PART V: CONCLUSIONS 



43. Based on the 2-D physical model test results reported herein, it 

 was concluded that: 



a. Regarding wave overtopping and berm stability tests for the 

 storm conditions to which the structures were subjected: 



(1) The berm design characterized by stone weights of 250 lb 

 was not acceptable in terms of stability of the riprap 

 structure. 



(2) The berm design using 1,000-lb stones was acceptable. 



(3) Visual assessment indicated that the riprap toe played an 

 important role in reducing overtopping at swl's of +7.0 ft 

 or less and a lesser role at the +8.0- and +9.5-ft swl's. 



(4) Overtopping rates measured with the Phase II seawall geom- 

 etry in place were less than corresponding rates measured 

 with the Phase I design. 



(5) Overtopping rates observed with a +I.O-ft beach elevation 

 can be expected to decrease by as much as 78 percent for a 

 hurricane event at a +8.0-ft swl with a beach elevation of 

 +3.4 ft. 



(6) Much of the data scatter in the overtopping results seems 

 to be caused by the occurrence of seiche in the wave 

 flume. 



b. Regarding wave pressure testing: 



(1) Shock pressures as great as 117 psi were recorded; how- 

 ever, durations of pressures greater than 15 psi were 

 typically less than 0.020 sec. 



(2) At swl's of +8.0 and +9.5 ft, maximum pressures consis- 

 tently occurred at the vertex of the wall curvature. 

 Highest pressures were also common on the face of the top- 

 most step at these swl's. 



(3) At the +7.0-ft swl, maximum pressures occurred on the 

 faces of the lowest three steps. 



(4) Secondary pressure magnitudes were relatively consistent 

 at approximately 5 to 10 psi. Durations of significant 

 secondary pressures ranged from 2.0 to 3.0 sec. 



(5) No significant durations of negative pressures were re- 

 corded. Design calculations for uplift pressures on the 

 Phase II seawall may be performed neglecting any contribu- 

 tion due to wave runup or recession. 



44. Relative to wave overtopping, results of this model study indicate 

 that the Phase II seawall geometry is a more effective design of the two 

 alternatives tested. At the +8.0-ft swl, overtopping rates measured during 



37 



