BREAKWATER 



APPROACHING WAVE 

 - CRESTS 



DIFFRACTED WAVES 

 INITIAL SHORELINE 



Figure 20. Shoreline response due to wave crests approaching parallel to 

 the shoreline (from Fulford (1985)) 



BREAKWATER 



TOMBOLO 

 CUSPATE SPIT 



APPROACHING WAVE 

 CRESTS 



DIFFRACTED WAVES 



LONGSHORE 

 TRANSPORT 



Figure 21 



Shoreline response due to wave crests approaching obliquely to 

 the shoreline (from Fulford (1985)) 



breakwater reaches the shore before the waves diffracted around the 

 structure's ends intersect (Dally and Pope 1986). 



Wave overtopping and transmission. Wave energy transmitted landward 

 of the breakwater due to overtopping and transmission through the structure 

 can also affect beach planform development and stability. If adequate wave 

 energy is allowed to pass through or over the structure, tombolo formation 

 can be prevented and/or salient formation can be inhibited. Tide level, wave 

 height and period, and structure slope and roughness all have effects on the 

 amount and form of energy transmitted due to overtopping (Shore Protection 

 Manual 1984). If overtopping occurs, the beach planform tends to flatten and 

 spread laterally in a uniform manner; however, waves overtopping the 

 structure have a shorter period than the incident wave and are highly 

 irregular. Wave energy passing through the structure is transmitted at the 

 same period as the incident waves, and is often more predictable and regular 

 than that produced by overtopping. In design, wave heights due to 

 overtopping are generally determined by the structure's crest elevation, and 

 wave transmission through a breakwater is determined by the structure's 

 permeability. A low-crested reef type breakwater is designed to allow 

 periodic overtopping of the structure by incident waves, thus preventing 



Chapter 2 Functional Design Guidance 



27 



