PART VII: RESULTS AND CONCLUSIONS 



Roughans Point 



91. The stage-frequency curves for the interior flood levels in 

 Roughans Point are presented in Figures 36-40. For these curves it was not 

 possible to regress the total curve as was explained in Part VI. The physics 

 of the problem undergoes a sudden change at higher levels where the effect of 

 weir outflow limits the capacity of the interior of Roughans Point. Also the 

 extreme lower portion of the curves does not conform to the straight line 

 tendency of the middle portion. The lowest possible stage is 3.6 ft NGVD 

 corresponding to the lowest point inside Roughans Point. Consequently, the 

 stage-frequency curves remain at 3.6 ft until the onset of overtopping. 

 Therefore, the linear regression was limited to the middle segment of each 

 curve for the Roughans Point stage-frequency curves. Smoothing for both the 

 lower and higher segments of the curves was done by eye. 



92. As explained in paragraph 83, flood levels were calculated for six 

 different combinations of northern and eastern structures. The names of the 

 structure combinations plotted in Figures 36-40 refer to the names of the 

 eastern component. (For the "Existing" and "Original Proposal" structures 

 (NED 1983) refer to Figures 28-31, and for the other alternatives refer to 

 Figure 32.) Three tests lowering the height of the proposed north wall struc- 

 ture were conducted. Since it was determined that there was a negligible 

 difference between the curves with the originally proposed north wall height 

 (17 ft NGVD) and the curves from the highest of the three additional tests 

 (14 ft NGVD), curves resulting from the 17-ft height are not presented. 

 Curves for the six structure combinations are shown in Figures 36-38, with the 

 height of the northern structure in the three figures being 14, 13, and 12 ft, 

 respectively. Note that the 14-, 13-, and 12-ft north structure heights refer 

 only to the alternative structure combinations. For the "Existing" curve, 

 shown on these graphs for comparison purposes, the northern structure is set 

 at the existing height for each structure section. 



93. Using Figure 36, several features of the stage-frequency curves for 

 the interior flood levels at Roughans Point will be discussed. The greatest 

 differences among the alternatives occur at the lower return periods. Near 

 the 500-year return period all six curves tend to come together. As was 



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