Nisqually Delta Sediment Budget & Transport Dynamics to Inform Restoration and Climate Change Planning Eric Grossman, U.S. Geological SurveyGuy Gelfenbaum,Andrew Stevens,Chris Curran,Steve Rubin,Mike HayesPCMSC, WAWSC Nisqually Indian TribeWERC, WFRC
How do physical processes redistribute sediment and organicsto shape marshes, channels, nearshore/tidal flats?
Conceptual Model and MethodsMethods:1. GIS-Based “RAP” Model2. Hydrodynamic Model lost3. Field Measurements Sediment Delivery
1. “Rapid Assessment Protocol” - Potential Sediment Accretion Distribute sediment load scaled by transport connectivityData Needs:1. Sediment load2. 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
1. “Rapid Assessment Protocol” - Potential Sediment Accretion Distribute sediment load scaled by transport connectivityData Needs:1. Sediment load2. Topography (DEM) lost3. Tidal Data 11-28% Grossman and Horne (in prep) 20-100K TY 4.5-23.0K m3/yr
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
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
2. Delft3D hydrodynamic & sediment transport model Tidal forcing well characterized Tidal inundation reasonably modeled; some channels not resolved properlyTidal channel currents wellmodeled for portions of thetidal cycle. Roughness(vegetation) not properlycharacterized, yet!
Role of vegetation onhydrodynamics & sedimentinformation need
Modeled Connectivity 1-Month time period, Avg river discharge: 70 m3/s
“Functional” Channel Habitat – Salinity high tide 2 hrs into ebb River Salt Wedge
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
Projected Climate Impacts to Sediment Delivery Increase and earlier Seasonal sediment transport model seasonal runoff 4 2080sSediment Load (MT/month) Curran and Grossman (In Review) 3 Increase in ﬂood and sediment 2 1 2010 0 Hamlet and Grossman (in prep)
Flow to marsh = 3-6% of the riverSuspended sediment concentrations = 20-50% riverSand exporting from marshesPotential Accretion Rate:<2 mm/yr (RAP); <0.3 mm/yr (measurements) 2010-2011 river flow was lowAdaptive Management:1-Alder Lake traps >15x equiv. annual sediment load to delta2-New Distributary?Climate Change Adaptation and Resilience1-Changes in Sediment delivery and fate2-Sea level rise/waves (erosion, channel salinities)3-Ecosystem functional response?Information Needs1-Interaction of vegetation-hydrodynamics-geomorphology2-Test fish use of “functional” channels (salinity gradients)
email@example.com Western Washington UniversityAny interested students please contact EricCoastalresilience.orgSalishsearestoration.org
Simulated Flood Event Modeling Approach – Fine Sediment DispersalInvestigate 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)