docNumerical Modeling Analysis of the Katrina Cut Rubble Mound
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Numerical Modeling Analysis of the Katrina Cut Rubble Mound
Numerical Modeling Analysis of the Katrina Cut Rubble Mound Structure Gordon Thomson, PE, D.CE Samantha Danchuk, PE, Ph.D. Chris Day, PE Mark Saunders, PE A World of Solutions Outline Project Location History of Breaching Katrina Cut Emergency Structure Risk Assessment and Modeling – Calibration – Inputs – Results Summary A World of Solutions 1 Project Location A World of Solutions 2 Project Location A World of Solutions 3 Project Location Mobile Bay Mississippi Sound Dauphin Island Katrina Cut Pelican Island Petit Bois Island A World of Solutions 4 History of Dauphin Island Breaching 1917 A World of Solutions 5 History of Dauphin Island Breaching 1925 A World of Solutions 6 History of Dauphin Island Breaching 1940 A World of Solutions 7 History of Dauphin Island Breaching February 1992 A World of Solutions 8 History of Dauphin Island Breaching March 2000 A World of Solutions 9 History of Dauphin Island Breaching May 2005 A World of Solutions 10 History of Dauphin Island Breaching June 2006 A World of Solutions 11 History of Dauphin Island Breaching February 2008 A World of Solutions 12 History of Dauphin Island Breaching May 2010 A World of Solutions 13 History of Dauphin Island Breaching September 2011 A World of Solutions 14 Katrina Cut Hurricane Ivan A World of Solutions 15 Katrina Cut 7.5 feet deep A World of Solutions 16 Katrina Cut Katrina Cut A World of Solutions 17 Katrina Cut A World of Solutions 18 Emergency Barrier Emergency barrier constructed during Deepwater Horizon Spill to limit oil flowing into Mississippi Sound Designed and constructed by Thompson Engineering under an emergency permit Rubblemound with sand core ALDOT Class 5 riprap D=2.75 feet, 130pcf Grade “A” riprap D=1.6 feet, 130pcf A World of Solutions 19 Emergency Barrier A World of Solutions 20 Emergency Barrier A World of Solutions 21 Risk Assessment State has requested to leave the structure in place Goal of risk assessment is to provide information to permitting agencies A World of Solutions 22 Risk Assessment Life Cycle Based Analysis – Quantify risks associated with structure • Breaching • Sediment transport • Impact to private property, navigation, SAV, pipelines – Compare with and without structure condition over a 50 year period A World of Solutions 23 Model Input A World of Solutions 24 Model Input 50 year simulations Repeated historic storm record in sequence – 1917 to 1967 – 1960 to 2010 Average conditions based on 20 year WIS record – Non-storm waves were broken into 12 bins Performed using two sea level rise scenarios – USACE guidance for low and high SLR A World of Solutions 25 Model Input Morfac and storm history for 1917 to 1967 A World of Solutions 26 Model Calibration Calibrated for storm response and long-term volumetric change – Repeated Katrina breach – 20 year calibration run Model verification using Hurricane Ivan and Hurricane Isaac – Shoreline and volume changes – Breach width A World of Solutions 27 Model Calibration 2005 LIDAR Survey Delft3D Model Prediction A World of Solutions 28 Model Calibration 20-year Calibration Run 1991 to 2010 Volumetric Change Yellow dots are observed changes Dotted lines are DELFT3D results A World of Solutions 29 Model Results: With Structure A World of Solutions 30 Model Results: With Structure Structure promotes longshore transport initially Breach forms in low lying area adjacent to structure Structure is flanked, cross shore transport dominates A World of Solutions 31 Model Results: With Structure A World of Solutions 32 Model Results : With Structure Eastern end of the dike structure A World of Solutions 33 Model Results: Without Structure A World of Solutions 34 Model Results: Without Structure A World of Solutions 35 Model Results Number of Parcels Private Property (Land) Loss Note – Most likely scenario (more storms, low / observed sea level rise) A World of Solutions 36 Model Results Hurricane Isaac Feet 0.5 0.3 0.2 0 -0.2 -0.3 -0.5 A World of Solutions 37 Model Results A World of Solutions 38 Model Results A World of Solutions 39 Summary Method for 50 year life cycle analysis – Historic storm record – Longer calibration period Specific findings – No breaching along developed section until a major storm event in year 20 – No difference in breaching potential along inhabited area between the with and without structure scenario – Breaching expected adjacent to structure during next major storm – Loss of property indistinguishable between with and without structure (within expected model accuracy) – Future land loss expected regardless of presence of structure A World of Solutions 40 Contact Gordon Thomson, P.E. D.CE Director [email protected] (561) 361-3147 A World of Solutions 41
