not described in detail in any public references. As such, it will be described herein. In 

 this volume method, the active armor layer was defined as extending from the middle of 

 the breakwater crest to one zero-damage wave height below the still water level. The 

 damage was determined through profiles using a sounding rod with a circular foot of 

 diameter equal to 0.56Z)„so, where D„^q = (W^^y^^'^ is the nominal diameter of the 

 median stone weight, W^ and Ya is the specific weight of armor stone. The sounding 

 disc size was determined so that the before-testing armor layer thickness, determined 

 using the measured profile, coincided with the theoretical value. The soundings were 

 generally obtained on a horizontal grid spaced evenly at 1.5D„5o. A number of profiles 

 along the breakwater length were averaged to determine an average profile. The 

 average damaged profile was subtracted from the undamaged average profile to get an 

 average eroded area over the active region. The eroded cross-sectional area is defined in 

 Figure 3.1. This eroded area was divided by the total area of armor in the undamaged 

 average profile to get a percent damage D%. Hudson's (1959) zero-damage criteria 

 corresponded to D% < 1 percent. The zero-damage criteria given in the Shore 

 Protection Manual (SPM 1984) corresponds to D% < 5 percent by the eroded volume 

 method or 2 percent by count. The justification for the less restrictive zero-damage 

 criteria is not clear but evolved over many years. 



The primary weakness of the WES eroded volume method is that, because 

 the damage is only computed over the active region, the damage value will depend on 



35 



