2. Offshore Breakwaters with Gaps. 



Overtopping of breakwaters causes a buildup of water in the zone landward 

 of the structure. If there are gaps between the breakwaters and the breakwaters 

 are not connected to shore, the buildup of water landward of the breakwaters 

 causes flow through the openings (Fig. 4). One method of estimating the exit 

 flow through breakwater gaps or inlets is to use a combined continuity-energy 

 equation for discharge. 



Q = VA C = C d ^2gh b A c 



(5) 



where C^ is a discharge coefficient, A c is cross-sectional flow area at 

 the water level of interest, and V is the mean velocity of water flowing 

 through the gaps. Many factors may influence the magnitude of C^ but, as 

 a first estimate, C^ = 0.8 is recommended for gaps. The discharge coefficient 



for spaces between breakwaters and the shoreline, 

 value of C<j e = 1.0. 



Cde 



has a recommended 



Breakwater 



h t> = Difference 

 in Mean Water 

 Levels 



I 



Overtopping 



N=3 



End Flow 

 Shoreline 



Figure 4. An offshore breakwater system. 



