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Geomorphic Response of Estuaries to
Sea Level Rise and Climate Change
Bruce Jaffe
U.S. Geological Survey
Pacific Science Center
Santa Cruz, CA
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Explore Geomorphic Response of Estuaries toClimate Change and Sea Level Rise
•• Sediment supply and demandSediment supply and demand–– Historical data and numerical modelsHistorical data and numerical models
•• Limitations of simple modelsLimitations of simple models–– Bruun Bruun rulerule
•• Change in hydrodynamics and sediment transportChange in hydrodynamics and sediment transport–– Numerical modelsNumerical models
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Examples and modeling presented in this talk will focus on San Pablo and
Suisun Bays, twosub-embayments of the San Francisco Estuary
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San Pablo Bay- A prime example of the effects of changing sediment supply
Change from depositional to erosional system
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Intertidal mudflat arearesponded to changesin sediment supply to
San Pablo Bay
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Mudflats widened where sediment was abundant
Jaffe et al., 2007
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Bruun Rule- A simple model
Pilkey and Cooper, 2004
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Conceptual Application of Bruun Rule to San Pablo Bay
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Comparison of Actual and Bruun Rule Deposition and Erosion
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CASCaDE’s Geomorphology Models
Outputs• Depth distribution• Turbidity• Habitat distribution
BDWM/CALSIM• Delta inflows• Magnitude• Timing
ROMS/DELFT3D• Hydrodynamics• Sediment transport • Geomorphology
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Increase in tidal amplitude with 1 m SLR
1 m SLRno SLR
10% increase in tidal amplitude up-estuary
Mick van der Wegen
Delft-3D Model
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Decrease in tidal bottom shear stress
Mick van der Wegen
Delft-3D Model
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Sea-level rise: • Increase in water depth
reduces wave-induced shear stress
• Less erosion, less redistribution
Warming: • Minor changes in redistribution
Decreased sediment supply: • Erosion everywhere except
fringes
Suisun Bay Sea Level Rise and Climate Change ROMS Model
Neil Ganju
ROMS Model
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Summary- Geomorphic Response of Estuaries toSea Level Rise and Climate Change
•• Sediment supply and demandSediment supply and demand–– Historical data and numerical modelsHistorical data and numerical models
• Sediment supply extremely important• SLR will increase sediment demand
•• Limitations of simple modelsLimitations of simple models–– Bruun Bruun rulerule
• Does not predict changes in San Pablo Bay• Limited by being 2D, not a closed system
•• Changes in hydrodynamics and sediment transportChanges in hydrodynamics and sediment transport–– Numerical modelsNumerical models
• SLR increases tidal amplitude• SLR decreases average tidal bottom shear stress in San Pablo Bay• SLR decreases wind wave bottom shear stress in Suisun Bay,
induces deposition in shallows