events were simulated for the existing one and five alternative structure com- 

 binations. Inputs to the model were the time-histories of overtopping rates 

 for each of four Roughans Point reaches (A, C, D, and E). Six different com- 

 binations of the northern and eastern reach structures were modeled. Since 

 the north wall has only two structure classes, "Existing" and "Original Pro- 

 posal," a combination of northern and eastern structures was given the name 

 of the eastern structure. The "Existing" combination is self-explanatory. 

 The "Original Proposal" combination is made up of the northern and eastern 

 structures proposed before the beginning of modeling (see Figures 28-31 and 

 NED 1983). The other four alternatives, "Wide Berm," "Two Berms," "Wide Berm 

 + 1-ft Cap," and "Wide Berm + 2-ft Cap," combined the eastern structure of the 

 same name (see Figure 32) with the northern "Original Proposal" structure. 

 There were two output files. One file was a time-history of flood stages for 

 each event and structure simulated. The second file contained the maximum 

 stage during each event for each combination of structures simulated. This 

 second file was used to compute the stage-frequency curves. 



North Wall Tests 



84. During the course of simulating overtopping and flood routing, 

 there was no contribution to overtopping volumes from the "Original Proposal" 

 northern structure. Tests were conducted to determine the effect of lowering 

 the height of the protection along the whole north side of Roughans Point. 

 Since no additional physical model tests were to be run, a method had to be 

 devised to use physical model data from the proposed northern structure 

 (17 ft). Reconsideration of the overtopping rate equation (Equation 8), re- 

 veals that changing the height of the northern structure would only change one 

 term in that equation, namely F , the freeboard. Since the water level would 

 not be changed, the characteristics of the waves attacking the structure would 

 not be changed. Therefore, even though lower heights were not tested, esti- 

 mates of the overtopping for lowered structure heights could be made by re- 

 ducing the freeboard in Equation 8. Using the February 1978 historic event 

 for the initial tests, the northern structure was lowered in 1-ft increments. 

 For this event, overtopping did not start until the structure was lowered to 

 14 ft NGVD, and large volumes of overtopping did not commence until a struc- 

 ture height of 12 ft NGVD was tested. Using these results, the full ensemble 



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