slow shoaling 



MHW 



MWL- 



MLW 



100 150 



Distance seaward (m) 



r 



INSHORE 



NEARSHORE 



low 

 benm 



disslpative surf zone 

 with setup 



stonn 

 break 



rapid 

 shoaling 



150 200 



Distance seaward (ml) 



Figure 13. Beach classification system, showing (a) a reflective beach and 

 (b) a dissipative beach (after Wright, et al., 1979). 



Why do rip currents form? This question has been the subject of much 

 debate for 40 years. The summary of various mechanisms proposed to date 

 is taken from an excellent state-of-the-art report by Dalrymple (1978); 

 also. Miller (1977) provides excellent summary. This section concen- 

 trates on the physics, although Dalrymple goes much further into the 

 theory and equations supporting each model. Rip current spacing is a 

 product of the theory. 



There is no single theoretical model that can account for the presence 

 of rip currents. Rip current generation mechanisms are divided into two 

 main categories: (a) wave Interaction and (b) structural interaction. The 

 difference is that wave interaction mechanisms can occur on plain, infinite 



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