Nisqually Delta Sediment Budget & Transport Dynamics

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Presentation given by: Eric Grossman, USGS

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Nisqually Delta Sediment Budget & Transport Dynamics

  1. 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. 2. How do physical processes redistribute sediment and organicsto shape marshes, channels, nearshore/tidal flats?
  3. 3. Tides/HydrodynamicsFish, Substrate,Invertebrates (food-prey)Elevation, Vegetation,Water Quality
  4. 4. Conceptual Model and MethodsMethods:1. GIS-Based “RAP” Model2. Hydrodynamic Model lost3. Field Measurements Sediment Delivery
  5. 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. 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. 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. 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. 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. 10. Role of vegetation onhydrodynamics & sedimentinformation need
  11. 11. Modeled Connectivity 1-Month time period, Avg river discharge: 70 m3/s
  12. 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. 13. 3. Field Results: Fluvial inputs, WY2011
  14. 14. 3. Field Results: Fluvial inputs, WY2011 Fines (silts and clays) ~48% of total load
  15. 15. 3. Field Results: River-Marsh Connectivity Marsh Turbidity mean = 0.19 River Turbidity River Turbidity Marsh Turbidity
  16. 16. 3. Field Results: Channel Velocities, Discharge
  17. 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. 18. 3. Field Measurements: Nearshore Sediments & Flux Suspended sediment tracks ~1:1 with turbidity Nearshore turbidity 20-50% of river
  19. 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. 20. Vulnerability? Cumulative Impacts? Adaptive Management? 44M m3 of sediment since 1945 (14-70x annual load)
  21. 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. 22. Nearshore Response: Sand export Photo=Jul 2011 Mapping Aug 2012 50m
  23. 23. Nearshore Response: Sand exportMcAllister CreekJul 2009 Jul 2010 Leading edge Sand bar incision Leading edge
  24. 24. “Functional” Channel Habitat – Salinity Gradients
  25. 25. “Functional” Channel Habitat – Salinity high tide 2 hrs into ebb River Salt Wedge
  26. 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. 27. “Green” Infrastructure: Coastal habitats to buffer impacts Example, Stillaguamish Delta 1964  Low  Marsh   Low  Marsh  Boundary   Boundary   1964   2004   2012 Restoration
  28. 28. GCM-RCM Dynamic Downscaling: Hydrology, Sediment Variable Infiltration Capacity (6km)ECHAM5* & CCSM3 (A1B, A2) WRF DHSVM (100m2)
  29. 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. 30. Adaptive Management Opportunity?Simulated levee breach
  31. 31. Model Results – Mud Deposition
  32. 32. http://coastalresilience.org
  33. 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. 34. egrossman@usgs.gov Western Washington UniversityAny interested students please contact EricCoastalresilience.orgSalishsearestoration.org
  35. 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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