20. ABSTRACT (Continued) 



Northeaster all structure combinations tested would be ineffective at pro- 

 tecting the interior of Roughans Point. Tests were conducted to determine a 

 structure height for the north wall. These tests indicated that significant 

 overtopping did not begin until the north wall structure was lowered below 

 13 ft National Geodetic Vertical Datum (NGVD). Since the existing height of 

 the north wall is above this level at several sections, it is recommended that 

 the revetment height be set at 13 ft NGVD with the wall height set so that 

 there is a transition between the existing wall heights. 



For areas where stage-frequency curves are presented for the still-water 

 level resulting from the combination of storm surge and astronomical tide, 

 only the storm surge and probability models were necessary. These areas in- 

 clude both open coast and estuarine locations. For areas flooded by the 

 still-water level, results of the modeling indicated that the whole study area 

 floods to approximately the same level. Flood levels are efficiently conveyed 

 through the inlet and throughout the flood plain of the Saugus-Pines River 

 system. Inside the inlet, there is a small gradient in the still-water level, 

 rising from north to south, which results from local setup caused by north to 

 northeast wind directions which predominate during storm conditions. This 

 local wind setup results in flood levels inside the inlet which differ by one- 

 half to three-fourths of a foot during the more severe storm events. Outside 

 the river system in Broad Sound a smaller north-south gradient exists with 

 differences of only a few tenths of a foot resulting. Data collected by the 

 US Army Engineer Division, New England, after completion of the modeling 

 indicated that losses do occur as flood levels propagate upstream of the Fox 

 Hill Drawbridge on the Saugus River and upstream of the Highway embankment on 

 the Pines River. Stage-frequency curves for these areas were adjusted to 

 accommodate these additional data. The curves were lowered 0.3 and 0.5 ft at 

 the lower return periods for upstream Saugus River and Pines River locations, 

 respectively. Reductions were reduced for higher return periods because 

 higher flood levels would provide greater access of floodwaters to these 

 areas. 



The setup and operation of all models, except the physical model, are de- 

 scribed. The method of constructing stage-frequency curves is explained, and 

 estimates of the error involved in each of the processes are discussed. The 

 final products are curves which relate flood stage to frequency of occurrence 

 for several possible structures at Roughans Point as well as for several 

 coastal and river areas. 



