1. 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

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

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

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

5. 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)

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

7. 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 = ms-1
BC: no flux from the left; free flux at the right

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

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

10. 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

11. 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)

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

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

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

15. South Bay

16. SSC profile at South Bay
2005 Jan
200

17. 200

18. 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?

19. 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.

20. Fluid-mud suspension
Hard bed erosion

21. 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
Erosion
Fluid mud Consolidation
Under Consolidated Bed

22. 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).

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

24. Thank you