Interim Report Interim Interim Report - Ike Dike Concept for Reducing Hurricane Storm Surge in the Houston-Galveston Region Bruce A. Ebersole, Thomas C. Massey, Jeffrey A. Melby, Sep 2015 Norberto C. Nadal-Caraballo, Donald L. Hendon, Thomas W. Richardson, Robert W. Whalin Jackson State University Jackson State University 1 Contents 1 Overview ............................................................................................................................................................ 3 2 Storm Surge Model Validation for Hurricane Ike ................................................................................................ 6 Introduction ........................................................................................................................................ 6 Computed Maximum Water Surface Elevations for Hurricane Ike ......................................................... 8 Comparison with High Water Marks .................................................................................................... 9 High Water Marks from Gage Measurements of Water Surface Elevation ............................................... 10 Visually Estimated High Water Marks .................................................................................................... 14 3 Texas Coast Historic Hurricanes ...................................................................................................................... 19 Intensity of Historic Hurricanes .......................................................................................................... 19 The September 1900 Galveston Hurricane ........................................................................................ 20 Hurricane Carla ................................................................................................................................ 26 4 The “Bracketing” Set of Hypothetical Synthetic Storms ................................................................................... 31 5 Hurricane Surge Generation on the Open Coast – Causative Factors ............................................................ 36 What Causes a Storm Surge? ........................................................................................................... 36 Wind ..................................................................................................................................................... 36 Atmospheric Pressure ........................................................................................................................... 37 Waves .................................................................................................................................................. 37 Storm Surge along the Texas Coast .................................................................................................. 39 Surge Forerunner .................................................................................................................................. 39 Surge Generation by the Core Winds ..................................................................................................... 49 6 Hurricane Surge Generation within Galveston Bay – Causative Factors ......................................................... 53 Introduction ...................................................................................................................................... 53 Existing Conditions ........................................................................................................................... 54 Surge Generation in Galveston Bay - With the Ike-Dike Concept........................................................ 63 7 Influence of Storm Track on Surge Development ............................................................................................ 73 Introduction ...................................................................................................................................... 73 Forerunner Surge Development as a Function of Storm Track ........................................................... 74 Development of Surge within the Bays Due to Forerunner Propagation and Winds ............................. 86 Galveston Bay Storm Surge Response to the Hurricane’s Core Winds ............................................ 100 8 Reduction in Flooding Achieved with the Ike Dike......................................................................................... 117 Introduction ................................................................................................................................... 117 The Long Dike or Levee Effect ....................................................................................................... 118 Hurricanes of Varying Intensity - The Direct-Hit Set ......................................................................... 119 Major Hurricanes Approaching from the South ................................................................................ 128 Major Hurricanes Approaching from the South-Southeast ............................................................... 137 Major Hurricanes Approaching from the Southeast ......................................................................... 148 Jackson State University 2 9 Placing Hurricane-Induced Water Levels in a Probabilistic Context .............................................................. 155 Introduction ................................................................................................................................... 155 Approach for Statistical Analysis of Water Surface Elevation ........................................................... 156 Joint Probability Analysis .....................................................................................................................157 Joint Probability Method ......................................................................................................................157 Joint Probability Method with Optimal Sampling ...................................................................................160 JPM-OS-BQ Implementation for the Present Study ..............................................................................161 Probability Distributions of Tropical Storm Parameters .........................................................................170 Estimation of Errors and Other Secondary Terms .................................................................................171 Summary of Differences in JPM-OS Studies for the Houston-Galveston Region ....................................175 Existing Condition Water Surface Elevation Statistics ...................................................................... 176 Probabilistic Context for Hurricane Ike’s Maximum Water Surface Elevations .................................. 184 The Proxy Storm Concept .............................................................................................................. 185 Identification and Selection of Proxy Storms ................................................................................... 187 10-yr Proxy Storm ...............................................................................................................................190 100-yr Proxy Storm .............................................................................................................................192 500-yr Proxy Storm .............................................................................................................................194 Proxy Storm Simulations With and Without an Extended Ike Dike ................................................... 196 Effect of the Extended Ike Dike for the 100-yr Proxy Storm ...................................................................197 Effect of the Extended Ike Dike for the 500-yr Proxy Storm ...................................................................199 10 Influence of Sea Level Rise on Storm Surge ................................................................................................ 202 Introduction ................................................................................................................................... 202 11 Summary of Key Findings to Date ................................................................................................................ 204 Generation of the Open Coast Storm Surge ................................................................................... 204 Surge Generation within Galveston Bay ......................................................................................... 204 Influence of Storm Track on Surge Development ............................................................................ 205 Dependence of Peak Surge on Hurricane Intensity ......................................................................... 207 Dependence of Peak Surge on Storm Track ................................................................................... 207 Putting Storm Surge in the Context of Probability............................................................................ 208 Surge Reduction Achieved with the Ike Dike Concept ..................................................................... 210 Results from Original Bracketing Set of Storms and Initial Modeling Approach ......................................210 Results from 100-yr and 500-yr Proxy Storms and Revised Modeling Approach ....................................211