steven a. hughes. ph.d., p.e. - oas · • the surf-similarity parameter • runup no...

Coastal Engineering Practice CommitteeCEM Preview

Steven A. Hughes. Ph.D., P.E.Coastal and Hydraulics Laboratory

US Army Engineer Research and Development Center

David R. Basco. Ph.D., P.E.Coastal Engineering Center

Old Dominion University


Overview of Wave Runup and Overtopping

Overview of Wave Reflection and Transmission

Example Problems

CEM Chapter VI-5-2 (Author: Hans F. Burcharth)CEM Chapter VI-7 (Author: David R. Basco)

Based on:


Wave Runup: Vertical distance between SWL and maximum water elevation

Wave Rundown: Vertical distance between SWL and minimum water elevation

Wave runup determines structure crest elevation for minimal overtopping condition

Important:


Smooth Impermeable Slopes


Alternate FormulationSmooth Impermeable Slopes


Additional Factors

γγγγr - Influence of surface roughnessγγγγb - Influence of fronting bermγγγγh - Influence of shallow waterγγγγββββ - Influence of approaching wave angle


Impermeable Rock Slopes

Permeable Rock Slopes

Coefficients

• The Surf-Similarity Parameter• Runup

No Overtopping-ImpermeableSmoothRoughPartial-Safety FactorsStatistical Distribution

No Overtopping-Permeable• Overtopping

Average Discharge Rate• Summary CEM-vs-SPM

SUMMARY: WAVE RUNUPSUMMARY: WAVE RUNUP

1. Significant Wave 1. Significant Wave RunupRunup, , RRusus

•• Both SPM (1984) and CEM (2000) give Both SPM (1984) and CEM (2000) give similar resultssimilar results

•• CEM (2000) methods easy for EXCELCEM (2000) methods easy for EXCEL

2. Prevent overtopping 2. Prevent overtopping -- Statistical distributionsStatistical distributions•• RuRu2%2% based on actual, largebased on actual, large--scale tests, scale tests,

irregular wavesirregular waves•• Estimates of Estimates of RuiRui% based on % based on Rayleigh Rayleigh

distribution are incorrectdistribution are incorrect

SUMMARY: WAVE RUNUPSUMMARY: WAVE RUNUP

3. Permeable Breakwaters3. Permeable Breakwaters•• Little data in SPM (1984)Little data in SPM (1984)•• Core permeability significantly influences Core permeability significantly influences

resultsresults•• Methods now available in CEM (2000)Methods now available in CEM (2000)

Use CEM (2000) methods to estimate wave Use CEM (2000) methods to estimate wave runuprunup


• Occurs where the highest runup levels exceed the freeboard• Unevenly distributed in space and time• Usually expressed as time-averaged overtopping discharge• Discharge from a single wave can be 100 times average

Definition of freeboard

Wave Overtopping...

Critical AverageOvertoppingDischarges


Generally expressed in the form...

Typical CEM Table(one of six)

SUMMARY: WAVE OVERTOPPINGSUMMARY: WAVE OVERTOPPING

1. Average wave overtopping rate1. Average wave overtopping rate•• Both SPM (1984) and CEM (2000) give Both SPM (1984) and CEM (2000) give

similar resultssimilar results•• CEM (2000) methods easy for EXCELCEM (2000) methods easy for EXCEL

2. Critical values for traffic and structural safety2. Critical values for traffic and structural safety•• SPM (1984) gives no informationSPM (1984) gives no information•• CEM (2000) gives critical values to justify CEM (2000) gives critical values to justify

raising crest elevationraising crest elevation

SUMMARY: WAVE OVERTOPPINGSUMMARY: WAVE OVERTOPPING

3. Volume estimates for individual waves3. Volume estimates for individual waves•• CEM (2000) gives methodsCEM (2000) gives methods

Use CEM (2000) methods to estimate wave Use CEM (2000) methods to estimate wave overtoppingovertopping




Example Problems

Based on: CEM Chapter VI-5-2 (Author: Hans F. Burcharth)CEM Chapter VI-7 (Author: David R. Basco)


Bulk Reflection Coefficient


Structure a bSeelig Equation

With


Six other cases are given


Transmission Coefficient


Van der Meer andd’Angremond (1991)

• Conventional • Low-crested• Reef breakwaters




Example Problems

Based on: CEM Chapter VI-5-2 (Author: Hans F. Burcharth)CEM Chapter VI-7 (Author: David R. Basco)

Figure V-3-6

Virginia Beach seawall/boardwalk (a) artist’s perspective (b) aerial photo, 1997 (courtesy of Virginia Beach, VA)

steven a. hughes. ph.d., p.e. - oas · • the surf-similarity parameter • runup no...

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