PART V: FLOOD STAGES FOR THE INTERIOR OF ROUGHANS POINT 



61. Once water levels, waves, and probabilities were determined for the 

 simulated events, three processes remained before stage-frequency curves for 

 the interior of Roughans Point could be constructed. These processes were the 

 physical modeling of both existing and proposed Roughans Point structures, 

 calculation of the overtopping rates, and routing of the resulting volumes 

 through the Roughans Point area. 



62. A two-dimensional physical model study was conducted to determine a 

 method to calculate the overtopping rates at Roughans Point. Figure 27 is a 

 map of Roughans Point showing the four northern reaches (A, B, C, and D) and 

 the two eastern reaches (E and F). Reach B was not included in the over- 

 topping analysis because its angle of orientation does not allow for direct 

 wave attack. Reach F was not included in the overtopping analysis since water 

 coming over this reach should flow toward the south away from Roughans 

 Point. The structure chosen for reach E will be continued for reach F, both 

 to provide protection for the integrity of the existing wall at reach F and to 

 provide a more suitable termination location for the structure. Model tests 

 were run for one proposed northern structure, the existing eastern structure, 

 and five alternative eastern structures. Analysis of the existing northern 

 structures (A, C, and D) was accomplished using overtopping data from a pre- 

 vious model study. Figures 28-31 contain drawings of the existing and origi- 

 nally proposed structure cross sections (NED 1983). Additional physical model 

 tests, varying the shape of the revetment and the height of the wall, were 

 conducted for the alternative structures for reach E (Figure 32). Only one 

 proposed northern structure was tested, and it was used at all the north reach 

 locations during simulations of the five different reach E alternatives. The 

 pertinent facts for the 10 structures are included in Table 7. For complete 

 details of the physical modeling see Ahrens and Heimbaugh (in preparation). 



63. The results of the physical modeling were coefficients ( Q Q and 

 C, in Table 6) for an overtopping rate equation (Equation 8). As indicated 

 below, Equation 8 determines overtopping rate per foot of structure length 

 with structure height, water level, wave height, and wave length as the 

 independent variables. 



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