guidance available in the Shore Protection Manual (SPM) (1984) provides the 

 basic tools for planning and designing breakwaters. This paper is intended to 

 supplement that guidance by providing a practical perspective to the wide 

 variety of environmental data now available to coastal engineers for rubble- 

 mound breakwater design. 



Scope 



2. A brief review is presented of past and present criteria development 

 procedures, design techniques, and related practical considerations, followed 

 by a more detailed discussion of breakwater damage prediction and estimation 

 of wave transmission characteristics. A systematic procedure is proposed to 

 formulate alternative cross-section designs, evaluate their structural and 

 functional effectiveness, and determine detailed dimensions which realize max- 

 imum net incremental benefits. 



Definition and Purposes of Rubble-Mound Breakwaters 



3. Breakwaters and, to some degree, jetties and groins are designed as 

 barriers to sea waves, providing calmer water in their lees. Wave barriers 

 can be constructed in many different ways, including vertical-sided concrete 

 caissons, sheet-pile walls, wooden crib structures, and floating bodies. The 

 oldest and most common type of wave barrier is the rubble-mound breakwater be- 

 cause of its typical economy and constructibility in harsh coastal conditions. 

 The long history of rubble-mound breakwaters has proven them quite reliable in 

 a wide range of environments (Bruun 1985). A rubble-mound breakwater consists 

 of sloped layers of stone or concrete shapes that are sized to withstand wave 

 attack, excess settlement or loss of fill material, and to prevent scour, as 

 shown in the typical cross section in Figure 2. Their inherent flexibility 



DESIGN WAVE 

 HEIGHT, H 



CREST 

 ELEVATION 



:^ ^ 



CREST WIDTH 



DE SIGN SWL 



S WL (MINIMU M) 

 (SECONDARY ARMOR) 



Figure 2. A typical rubble-mound breakwater 

 cross section 



