The site is exposed to Atlantic Ocean storms, with predominant swell from 

 300 deg north in the winter months. The sponsor-predicted 50-year return period 

 wave height ranged from 6.7 to 7.5 m. A secondary summer storm swell is inci- 

 dent from approximately 230 deg north. 



The existing main breakwater is shown in Figures 3 and 4, with the layout 

 view in Figure 4 dividing the breakwater into seven profiles. The porous break- 

 water consists of a traditional rubble mound fronting a recurved seawall. The 

 crest elevation of the seawall is +8.15 m CD (CD refers to the lowest theoretical 

 chart datum) while the crest elevation of the 6.25-tonne-tetrapod armor layer is 

 approximately +7 m CD. The head of the breakwater was virtually destroyed by 

 storms over 25 years and its remnants are completely submerged. The remaining 

 tetrapod-armored trunk section extends south for approximately 180 m from 

 Profile 1 (Figure 4). The existing tetrapod section extends down to 

 approximately m CD. 



The depth along the toe varies from near 2 m along the trunk to 9 m on the 

 head, so the significant wave in the design spectrum is depth limited. The water 

 level can vary up to 2 m due to a combination of both tide and storm surge. The 

 seaward bottom slope is relatively steep, averaging between IV on 12H to 

 IV on 15H. The foundation at the site consists of layers of sand over bedrock or 

 old breakwater remnants with sporadic rock outcroppings. Net littoral drift is to 

 the south. 



Much of the trunk section shows considerable damage to the existing tetrapod 

 armoring. The main armor of tetrapods was under-designed for the 50-year 

 return period, 7-m significant wave height at the head. Tetrapods along the trunk 

 section north of Profile 4 have remained relatively stable. 



Purpose 



A breakwater rehabilitation has been proposed for Vale de Cavaleiros. The 

 rehabilitation would include extending the breakwater length, placing all sal- 

 vageable tetrapods in Profiles 1 through 4, and placing Core-Loc armor units on 

 the remainder of the structure. At the request of Joint Venture Rhein Ruhr 

 Ingenieur-Gesellschaft mbH and BCEOM Societe Francaise d'Ingenierie (TV 

 RRI-BCEOM), a breakwater stability model investigation was initiated by the 

 U.S. Army Engineer Waterways Experiment Station's Coastal Engineering 

 Research Center. The study goal was to evaluate the stability of the Core-Loc 

 armor layer for the proposed rehabilitation of the breakwater. 



This report describes the design and facilities used (Chapter 2), and results of 

 the three-dimensional stability study (Chapter 3). The study is summarized in 

 Chapter 4. Appendix A contains photographs of the three-dimensional model 

 and Appendix B includes symbol notation used in the report. 



Chapter 1 Introduction 



