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Wave Runup and Overtopping FOCUSED STUDY REPORTS WAVE RUNUP AND OVERTOPPING Wave Runup and Overtopping FEMA Coastal Flood Hazard Analysis and Mapping Guidelines Focused Study Report February 2005 Focused Study Leader Chris Jones, P.E. Team Members Ida Brøker, Ph.D. Kevin Coulton, P.E., CFM Jeff Gangai, CFM Darryl Hatheway, CFM Jeremy Lowe Ron Noble, P.E. Rajesh Srinivas, Ph.D., P.E. FOCUSED STUDY REPORTS WAVE RUNUP AND OVERTOPPING Table of Contents 1 INTRODUCTION........................................................................................................................1 1.1 Categories and Topics..................................................................................................... 2 1.2 Wave Runup and Overtopping Focused Study Group.................................................... 3 1.3 Current FEMA Guidance for Wave Runup and Overtopping ........................................ 3 1.3.1 Introduction .......................................................................................................... 3 1.3.2 Wave Runup ......................................................................................................... 4 1.3.3 Wave Overtopping ............................................................................................... 5 2 CRITICAL TOPICS ....................................................................................................................9 2.1 Topic 12: Review Appropriateness of Using Mean vs. Higher Values for Runup and Overtopping ................................................................................................................... 9 2.1.1 Description of the Topic and Suggested Improvement ........................................ 9 2.1.2 Description of Procedures in the Existing Guidelines.......................................... 9 2.1.3 Application of Existing Guidelines to Topic—History and/or Implications for the NFIP ............................................................................................................. 10 2.1.4 Alternatives for Improvement ............................................................................ 12 2.1.5 Recommendations.............................................................................................. 14 2.1.6 Preliminary Time and Cost Estimate for Guideline Improvement Preparation. 14 2.1.7 Related Available and Important Topics............................................................ 14 2.2 Topic 11: Review Runup Methods and Programs; Provide Explicit Guidance on Where Each Should Be Applied .................................................................................. 14 2.2.1 Description of the Topic and Suggested Improvement...................................... 14 2.2.2 Description of Procedures in the Existing Guidelines ....................................... 15 2.2.3 Application of Existing Guidelines to Topic—History and/or Implications for the NFIP ............................................................................................................. 16 2.2.4 Alternatives for Improvement ............................................................................ 16 2.2.5 Recommendations.............................................................................................. 29 2.2.6 Preliminary Time and Cost Estimate for Guideline Improvement Preparation. 29 2.2.7 Related Available and Important Topics............................................................ 30 3 AVAILABLE TOPICS ...............................................................................................................30 3.1 Topic 49: Review WRUPTM (Available Wave Runup Program) ................................ 30 3.1.1 Description of the Topic and Suggested Improvement...................................... 30 3.1.2 Description of Procedures in the Existing Guidelines ....................................... 30 3.1.3 Application of Existing Guidelines to Topic—History and/or Implications for the NFIP ............................................................................................................. 30 3.1.4 Alternatives for Improvement ............................................................................ 30 3.1.5 Recommendations.............................................................................................. 30 3.1.6 Preliminary Time and Cost Estimate for Guideline Improvement Preparation. 30 3.2 Topic 13: Develop Improved Guidance for Determining and Mapping Overtopping Volumes ....................................................................................................................... 31 3.2.1 Description of the Topic and Suggested Improvement...................................... 31 3.2.2 Description of Procedures in the Existing Guidelines ....................................... 31 i FEMA COASTAL FLOOD HAZARD ANALYSIS AND MAPPING GUIDELINES FOCUSED STUDY REPORTS WAVE RUNUP AND OVERTOPPING 3.2.3 Application of Existing Guidelines to Topic—History and/or Implications for the NFIP ............................................................................................................. 31 3.2.4 Alternatives for Improvement ............................................................................ 31 3.2.5 Recommendations.............................................................................................. 39 3.2.6 Preliminary Time and Cost Estimate for Guideline Improvement Preparation. 39 3.2.7 Related Available and Important Topics............................................................ 39 4 IMPORTANT TOPICS ..............................................................................................................39 4.1 Topic 14: Review Available Methods and Develop Guidance for Wavecast Debris.. 39 4.1.1 Description of the Topic and Suggested Improvement...................................... 39 4.1.2 Description of Procedures in the Existing Guidelines ....................................... 41 4.1.3 Application of Existing Guidelines to Topic—History and/or Implications for the NFIP ............................................................................................................. 41 4.1.4 Alternatives for Improvement ............................................................................ 41 4.1.5 Recommendations.............................................................................................. 42 4.1.6 Preliminary Time and Cost Estimate for Guideline Improvement Preparation. 42 4.1.7 Related Available and Important Topics............................................................ 42 5 ADDITIONAL OBSERVATIONS................................................................................................42 5.1 Separating Wave Setup from Wave Runup .................................................................. 42 5.2 Implications of Using the Response Method................................................................ 43 5.3 Use of 2-D Models........................................................................................................ 43 6 SUMMARY ..............................................................................................................................44 7 REFERENCES..........................................................................................................................47 7.1 Printed References........................................................................................................ 47 7.2 Personal Communications............................................................................................ 51 Tables 1 Shore Types where Runup Estimates are Required for Flood Insurance Studies (Atlantic/Gulf Coasts and Great Lakes)......................................................................... 4 2 Interpretation of Mean Wave Overtopping Rates........................................................... 6 3 Summary of CEM Overtopping Guidance ................................................................... 33 4 Methods to Determine Wave-Overtopping Discharges for Various Structures ........... 35 5 Summary of Findings and Recommendations .............................................................. 44 6 Time Estimates for Runup and Overtopping Topics .................................................... 46 ii FEMA COASTAL FLOOD HAZARD ANALYSIS AND MAPPING GUIDELINES FOCUSED STUDY REPORTS WAVE RUNUP AND OVERTOPPING Figures 1 Wave runup sketch.......................................................................................................... 1 2 Overtopping of smooth, sloping structures..................................................................... 7 3 Simplified mapping of overtopped dune where runup exceeds crest by 3 feet or more. 8 4 Runup onto low bluff...................................................................................................... 8 5 Wave envelope and base flood elevations resulting from combination of wave heights and wave runup. ........................................................................................................... 10 6 Flow chart for WRUPTM. .............................................................................................. 18 7 Coastal Data Information Program, potential flood index tool..................................... 21 8 Oregon property erosion model. ................................................................................... 23 9 Illustration of the 2-D BW Model (wave penetration into a harbor) and the 1-D BW Model (wave transformation across a beach
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