height to the wall behind it, as is seen in both the "Wide Berm + 1-ft Cap" 

 and the "Wide Berm + 2-ft Cap" alternatives. Studying the overtopping rate 

 equation (Equation 8) shows that the overtopping relationships developed from 

 the physical model are very sensitive to freeboard and, therefore, to struc- 

 ture height. 



97. Recommending a height for the north wall is difficult. None of the 

 three heights were actually modeled by the physical model. The final struc- 

 ture selected must, of course, result from a detailed economic analysis. The 

 technique of using the 17-ft north wall physical model results to predict the 

 results for lower revetment heights by lowering freeboard was the best avail- 

 able but must lower confidence in the analysis. The choice seems to be be- 

 tween the 13- and 14-ft heights. The 12-ft height allows significantly great- 

 er overtopping to occur. Figures 39 and 40 show the effect of north wall 

 height on the "Wide Berm" and the "Wide Berm + 1-ft Cap", respectively. Since 

 the height of the existing wall sections at A and C (15.3 and 13.7 ft NGVD) is 

 higher than that of the 13-ft trial, the best choice would be a revetment at a 

 13-ft height with the wall keeping its existing height at A and C, with the 

 height at B being a transition between A and C, and the height at D matching 

 that at C. 



Still-Water Locations 



98. Stage-frequency curves for 14 locations within the Saugus-Pines 

 River system and the coastal areas bordering Broad Sound are presented in 

 Figures 41-54. Figure 23 shows the location of these 14 numerical gages. 

 Just prior to the completion of the study, additional data were collected by 

 NED during the highest predicted tides of September, October, November, and 

 December 1985 for several locations in the extreme upriver portions of the 

 modeling area (Figure 55). Because of increased interest in flood protection 

 for these areas, it was hoped that the additional data would allow adjustment 

 of the modeling results upstream of where calibration data were previously 

 available. Data were collected also at the Fox Hill Drawbridge calibration 

 gage location, and data for the Boston tide gage were obtained from NOS. 

 These data are summarized in Table 10. 



99. Based on the information shown in Table 9, adjustments were made to 

 those numerical gage locations west of the abandoned highway embankment and 



72 



