South San Francisco Bay Shoreline Studies for EIA 11 with Project Conditions

Transcription

1 South San Francisco Bay Shoreline Studies for EIA 11 with Project Conditions U.S. Army Corps of Engineers San Francisco District Ms. Lisa Andes Mr. Craig Conner Dr. Frank Wu Dr. Jen-Men Lo Dr. Michael MacWilliams Dr. Chia-Chi Lu Dr. Robert Dean US Army Corps of Engineers BUILDING STRONG

2 Project Site Focus Area 2

3 Project History Funds received/fsca signed/project Start October 2005 May 2010 Modeling of without project conditions to support Feasibility Scoping Meeting (FSM) September - December 2010 FSM held, HQ comments resolved, and approved to continue project November February 2011 Project re-scoped (reduced size) October 2011 Switched hydrodynamics model June 2012 Most technical work completed and Decision Making Conference held March st Draft of Feasibility Report & EIS/EIR April 2013 Preparing for the Alternative Formulation Briefing with HQ USACE

4 Project Sponsors

5 Technical Team Dr. Frank Wu Co Technical Manager USACE, San Francisco District Dr. Jen-Men Lo Co Technical Manager Santa Clara Valley Water District Dr. Michael MacWilliams Hydrodynamic Modeling Delta Modeling Associates, Inc. Dr. Chai-Chi Lu Statistical Analysis/Monte Carlo Simulation Noble Consultants, Inc. Mr. Brian Hubel / Dr. Nick Malasavage Levee Failure USACE, San Francisco District Dr. Robert Dean Technical Review University of Florida Mr. Craig Conner Flood Risk Manager USACE, San Francisco District

6 Water Surface Elevation (feet, NAVD88) Project Purpose YR0 NED - Water Surface Elevation at Point 3 1. Flood Risk Management Estimate a combined fluvial and coastal design water surface elevation for levee construction 2. Ecosystem Restoration include in wetland restoration alternatives in design water surface elevation Flood Stage Frequency Curve (Risk and Uncertainty Based Approach) Return Period (years) Expected Value 90% Confidence Limit (5% & 95% Confidence Level) South San Francisco Bay

7 Project Challenges 1. Lack of site specific water surface elevation data at the project site 2. Over 150 years of measured water surface elevation at the San Francisco Tide Station NOAA Tide Stations in the Central and South Bay

8 Coastal Engineering Components Physics (tide, surge wind, wave run-up & over topping, levee stability & fluvial flow) Numerical Modeling (Yr-0 and Yr-50, With- Project Conditions) Statistical Analysis: 1. Extreme Probability Method (EPM) 2. Joint Probability Method (JPM) 3. Monte Carlo Simulation (MCS) Sea Level Rise (NRC Curve III)

9 WSE, NAVD 88 (feet) Tide and Surge Analysis at the San Francisco Tide Station 10 8 Residual Tide ~= 2.4 Measured Tide Predicted Tide Residual Tide Residual Tide and Astronomical Tide are in Phase -2 12/02 12/02 12/03 12/04 12/05 Date (mm/dd/1983)

10 WSE, NAVD88 (feet) Astronomical Tidal Amplification Astronomical Tide is 0 amplified from -2 San Francisco -4 to South Bay 05/16 05/17 05/18 05/19 05/21 Date mm/dd/2011 WSE Measured at Coyote ( ) WSE Measured at San Francisco ( )

11 Residual Tide (m) Residual Tide in the South Bay Approximately no change in residual tide as it propagates to the south bay

12 South Bay Model Grid Model Domain Note: Bathymetry used in grid development was CEPD* compliant *CEPD Comprehensive Evaluation of Project Datums, EM

13 Look-Up Table Outer Levee Proposed Inner Levee 1 Proposed Inner Levee 2 Model Simulations Include: with and without wind and with and without levee failure scenarios Event Tide at San Francisco Astronomical (feet, MLLW) Residual (feet) Evaluation Location

14 Tide (ft) Conditional Sampling Criteria What WSE is justified to be considered as a storm event in extreme coastal and fluvial flood statistics? Measured Tide Predicted Tide Residual Tide 6.9 Feet Above MLLW Scenario Measured Tide >= MLLW (ft) -2 12/01 12/06 12/11 12/16 12/21 12/26 12/31 Residual Tide >= (ft) Date (mm/dd/2002) Number of Events Sampled Rate of Occurrence (Event #/yr) Annual Maximum

15 Flood Stage (ft, MLLW) Extreme Probability Method Return Period (yrs) Gumbel Fit: Measured Tide >= 6.9 & Residual Tide >= 0.0 Gumbel Fit: Measured Tide >= 6.9 & Residual Tide >= 0.5 Gumbel Fit: Measured Tide >= 6.9 & Residual Tide >= 1.0 Gumbel Fit: Annual Maximum Measured Tide (Reference Senario)

16 Probability Probability Probability Probability Probability Distribution Functions Predicted Tide (PDFs) Wind Direction Astronomical Tide, MLLW (feet) Residual Tide Wind Direction ( 0, True North) Wind Speed Wind : o Wind : o Residual Tide (feet) Wind Speed (MPH)

17 Monte Carlo Simulation Process Forcing Functions Astronomical Tide Wind Speed / Direction Residual Tide / Surge Riverine Inflows Fluvial Flow Rate Long Wave Model Short Wave Model Hydraulic Modeling (HEC-RAS) Hydrodynamic Forcing on Levee Breakout Flow Outboard Levee Failure No Fail Fail LWM No Breach LWM w/ Breach No YES No Fail Inboard Levee Failure Fail Basin Flooding Analysis / End Result

18 Water Surface Elevation (feet, NAVD88) Risk & Uncertainty Analysis 12 Water Surface Elevation at Point Return Period (years) Joint Probability Distribution Gumbel Maximum Distribution Expected Value 5% & 95% Confidence Levels

19 Water Surface Elevation (feet, NAVD88) Risk & Uncertainty Analysis 10 Water Surface Elevation at Point 16 9 Effect of Outer Levee Breach: 1. Breach Condition 2. No Breach Condition Expected Value Return Period (years) 90% Confidence Limit (5% & 95% Confidence Level)

20 Water Surface Elevation (feet, NAVD88) Water Surface Elevation (feet, NAVD88) Sea Level Rise Comparison of Water Surface Elevation between Year 0 and Year 50 NRC Curve III Year 0 (2017) Year 50 (2067) 10 Water Surface Elevation at Point Water Surface Elevation at Point Return Period (years) Expected Value 90% Confidence Limit (5% & 95% Confidence Level) Return Period (years) Expected Value 90% Confidence Limit (5% & 95% Confidence Level) WSE between 4.5 and 9.5, feet NAVD88 WSE between 11.3 and 13.0, feet NAVD88 Includes: Sea Level Rise (2.13 feet) and estimated bathymetric change

21 Summary and Conclusions 1. Correct coastal physics associated with tide (predicted and residual) were used 2. The wind set up contribution is negligible 3. MCS provides reasonable estimates of coastal flood stage frequency curve with uncertainty limits 4. MCS, EPM and JPM seem to compare well and demonstrate consistency

22 Next Steps Technical work (including modeling) is currently in the Corps review process ~ July will hold the Alternative Formulation Briefing (AFB) with HQ USACE ~ August September AFB material will be available to the public ~ September 2013 will hold a public meeting on the Administrative Draft Feasibility Report/EIR/EIS ~ June 2014 Report of the Chief of Engineers released ~ 2017 Start of Project Construction* * Pending authorization & appropriations