Modeling Local Bathymetry 



7. Local prototype bathymetry was represented by a lV-on-35H slope, 

 starting at the toe of the existing breakwater and extending seaward for a 

 simulated prototype distance of 425 ft (7.4-ft model), followed by slopes of 

 IV on 85H and IV on 20H with simulated prototype distances of 805 ft (14-ft 

 model) and 725 ft (12.6-ft model), respectively (Figure 2). Shoreward of the 

 existing breakwater toe the bottom was assumed to be flat, with a simulated 

 prototype elevation of -29 ft mean lower low water (mllw). 



Selection of Test Conditions 



8. Surge levels from the prototype data indicated that the extreme 

 range of water levels that could be expected at the breakwater during its de- 

 sign life was -1 to +10 ft mllw. Four water levels were selected for testing. 

 They included simulated prototype surges of -1, +4, +7, and +10 ft mllw. 



9. For a given wave period and water depth, the most detrimental 

 breaking wave (i.e., the most damaging wave) was determined by increasing the 

 stroke adjustment on the wave generator in small increments and observing 

 which wave produced the most severe breaking wave condition on the structure. 

 Wave heights of lower amplitude did not form the critical breaking wave, and 

 wave heights of larger amplitude would break seaward of the test section and 

 dissipate their energy so that they were less damaging than the critically 

 tuned wave. 



10. Initially, test sections were subjected to an abbreviated hydro- 

 graph (Table 1 and Plate 1). Only those plans which showed an acceptable 

 stability response for the abbreviated hydrograph were tested with the full- 

 length hydrographs. Two typical storm-surge hydrographs, representative of 

 conditions along the Northern California Coast, were furnished by the sponsor, 

 Test conditions for these hydrographs are listed in Tables 2 and 3. Plates 2 

 and 3 graphically depict surge level as a function of time. 



11. The breakwater is generally exposed to waves clockwise from south 

 to west. From the refraction, diffraction, and shoaling report (Hales 1985), 

 the most severe depth-limited breaking waves that can reach the structure 

 occur from the southern to the southwestern direction and intersect the main 

 stem of the breakwater at approximately 67.5 and 90 deg, respectively. 



