Nisqually Watershed Stewardship Plan: Status Report 2018 Draft Presentation
Nisqually Delta Sediment Budget & Transport Dynamics
1. Nisqually Delta Sediment Budget & Transport Dynamics
to Inform Restoration and Climate Change Planning
Eric Grossman, U.S. Geological Survey
Guy Gelfenbaum,
Andrew Stevens,
Chris Curran,
Steve Rubin,
Mike Hayes
PCMSC, WAWSC Nisqually Indian Tribe
WERC, WFRC
2. How do physical processes redistribute sediment and organics
to shape marshes, channels, nearshore/tidal flats?
4. Conceptual Model and Methods
Methods:
1. GIS-Based “RAP” Model
2. Hydrodynamic Model
lost
3. Field Measurements
Sediment
Delivery
5. 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 lost
Sediment
20-100K TY Czuba et al. 2011
4.5-23.0K m3/yr 20-100k TY
USGS, 1974; This study
6. 1. “Rapid Assessment Protocol” - Potential Sediment Accretion
Distribute sediment load scaled by transport connectivity
Data Needs:
1. Sediment load
2. Topography (DEM) lost
3. Tidal Data
11-28%
Grossman and Horne (in prep)
20-100K TY
4.5-23.0K m3/yr
7. 1. “Rapid Assessment Protocol” - Potential Sediment Accretion
Distribute sediment load scaled by transport connectivity
lost
11-28%
20-100K TY Grossman and Horne (in prep)
4.5-23.0K m3/yr
8. 2. Process-based hydrodynamic & sediment transport model
Delft3D couples:
wave - current
interaction
FLOW WAVES
2 or
Bathymetry
3D
TRANSP BOTTOM
Sediment transport (van Rijn, 1993)
Dynamic Morphology
Wetting drying
Vegetation – momentum
(Baptist, 2005; Uittenboogaard, 2003)
~20-30 m grid resolution in
the restoration area
9. 2. Delft3D hydrodynamic & sediment transport model
Tidal forcing well characterized
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!
21. Nearshore Response: Extensive channel incision
Feb 2009 Aug 2011
25 m
2m
1-2 m of incision
10-40 m widening
2009 ~5 km of channels
Sediment
2011 redistributed
367,500 m3
28. Climate Change and Sea Level Rise
Winds/Waves
Observations
following maximum
model prediction
Lower rate due
to wind stress?
Rate ~3.75 mm/yr (2x the 20th century
Will sea level rise
Marshes and coastal habitats response?
accelerate if it
Brominski et al. 2011 relaxes?
IPCC. 2007; Church and White, 2011
31. Projected Climate Impacts to Sediment Delivery
Increase and earlier Seasonal sediment transport model
seasonal runoff
4
2080s
Sediment Load (MT/month)
Curran and Grossman (In Review)
3
Increase
in
flood
and
sediment
2
1
2010
0
Hamlet and Grossman (in prep)
36. 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)
37. egrossman@usgs.gov
Western Washington University
Any interested students please contact Eric
Coastalresilience.org
Salishsearestoration.org
38.
39. Simulated
Flood
Event
Modeling
Approach – Fine
Sediment
Dispersal
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)