TaskB 



Purposes 



16 



Purposes of Task B were to determine total overtopping for the design 

 storm event for the beach profiles surveyed in 1991 (after the beachfill 

 project) and to generate input data for a bore runup overtopping module to 

 be used with numerical models by CERC's Research Division. Using 

 wave data supplied by CERC's Research Division, Task B reproduced in 

 physical models the five beach profiles located along Revere Beach and 

 subjected them to the design storm event. Overtopping was measured for 

 each profile at each hour of the storm tested. 



Selection of test conditions 



The design storm event, or Standard Project Northeaster (SPN), was 

 based on a storm that occurred in November 1945. Wave conditions dur- 

 ing the storm were obtained by hindcasting; still-water levels during the 

 storm were obtained from the NOS Boston Harbor tide gauge. NED de- 

 fined the SPN as the wave conditions from the storm profile determined 

 by hindcasting for the November 1945 storm, but with an additional foot 

 added to the swl recorded by the NOS tide gauge throughout the storm. 

 The SPN was input by CERC's Research Division into the numerical models 

 listed under Task A to obtain storm conditions at Revere Beach. Figure 7 

 shows the storm profile for the SPN used as input to SBEACH. Condi- 

 tions to be tested in the physical model were selected from the storm pro- 

 file to include the worst conditions that occurred during the storm (hr 30) 

 plus conditions at two lower water levels during both tide cycles shown in 

 the storm profile (hr 27, 33, 40, and 45 for the lowest water level and hr 28, 

 32, and 43 for the higher water level). However, the static beachfill pro- 

 file reduced overtopping to such an extent that no overtopping occurred 

 during tests at the lowest water level; therefore, additional points from the 

 peaks of the tide cycles were selected for testing. As in Task A, linear in- 

 terpolation was used where feasible to adjust wave heights and periods to 

 maintain a constant swl for tests of the incoming and outgoing tides in 

 both tide cycles. Test conditions and the approximate hour of the storm 

 represented are listed in Table 4 after shoaling in SBEACH to the approxi- 

 mate location of the wave generator. As in the second set of tests in 

 Task A wave setup was allowed to occur naturally in the wave flume, and 

 the wave setup adjustment from SBEACH was not used. 



Determination of model profile 



Beach Profiles 1, 3, 4, and 5 were reproduced in the 18-in. flume at a 

 geometrically undistorted scale of 1:30. Examination of beach surveys 

 taken in 1991 indicated portions of the profiles could be represented by 

 the existing 1:30 concrete slope in the wave flume and the flat bottom of 



Chapter 3 Research Tasks A, B, and C 



