3 Research Tasks A, B, and C 



Task A 



Purpose 



The purpose of Task A was to validate the numerical and physical 

 models by reproducing the effects of a known storm event. The storm 

 selected for the test occurred in February, 1978; surveys of high-water 

 marks in ponding areas provided an estimate of the total overtopping over 

 the reach represented by Profile 2, which is located fronting the proposed 

 park dike. Using wave data supplied by CERC's Research Division, 

 Task A simulated the 1978 storm in the physical model to determine if 

 overtopping measured in the 2-D model corresponded to the estimated 

 prototype overtopping volume. 



Selection of test conditions 



The National Ocean Survey (NOS) Boston Harbor tide gauge provided 

 data on local water levels. Wave conditions were determined by CERC's 

 Research Division with the following numerical models: deepwater wave 

 hindcast information was brought shoreward using numerical model 

 SHALWV, diffracted and refracted into Broad Sound by numerical model 

 REF/DIF, and transformed shoreward along each of the surveyed profiles 

 using numerical model SBEACH. SHALWV uses spectral wave informa- 

 tion; REF/DIF and SBEACH use monochromatic waves. The height of 

 the average of the one-third highest waves (significant wave height H^) 

 and the period of peak energy density (r„) calculated from the wave en- 

 ergy spectrum determined by SHALWV were chosen to characterize the 

 monochromatic wave transformation in REF/DIF and SBEACH. 



Still-water level (swl), wave height, and wave period were determined 

 for each hour during the selected storm to define the storm profile, and 

 test conditions for the physical model study were selected from the storm 

 profile. Figure 5 shows the storm profile used as input to SBEACH. For 

 the physical model study, water level at the peak of the second tide cycle 



Chapter 3 Research Tasks A, B, and C 



