Testing segmented breakwater plans at the -4.6-m depth contour (Figure 44) 

 showed that shorter segments with shorter gaps produced weaker rip currents 

 and retained most of the tracer material, but a large volume of stone was 

 required for construction. Submerged structures at the -3.0-m depth revealed 

 that breaking waves piled water between the breakwater and shoreline, and the 

 seaward return of the water created strong rip currents and the loss of tracer 

 material to deep water. Test results with segmented breakwaters located at the 

 -1.5-m contour with gaps indicated there was too much wave transmission in 

 the structure lee. Low sills were placed in the gaps (Figure 45) and were 

 successful in retaining all but small quantities of tracer, and thus the low sills 

 between breakwater segments appeared to reduce the total wave transmission 

 and caused the least impact on longshore transport. 



Figure 44. Typical wave and current patterns and current magnitudes for segmented 



detached breakwaters at the -4.6-m contour in the Imperial Beach model (Curren 

 and Chatham 1977) 



Chapter 3 Tools for Prediction of Morphologic Response 



75 



