Quantifying Changes in Water Levels and Storm Effects November 7, 2011

1. Vulnerability and Resilience of Coastal Estuaries and Community Infrastructure to Climate Change Quantifying Changes in Water Levels and Storm Effects November 7, 2011 Joe Hamman, Research Assistant Dept. of Civil and Environmental Engineering University of Washington Alan F. Hamlet, Research Assistant Professor JISAO/CSES Climate Impacts Group Dept. of Civil and Environmental Engineering, University of Washington

2. Project Goals • Sea Level • Quantify sea-level rise downstream of estuaries • Explore relationships between PNW regional sea level and observed global climate patterns • Hydrology • Simulate hydrologic changes upstream of estuaries • Describe changes in runoff and flood behavior • Impacts on Estuaries • Combine hydrologic and sea level changes to quantify estuarine water levels and occurrences of flooding, inundation, and other high/low water extremes

3. Project Plan • Hydrologic Modeling • Use naturalized flows developed by the Variable Infiltration Capacity Model (VIC) for the Columbia Basin Climate Change Scenarios Project • Reservoir Modeling • Simulates flood control operations at major reservoirs • Hydrodynamic Modeling • Combine regulated flows with daily sea level predictions to simulate water surface elevations along the lower river • Integrate with GIS based digital elevation models to quantify extent of flooding and inundation • Statistical / Regression Based Model • Develop simple regression relationships between atmospheric variables and predicted regulated floods to simulate estuarine water elevations Hydrology Sea Level Hydrologic Model (VIC) Harmonic Tidal Predictions Meteorological Regression Model Reservoir Operations Model Impacts Hydrodynamic Models Statistical / Regression Model

4. Predicted Hydrologic Changes • Change in Dominant Run-off Timing • Mixed Rain and Snow Basins experience higher flows in fall/winter months and reduced flows in spring/summer months** • Snow dominant basins transition towards hydrographs resembling present day mix rain and snow basins • Increased Flood Magnitudes • Mean estimated future 100 year flood is about 30% higher than the historical (Skagit at Mt. Vernon, A1B) • 98% confidence that Q100 will increase Snow Dominant Mixed Rain and Snow

5. Observed Sea Level Changes • Local Sea Level Change • Observed Rates: ±2 mm yr-1 • Negative rates explained by crustal deformation • Global Sea Level Rise (IPCC AR4) • 1961-2003: 1.8 ± 0.5 mm yr-1 • 20th Century: 1.7 ± 0.5 mm yr-1 • Global Trends Sea Level • PNW experiencing global average Global Sea Level Rise Church et al., 2004 IPCC 2007

6. Predicted Sea Level Changes • UW CIG for Puget Sound • Low Prob. / High Impact: • 55 cm by 2050 • 128 cm by 2100 • High Prob. / Low Impact: • 8 cm by 2050 • 16 cm by 2100 • IPCC scenario based projections • Daily Sea Level calculated using: • Harmonic constants (NOAA) • Regression analysis to predict anomalies data from Hunter, 2010 Sea Level, Seattle, WA

7. Putting it all together • Incorporate hydrology and sea level models into existing hydrodynamic models • USGS • DELFT2D/3D • USACE/FEMA • HEC-RAS / FLO-2D • Use models to investigate • Changing river dynamics • Impacts of larger flood magnitudes and sea level rise

8. Other Angles • Examine coincidence of flooding and high tides • Using the “synthetic” future climates, develop joint probability distributions that describe the likelihood of coincident flooding and high tides. • Role of global climate patterns, such as ENSO, in regional sea level • Can we make inferences on future climates by observing past El Nino years? Theoretical joint probability of exceedence (10 %-90 %). Loganathanet al., 1987

9. What’s left to do? • Complete Nisqually Reservoir Model • Develop time series approximations of historical and future sea level near study estuaries • Incorporate hydrology and sea level models into existing hydrodynamic models • Validate models using water levels measures within the tidally influenced estuaries • Quantify flooding / inundation using GIS approach

10. THANK YOU • QUESTIONS?

11. Study Stats • Skagit River • 3,000 sq. mi., 5 major reservoirs operated by Seattle Public Utilities and Puget Sound Energy • Nisqually River • 750 sq. mi, 2 major reservoirs operated by Tacoma Power • Historical Scenario • Based on observed temperature and precipitation data • Climate Change Scenarios • A1B – Represents unconstrained growth • B1 – Represents rapid growth with an ecological focus • Climate Models • Echam5 climate model for 2040s and 2080s

12. Observed Hydrologic Changes • April 1 SWE has predominantly decreased: • Most dominant in mixed snow-rain basins, • Upward trends are generally due to increased precipitation, • When changes in temperature are isolated, nearly all trends are negative, • PNW SWE decreases 0.14% yr-1 from 1916 to 2003. • Freshwater inflow has changed over the period 1948-2003: • Total annual inflow declined 13 percent, • Snowmelt timing shifted earlier by 12 days (2.1 days per decade), • The fraction of annual flow entering Puget Sound during the summer months decreased 18 percent. Hamlet, 2005 Snover et al., 2005

13. Observed Hydrologic Changes