where L^ = gT^llit and tan 6 is either the structure slope or the beach slope, depending 

 on where the wave breaks. The wave height H is usually either H^ or H^, and the 

 period is the mean period for armor stability (Van der Meer 1988). The Iribarren 

 parameter can be used to characterize the type of wave breaking with ^ < 0.3 

 corresponding to spilling waves, 0.3 ^ ^ £ 2 to plunging waves, 2 :£ ^ ^ 3 to collapsing 

 waves, and ^ ^ 3 to surging waves. Van der Meer (1988) and others have used the 

 structure slope in Equation 4.9. This is because they were primarily testing with 

 nonbreaking waves on the beach. But for the experiment described herein, the wave 

 heights were depth limited. So the beach slope was the critical parameter dictating the 

 type of wave breaking near the structure and was therefore used to compute ^. It is clear 

 from Tables 4.3 and 4.4 that, for these tests, the most severe waves were primarily 

 plunging. This corresponds to the design condition for most United States shoreline 

 applications. The relative depths show that the wave condition selected is near the 

 worst case for stability according to Figure 3.3. 



The stability numbers shown in Table 4.4 were in the range A^^ = 1.6-2.5. 

 This is well within the range o{N^= 1-4 for conventional breakwaters suggested by Van 

 der Meer (1988). On the other hand, stability coefficients in Table 4.4 based on H^o are 

 in the range 3.4-13.2 in comparison to K^ = 2.0 recommended in the SPM for breaking 

 waves on rough angular stone armor placed on a trunk. This indicates that the 

 breakwaters in this experiment will incur some damage. 



73 



