patrick barnard bruce jaffe jeff hansen dan hanes an overview of delft3d modeling of the san...
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Patrick Barnard Patrick Barnard Bruce JaffeBruce JaffeJeff HansenJeff HansenDan HanesDan Hanes
An overview of Delft3D Modeling of An overview of Delft3D Modeling of the the
San Francisco Bay Coastal SystemSan Francisco Bay Coastal System
Edwin Elias and Li EriksonEdwin Elias and Li Erikson
IntroductionIntroduction• USGS interestUSGS interest
• Delft3D Model systemDelft3D Model system
• General introduction into the General introduction into the San Francisco Bay modelSan Francisco Bay model
• Detailed studies:Detailed studies:– Long term ebb-tidal deltaLong term ebb-tidal delta– San Pablo BaySan Pablo Bay– Golden Gate areaGolden Gate area– Ocean BeachOcean Beach– Crissy Marsh InletCrissy Marsh Inlet
IntroductionIntroductionUSGS interest….USGS interest….(1)(1) What are the dominant sediment transport What are the dominant sediment transport pathways?pathways? - San Francisco Bay Coastal System- San Francisco Bay Coastal System - Ocean Beach- Ocean Beach - Dredge disposal sites- Dredge disposal sites - Large sand wave fields- Large sand wave fields - Crissy Marsh Inlet- Crissy Marsh Inlet
(2) Long-term evolution of San Pablo and Suison Bay (2) Long-term evolution of San Pablo and Suison Bay
(3) What is the cause of observed ebb tidal (3) What is the cause of observed ebb tidal delta constriction?delta constriction?
(4) What is the cause of the erosional hot spot (4) What is the cause of the erosional hot spot at Ocean Beach?at Ocean Beach? - Sediment supply?- Sediment supply? - Wave refraction/focusing patterns?- Wave refraction/focusing patterns? - Tidal current patterns?- Tidal current patterns?
Scale Cascade (de Vriend, 1998)
Sand waves Sediment budget ETD
Ocean Beach SF BAY evolution
Modeling Modeling StrategyStrategy
• Use existing tools to do the jobUse existing tools to do the job
• Ability to run this on desktop Ability to run this on desktop computerscomputers
• Selected : Delft3D modeling Selected : Delft3D modeling systemsystem
• Construct a base modelConstruct a base model- Limited in resolution- Limited in resolution- Validated on hydrodynamics- Validated on hydrodynamics- Provides boundary conditions - Provides boundary conditions for detailed studiesfor detailed studies
• Create detailed models Create detailed models for each projectfor each project
• Add complexity where neededAdd complexity where needed
Coastal Morphodynamic Modeling using Delft3D
• Cartesian and spherical co-ordinates
• 2D and 3D (σ or fixed layers in the vertical)
• salinity and temperature
• Online Morphology
• turbulence closure (incl. k-L and k-E) models
• drying and flooding
• sediment and morphology
• Dredging and dumping
• Rain fall and evaporation
• Thermal discharge and heat fluxes
• drogue tracks
• domain decomposition
• Wave – Current interactions
• Particle tracking
• Sediment tracking
Coastal Morphodynamic Modeling using Delft3D
Waves:
• SWAN (40.72)
• XBeach
Processes:
• enhanced bed shear stress
• wave forcing due to breaking
• wave-induced mass flux
• additional turbulence
• wave streaming:
Coastal Morphodynamic Modeling using Delft3D
Multiple sediment fractions
Bed stratigraphy
Transport FormulationsNon Cohesive• Van Rijn
(1984,1993,2004,2010) • Engelund-Hansen (1967) • Meyer-Peter-Muller (1948)
Bijker (1971) • Soulsby/van RijnCohesive• Partheniades & Krone
(default)• Slib3d
Morphological Acceleration:
morphology MOR hydrodynamict f t
FLOW grid
Delft3D Base Model Set upDelft3D Base Model Set up
Single domain model application
Domain Decomposition andDomain Decomposition andschematized Deltaschematized Delta
Domain Decomposition application (25000 cells)
Run time: 1 month 2dh hydrodynamics
1.5 hours (on a 2.66 Ghz Quad Core machine
Domain Decomposition andDomain Decomposition andschematized Deltaschematized Delta
Domain Decomposition application (25000 cells)
Run time: 1 month 2dh hydrodynamics
1.5 hours (on a 2.66 Ghz Quad Core machine
SWAN SetupSWAN Setup
• Four nested grids withFour nested grids with 500 m, 200 m, 100 m, 500 m, 200 m, 100 m, and 25 m resolutionand 25 m resolution
• CDIP buoy #029 data CDIP buoy #029 data used to force model used to force model on 3 open boundarieson 3 open boundaries (2D MEM Spectra)(2D MEM Spectra)
• Current grid generated Current grid generated with Delft3D flow modelwith Delft3D flow model
SF water level
Ocean Beach water level
Dep
th (
m)
MORE validation…..MORE validation…..
cm2/Hz/deg
Velocities at Ocean Beach
Velocities at Crissy Marsh
Swell at Crissy Marsh
IntroductionIntroduction• USGS interestUSGS interest
• Delft3D Model systemDelft3D Model system
• General introduction into the General introduction into the San Francisco Bay modelSan Francisco Bay model
• Detailed studies:Detailed studies:– Long term ebb-tidal deltaLong term ebb-tidal delta– San Pablo BaySan Pablo Bay– Golden Gate areaGolden Gate area– Ocean BeachOcean Beach– Crissy Marsh InletCrissy Marsh Inlet
Long-term morphodynamic predictionsLong-term morphodynamic predictions
Evolution of the San Francisco Ebb Tidal Delta Over the Past Half Century
Observed Depth ChangeObserved Depth Change
WHY has the Ebb Tidal Delta contracted? (and what will happen in the future?)
Several potential causes:
(1) Change in sediment supply2) Rising sea level3) Tidal Prism change in SF Bay4) Increase in Pacific Ocean Waves
Prerequisite: can the model approximately reproduce the observed delta?
Model: Tides only, 50 yrModel: Tides and Waves, 50 yr
Measured 2004/2005
Model-reality consistencies:- Overall shape and orientation Asymmetry- Secondary Flood Channels
Model: T0
Long-term morphodynamic predictionsLong-term morphodynamic predictions
Evolution of the San Francisco Ebb Tidal Delta Over the Past Half Century
Observed Depth ChangeObserved Depth Change
Model: Tides only, 50 yr
Measured 2004/2005
Long-term morphodynamic predictionsLong-term morphodynamic predictions
Evolution of the San Francisco Ebb Tidal Delta Over the Past Half Century
Observed Depth ChangeObserved Depth Change
Model: Tides only, 50 yrModel: Tides and Waves, 50 yr
Measured 2004/2005
Long-term morphodynamic predictionsLong-term morphodynamic predictions
Evolution of the San Francisco Ebb Tidal Delta Over the Past Half Century
Observed Depth ChangeObserved Depth Change
WHY has the Ebb Tidal Delta contracted? (and what will happen in the future?)
Several potential causes:
(1) Change in sediment supply2) Rising sea level3) Tidal Prism change in SF Bay4) Increase in Pacific Ocean Waves
Prerequisite: can the model approximately reproduce the observed delta?
Higher Sea Level > ETD Contraction
Shallower Bay > ETD Contraction
Deeper Bay > ETD Expansion
100 year long simulations with tide only
Hindcasting bathymetric change in San Pablo BayMick van der Weegen (IHE) & Bruce Jaffe (USGS)
Measured: 1877 1856 - 1877
Modeled: 1877 1856 - 1877
Measured: 1856 Measured - Modeled:Residual sediment transport:
Wet period Dry period
Predicted sediment transport - ‘hydrodynamic tidePredicted sediment transport - ‘hydrodynamic tide ’’
Ocean – Bay interactionOcean – Bay interactionUnderstand the processes of flow and sediment Understand the processes of flow and sediment transport in and around the San Francico Bay transport in and around the San Francico Bay
entranceentrance
Predicted mean flow – 1-month periodPredicted mean flow – 1-month period
Predicted flow over the Predicted flow over the sandwave areasandwave area
Hot-spot erosion at Ocean BeachHot-spot erosion at Ocean BeachJeff Hansen (USGS, Santa Cruz)
Fy
S
x
S
yhg
y
vv
x
vu
t
vh by
yyyx
)()(
The Alongshore Momentum Balance
LHS = Advective terms
A= Pressure gradient, g= gravity
B= Radiation stresses
C=Bed shear stress
D=Turbulent momentum flux (Reynolds stresses)
LHS A B C D
LISST
January 2008: collected synoptic sediment samples and CTD-LISST profiles and nearly continuous ADCP current measurements over a spring and neap tide along two transects across the Gate
Flux through the Golden GateFlux through the Golden Gate
Inne
r tr
anse
ct n
eap
tide
Sediments at Crissy Marsh inlet
Net bedload transport over morphodynamic tide
Tide-induced transportTide-induced transport
Wave componentWave component
Forcing: 2.0 m / direction sector
Forcing: 5 m / direction sector
N
S
C
EW
1
5
6
2
3
42
Swell penetration through the Swell penetration through the Golden GateGolden Gate
0o
180o
270o 90o
Boundary forcing Wave focusing past the GG
Swell penetration through the Swell penetration through the Golden GateGolden Gate
SummarySummaryo Models are available that can address sediment transports in SF Bay
on a variety of spatial and temporal scales.
o Ocean-bay interaction is critical for understanding sediment transport within San Francisco Bay ; You need to model bay – ocean – and probably the delta to get it right….
o Currently, sediment transport is inferred from fairly well validated hydrodynamics; for true calibration and validation of models, there is an urgent need for sediment transport and morphologic change measurements
o However….it is not that simple…..
o Changes in morphology are usually small; hence you need a look over a long-time frame to get a “realistic” estimate.
o Modeling over these long-time frames is difficult especially if forcing processes and physical setting are complex.
o Short term modeling can be more accurate, but instantaneous sediment measurements are costly, usually limited to a few locations, and inaccurate.
Future DirectionsFuture Directions
• (better) Quantify (better) Quantify sediment flux through sediment flux through the Golden Gatethe Golden Gate
• 3D Modeling3D Modeling
• San Francisco Bay San Francisco Bay Coastal System Coastal System sediment budgetsediment budget
http://walrus.wr.usgs.gov/coastal_processes/http://walrus.wr.usgs.gov/coastal_processes/
Future DirectionsFuture Directions
http://walrus.wr.usgs.gov/coastal_processes/http://walrus.wr.usgs.gov/coastal_processes/
• Calibrate and validate a Calibrate and validate a coupled ocean-bay-delta coupled ocean-bay-delta model (unstructured)model (unstructured)
• Operational (real-time/now Operational (real-time/now cast) modelcast) model
• Use beyond sediment…..Use beyond sediment…..– Search and RescueSearch and Rescue– Track and Trace (e.g. oil spills)Track and Trace (e.g. oil spills)– Rapid assessment model for Rapid assessment model for
disasters disasters – Flood predictionFlood prediction