by rehabilitating the structure to crest heights of 26 and 28 ft can be read- 

 ily estimated. Although the model was not developed for this particular use, 

 data in Figure 2 logically indicate that the model is providing reasonable 

 trends. For small incident wave heights the transmitted wave height increases 

 at a decreasing rate, indicating that when transmission is entirely through 

 the structure the transmission coefficient decreases with increasing wave 

 steepness. The highest structure has the lowest transmitted wave height since 

 it has the largest cross-sectional area which attenuates most of the wave 

 energy passing through. As the incident wave height increases, a point is 



reached ( H =5.0 ft) where the lowest reef (most severely deteriorated) 

 mo 



experiences significant overtopping which causes the transmitted height for 

 this structure to increase, abruptly breaking away from the trend for the two 

 higher structures which have little or no overtopping at this wave height. At 

 an incident wave height of 7.0 ft, significant overtopping occurs on the reef 

 breakwaters with crest heights of 24 and 26 ft, and transmission trends have 

 gone well above the trend for the reef with a crest height of 28 ft which has 

 yet to experience significant overtopping. By comparing the transmission 

 trends for the various crest heights, it is easy to evaluate the potential 

 benefits of rehabilitating the crest of the structure. It should be empha- 

 sized that the data trends shown in Figure 2 as well as the trends to be shown 

 in Figures 3, 4, 5, and 6 are not observed data but are generated by a mathe- 

 matical model based on physical model tests (Ahrens 1987) . 



9. Figure 3 shows trends generated by the reef transmission model simi- 

 lar to those shown in Figure 2, except that the period of peak energy density 

 of the incident wave spectrum was changed from 8.0 to 12.0 sec to illustrate 

 the influence of wave period on transmission. As shown in Figure 3, the 

 longer period tends to transmit through the structure better, and when the 

 mode of transmission shifts at the higher incident wave heights to being 

 dominated by overtopping, the longer period waves transmit more energy by this 

 mode too. This occurrence leads to higher transmitted waves in Figure 3 for 



T = 12.0 sec compared to the transmitted waves in Figure 2 for T = 8.0 sec 



P P 



for all incident wave heights. 



10. The reef transmission model was used to generate another set of data 



similar to those in Figure 2 except that the median stone weight was changed 



from 5,000 to 8,000 lb. These results are shown in Figure 4. If Figure 4 is 



compared to Figure 2, it can be seen that when transmission is primarily 



