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Nisqually Delta Sediment Budget & Transport Dynamics

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Presentation given by: Eric Grossman, USGS

Presentation given by: Eric Grossman, USGS

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  • 1. 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
  • 2. How do physical processes redistribute sediment and organicsto shape marshes, channels, nearshore/tidal flats?
  • 3. Tides/HydrodynamicsFish, Substrate,Invertebrates (food-prey)Elevation, Vegetation,Water Quality
  • 4. Conceptual Model and MethodsMethods:1. GIS-Based “RAP” Model2. Hydrodynamic Model lost3. Field Measurements Sediment Delivery
  • 5. 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
  • 6. 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
  • 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 properlyTidal channel currents wellmodeled for portions of thetidal cycle. Roughness(vegetation) not properlycharacterized, yet!
  • 10. Role of vegetation onhydrodynamics & sedimentinformation need
  • 11. Modeled Connectivity 1-Month time period, Avg river discharge: 70 m3/s
  • 12. 3. Field Measurements - Methods Fluvial Inputs River Discharge, Sediment Load (2-yrs; 15-min) Nearshore Hydrodynamics Tides, Currents, Turbidity (2-yr, 3-mo; 5-min) WL 1 3 Currents, SSC, X-Sections (Synoptic: tides, Qw) WL WL WL WL
  • 13. 3. Field Results: Fluvial inputs, WY2011
  • 14. 3. Field Results: Fluvial inputs, WY2011 Fines (silts and clays) ~48% of total load
  • 15. 3. Field Results: River-Marsh Connectivity Marsh Turbidity mean = 0.19 River Turbidity River Turbidity Marsh Turbidity
  • 16. 3. Field Results: Channel Velocities, Discharge
  • 17. 3. Field Results: Channel Discharge McAllister -10.1 cms Small Net Flow in (1.6 cms, <6% river) Area1 2.1 cms 2.1 1.1 3.1 2.2 Madrone 10.1 1.1 cms Leschi 3.1 cms Area3 2.2 cms
  • 18. 3. Field Measurements: Nearshore Sediments & Flux Suspended sediment tracks ~1:1 with turbidity Nearshore turbidity 20-50% of river
  • 19. 3. Field Results: Channel Sediment Flux Net Flux into Marshes (370 m3/yr) Potential Accretion ~0.12mm/yr 2.1 1.1 3.1 2.2 10.1 0.12 mm/yr
  • 20. Vulnerability? Cumulative Impacts? Adaptive Management? 44M m3 of sediment since 1945 (14-70x annual load)
  • 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
  • 22. Nearshore Response: Sand export Photo=Jul 2011 Mapping Aug 2012 50m
  • 23. Nearshore Response: Sand exportMcAllister CreekJul 2009 Jul 2010 Leading edge Sand bar incision Leading edge
  • 24. “Functional” Channel Habitat – Salinity Gradients
  • 25. “Functional” Channel Habitat – Salinity high tide 2 hrs into ebb River Salt Wedge
  • 26. 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
  • 27. “Green” Infrastructure: Coastal habitats to buffer impacts Example, Stillaguamish Delta 1964  Low  Marsh   Low  Marsh  Boundary   Boundary   1964   2004   2012 Restoration
  • 28. GCM-RCM Dynamic Downscaling: Hydrology, Sediment Variable Infiltration Capacity (6km)ECHAM5* & CCSM3 (A1B, A2) WRF DHSVM (100m2)
  • 29. 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)
  • 30. Adaptive Management Opportunity?Simulated levee breach
  • 31. Model Results – Mud Deposition
  • 32. http://coastalresilience.org
  • 33. 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)
  • 34. egrossman@usgs.gov Western Washington UniversityAny interested students please contact EricCoastalresilience.orgSalishsearestoration.org
  • 35. 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)

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