The Hudson equation was defined for regular waves but has been extended 

 to irregular waves using irregular wave physical model experiments. The SPM suggests 

 //,/,o, the average height of the highest 1/10 waves, to replace the regular wave height in 

 Equations 2.1 and 3.5, but the justification is unclear. Researchers attempted to relate 

 regular and irregular wave effects on stability in the 1970s with no definite conclusions 

 (e.g., Jensen (1984)). Recently, Vidal et al. (1991); Vidal et al. (1995); and Jensen et al. 

 (1996) emphasized the need for characterization of the large waves in a random wave 

 train. Vidal et al. (1995) noted that representation of the irregular time series by //,oo, 

 the average height of the highest 100 waves, provided a comparative level of damage to 

 that produced by regular waves; but the equivalent statistic of the form Hy„ will depend 

 on the number of waves. Medina and McDougal (1988) introduced an interesting, albeit 

 not rigorous, method for interpreting Jackson's (1968) regular wave damage results 

 using a Rayleigh wave height distribution. Their method incorporated storm duration 

 into the equation. In sununary, the regular wave stability and damage formulations 

 given above are conservative for design; but a universal analytical technique for 

 extending these relations using irregular waves and resulting damage development has 

 not been completed. 



Thompson and Shuttler (1976) performed both long-term deterioration and 

 shorter single-storm damage tests using a riprap-armored embankment with an 

 impermeable core. All of their tests were restricted to nonbreaking waves in front of the 

 embankment, mostly deep water. The average run length was 5,000 waves, based on 



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