Overview of Project Technique 



4. The establishment of frequency curves required the conjunctive use 

 of several modeling components. At Roughans Point the combined use of prob- 

 ability, numerical storm surge, numerical wave, physical, and flood routing 

 models was required to produce the stage-frequency curves. Whereas, for the 

 still-water locations (Saugus-Pines River and Revere Beach-Lynn Harbor areas) 

 only the probability and numerical storm surge models were required. The 

 following is a brief description of each model. 



5. The probability model was designed to complete four tasks: select 

 events for simulation by the other models, assign probabilities to these 

 events, create stage-frequency curves, and determine a measure of confidence 

 in the final results. The numerical storm surge model simulated the storm 

 plus tide events producing a time-history of still-water levels at specific 

 locations throughout the study area. A numerical, spectral wave model simu- 

 lated the wave field which accompanied each of the events simulated by the 

 storm surge model. Also, a monochromatic wave model estimated the locally 

 generated waves which were not considered in the spectral model. The wave 

 parameters of height, period, and direction were calculated at selected sites 

 throughout the study area. The physical model determined coefficients for an 

 overtopping rate equation by testing multiple combinations of water level and 

 spectral wave characteristics for several existing and proposed structures at 

 Roughans Point. The physical modeling is not fully described in this report. 

 (For complete details of the physical modeling see Ahrens and Heimbaugh (in 

 preparation). The flood routing model calculated the maximum stage in the 

 interior of Roughans Point caused by each event. Maximum stage was determined 

 after outflows from drainage, pumping, seepage, and weir flow over low lying 

 boundaries were considered. 



6. Figure 3 is a flow chart which depicts the conjunctive use of the 

 above models for the establishment of stage-frequency curves. Basically, the 

 probability model selected and assigned probability to the surge-tide-wave 

 events simulated. Then, the surge model simulated the still-water level. At 

 this point stage-frequency curves were generated for the still-water loca- 

 tions. To develop the flood levels caused by wave overtopping at Roughans 

 Point, the wave, physical, and flood routing models were necessary. The wave 

 model simulated the parameters, height, period, and direction. The output of 



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