Environmental Fluid Mechanics Laboratory Three-Dimensional Hydrodynamic Modeling of Sediment Transport in San Francisco Bay Using SUNTANS By Yi-Ju Chou Collaborators: Sueann Lee, Vivien Chua, Oliver Fringer, Jeff Koseff, Stephen Monismith Environmental Fluid Mechanics Laboratory Stanford University http://stanvonog.com/?tag=oceanbeach

Outline Motivation Model Framework Hydrodynamic Validation Sediment Module Development Preliminary Results Future Work

Motivation Development of a calibrated 3D SF-Bay sediment predictive and diagnostic tool for -- Ecological restoration -- Climate change -- Contaminant transport -- Management issues

Model Framework Stanford Costal Ocean Model – SUNTANS Features -- Unstructured grid -- Wetting and drying -- High-resolution transport scheme

Hydrodynamics Validation Grid resolution: horizontal 200 m in average; 50 m minimum 60 vertical layers (minimum dz = 0.9 m) Date: Jan 1st 2005~Jan 30th 2005 Open boundaries: Pacific Ocean & Sacramento-San Joaquin Delta Data source: bathymetry – National Geophysical Data Center fresh water inflow – DAYFLOW program (CDWR 1986) tidal forcing – 8 major tidal constituent measured at Fort Point (Courtesy by Vivien Chua)

Hydrodynamics Validation Point San Pablo Benicia Dashed: SUNTANS predictions Solid: observations

Sediment Module: Non-cohesive Sand Sediment bottom BC: mass flux = Pk – Ws Cb Channel Case Validation Domain: 40,000 m x 100 m x 10 m (Initial) (L x W x H) Grid: 400 x 2 x 20 Time step: 15 s Total time: 48,000 x 15 Ws = -0.002 ms-1 BC: no flux from the left; free flux at the right

Time = 15 s Time = 90 s Time = 210 s Time = 435 s Time = 735 s Time = 1200 s

Temporally Averaged Normalized Concentration Profiles: C/Ca Black dashed: Rouse curve Colored: model results Ca: concentration near the bottom C Ca

Sediment Module: Cohesive Sediment (Mud) Flocculation settling Water column Particle hindering Deposition Resuspension Weak fluid mud Erosion Consolidation Fluid mud Erosion Consolidation Consolidated bed Erosion Consolidation

Consolidation, T, (g m-2s-1) Parameter Setup (following Lee et al, ECM 2003) Layer thickness (mm) Dry density (kg m-3) τce for erosion (N m-2) Erosion rate, E0, (g m-2s-1) α in erosion Consolidation, T, (g m-2s-1) 180 450 600 750 900 0.10 0.41 0.45 0.47 0.52 0.03 0.02 6.5 0.001 0.002 25 50 1000 Settling velocity = f(c) Layer number = 5 (1~5 in SUNTANS) 10,000 mg L-1 ws Erosion (Parchure & Mehta,1985): 10 mg L-1 180,000 mg L-1 C Consolidation: Bottom shear stress: τ = τc + τw (US Corps of Engineers)

U (m/s) SSC (mg/L) Jan 5th 2:00 2005 Jan01 1200 Jan 5th 4:00

Jan 5th 8:00 SSC (mg/L) Jan 5th 10:00 Jan 5th 12:00

Jan 5th 14:00 SSC (mg/L) Jan 5th 16:00 Jan 5th 18:00

South Bay

SSC profile at South Bay 2005 Jan05 1200 200

200

Work Summary SUNTANS-SED-SFBay features -- Unstructured -- Wetting and drying -- High resolution transport scheme -- Validated hydrodynamics for Jan 2005 -- Multi-layer mud bed -- Non-uniform sediment bed structures -- Simple wave model (US Corps Engineers) Simulation Results -- SSC sensitive to settling velocity -- SSC less than field measurement; wave forcing?

Model Challenge: 1. Sediment Properties In-situ sediment properties measurement -- Erosion rate -- Critical shear stress -- Flocculation, hindering, settling velocity -- Missing properties of mud layers Sedflume Data Report San Francisco Bay Mudflats Sea Engineering, Inc.

Fluid-mud suspension Hard bed erosion

Model Challenge: 2. Non-uniform Wind Field Balance of wave action density (e.g SWAN) Significant wave height Wave orbital velocity: Ub Radiation stress Deposition Resuspension Stationary suspension (high conc.) Real-time SF Bay wind patterns (from http://www.met.sjsu.edu/cgi-bin/wind/windbin.cgi?x=309&y=289) Erosion Fluid mud Consolidation Under Consolidated Bed

Information Gap Sediment-water interface Proper boundary conditions for sediment erosion and deposition. In-situ measure on mud layers. Parameterization of small-scale bedforms (sand bed).

Acknowledgement Mark Stacey, UC Berkeley Dave Schoellhamer, USGS Sacramento California State Coastal Conservancy

Thank you