push water up the Pines River away from the inlet, pumping more water into the 

 river system. Curves for locations upstream on the Pines River would be fur- 

 ther increased by the effect of the wind setting up the water over the shallow 

 marsh areas. In general there was a small north to south gradient in flood 

 levels with the more southern areas higher by one-half to three-fourths of a 

 foot during the more severe events. For the Broad Sound locations a smaller 

 variation of a few tenths of a foot with the higher levels at the more south- 

 ern locations also is explained by the direction of the winds. 



101. Stage-frequency curves are not presented for the marsh areas west 

 of the highway embankment. Modeling the routing of the floodwaters in these 

 areas is beyond the scope of this study. For lower return periods observa- 

 tions indicate there is a head loss as the waters go north from the Pines 

 River channel across the Saugus Marsh. In these areas, at lower return 

 periods, flow is contained in drainage ditches which are too small to model 

 with the present grid resolution. Also, other subgrid effects such as loca- 

 lized areas of high ground which could thwart the movement of floodwaters are 

 important but were not considered. 



102. It is important to emphasize that the effects of ice and snow were 

 not taken into account by the storm surge modeling. It is possible and 

 perhaps even likely that severe northeasters would be accompanied by heavy 

 accumulations of snow and ice formation in the river systems. Snow banks 

 formed from the clearing of roadways could act to divert floodwaters and 

 provide some measure of protection to some areas. Ice could restrict bridge 

 and channel openings and, therefore, reduce the amount of water entering back 

 areas. Ice cover of open water would likely reduce the wind setup of the 

 marsh areas. Although the above mentioned effects indicated the effect of ice 

 and snow would be to reduce flood levels, scenarios are possible where the 

 opposite would be true. For example, ice could divert the flood into areas 

 which would not have been affected without the diversion. 



Estimating Error in the Frequency Curves 



103- The final products of this study are curves which depict stage 

 versus return period for flood levels at many locations throughout the study 

 area. At any one return period, say 100 years, the curve is merely an esti- 

 mate of the true flood level. Moreover, this estimate is only a point 



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