM) 3. Tidal Data

USGS, 1974; This study 20-100k TY

Czuba et al. 2011 20-100K TY 4.5-23.0K m3/yr

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20-100K TY 4.5-23.0K m3/yr

Grossman and Horne (in prep)

11-28%

1. “Rapid Assessment Protocol” - Potential Sediment Accretion Distribute sediment load scaled by transport connectivity

Data Needs: 1. Sediment load 2. Topography (DEM) 3. Tidal Data

20-100K TY 4.5-23.0K m3/yr

11-28%

Grossman and Horne (in prep)

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1. “Rapid Assessment Protocol” - Potential Sediment Accretion Distribute sediment load scaled by transport connectivity

FLOW WAVES

2 or 3D

TRANSP BOTTOM

Bathymetry

wave - current interaction

2. Process-based hydrodynamic & sediment transport model

Sediment transport (van Rijn, 1993) Dynamic Morphology Wetting drying Vegetation – momentum (Baptist, 2005; Uittenboogaard, 2003)

Delft3D couples:

~20-30 m grid resolution in the restoration area

Tidal forcing well characterized 2. Delft3D hydrodynamic & sediment transport model

Tidal inundation reasonably modeled; some channels not resolved properly

Tidal channel currents well modeled for portions of the tidal cycle. Roughness (vegetation) not properly characterized, yet!

Role of vegetation on hydrodynamics & sediment information need

Modeled Connectivity

1-Month time period, Avg river discharge:

70 m3/s

3. Field Measurements - Methods

Currents, SSC, X-Sections (Synoptic: tides, Qw)

Tides, Currents, Turbidity (2-yr, 3-mo; 5-min)

River Discharge, Sediment Load (2-yrs; 15-min)

Fluvial Inputs

Nearshore Hydrodynamics

1 3

WL

WL

WL

WL

WL

3. Field Results: Fluvial inputs, WY2011

3. Field Results: Fluvial inputs, WY2011

Fines (silts and clays) ~48% of total load

3. Field Results: River-Marsh Connectivity

= 0.19 mean Marsh Turbidity

River Turbidity

River Turbidity

Marsh Turbidity

3. Field Results: Channel Velocities, Discharge

McAllister

Area1

Madrone

Leschi

Area3

-10.1 cms

2.1 cms

1.1 cms

3.1 cms

2.2 cms

3. Field Results: Channel Discharge

Small Net Flow in (1.6 cms, <6% river)

10.1 2.1 1.1 3.1 2.2

3. Field Measurements: Nearshore Sediments & Flux

Suspended sediment tracks ~1:1 with turbidity

Nearshore turbidity 20-50% of river

3. Field Results: Channel Sediment Flux

Net Flux into Marshes (370 m3/yr)

10.1 2.1 1.1 3.1 2.2

Potential Accretion ~0.12mm/yr

0.12 mm/yr

44M m3 of sediment since 1945 (14-70x annual load)

Vulnerability? Cumulative Impacts? Adaptive Management?

Nearshore Response: Extensive channel incision

Feb 2009 Aug 2011

2 m

25 m

2009

2011

1-2 m of incision 10-40 m widening ~5 km of channels

Sediment redistributed 367,500 m3

Nearshore Response: Sand export

Photo=Jul 2011

Mapping Aug 2012

50m

Jul 2010

Sand bar

incision

Leading edge

Nearshore Response: Sand export

Jul 2009

Leading edge

McAllister Creek

“Functional” Channel Habitat – Salinity Gradients

“Functional” Channel Habitat – Salinity

high tide

2 hrs into ebb River

Salt Wedge

Climate Change and Sea Level Rise

Observations following maximum model prediction

Rate ~3.75 mm/yr (2x the 20th century Marshes and coastal habitats response?

IPCC. 2007; Church and White, 2011

Lower rate due to wind stress?

Will sea level rise accelerate if it relaxes? Brominski et al. 2011

Winds/Waves

1964  Low  Marsh  Boundary  

Low  Marsh  Boundary  1964  2004  

“Green” Infrastructure: Coastal habitats to buffer impacts

2012 Restoration

Example, Stillaguamish Delta

GCM-RCM Dynamic Downscaling: Hydrology, Sediment

ECHAM5* & CCSM3 (A1B, A2)

WRF

Variable Infiltration Capacity (6km)

DHSVM (100m2)

Curran and Grossman (In Review)

Increase and earlier seasonal runoff

Seasonal sediment transport model

Projected Climate Impacts to Sediment Delivery

Increase  in  flood  and  sediment  

Hamlet and Grossman (in prep)

2080s

Sedi

men

t Loa

d (M

T/m

onth

)

4

3

2

1

0

2010

Adaptive Management Opportunity?

Simulated levee breach

Model Results – Mud Deposition

http://coastalresilience.org

Flow to marsh = 3-6% of the river Suspended sediment concentrations = 20-50% river Sand exporting from marshes

Potential Accretion Rate: <2 mm/yr (RAP); <0.3 mm/yr (measurements) 2010-2011 river flow was low

Adaptive Management: 1-Alder Lake traps >15x equiv. annual sediment load to delta 2-New Distributary?

Climate Change Adaptation and Resilience 1-Changes in Sediment delivery and fate 2-Sea level rise/waves (erosion, channel salinities) 3-Ecosystem functional response?

Information Needs 1-Interaction of vegetation-hydrodynamics-geomorphology 2-Test fish use of “functional” channels (salinity gradients)

egrossman@usgs.gov Western Washington University

Any interested students please contact Eric

Coastalresilience.org

Salishsearestoration.org

Simulated  Flood  Event  

Investigate three scenarios

1. Flow Only (tides and river flood)

2. Flow and Waves (tides, river flood, and waves)

3. Flow + River Breach (tides, river flood, and river breach)

Modeling Approach – Fine

Sediment Dispersal