ments of wave set-up were obtained for one station plus one independent 

 measurement for each of three other stations. This gave wave set-up 

 values at four points relative to the shoreline and also some indica- 

 tions from the fixed gage station data (3 values) of the reproducibility 

 of the model tests. The variability of a wave set-up value for an 

 initial test run and for the same run repeated was generally of the 

 order of 0.2 foot or less. The fixed gage stations for the 1.75-foot 

 and the 8-foot water levels were 200 feet seaward and 375 feet land- 

 ward respectively of the MHW line. These stations were the farthest 

 landward of the. four stations for each water level and therefore may 

 be expected to reflect the maximum wave set-up for a given test con- 

 dition. 



Test C^eration 



The steps taken prior to an actual test run were: adjustment of 

 water level in the model tank for proper test depth, setting speed 

 control on wave generator for the correct wave period, proper placement 

 of the wave set-up gages, and adjustment of eccentric setting for the 

 correct wave height. The last of these steps, eccentric setting for 

 the correct wave height, required that one or more trial runs be made 

 during which time the wave height was measured and checked for agree- 

 ment with the desired wave height. 



As the first waves reached the beach in the test runs, the still 

 water level increased sharply, and then oscillated about a mean level 

 as the initial increase was reflected from the onshore area and created 

 a surge in the tank. The magnitude of this oscillation decreased with 

 time until an essentially constant still water level was obtained (see 

 Figure 4). Therefore, during the actual test run, the equipment was 

 operated for a period of 5 to 10 minutes to insure that the wave set-up 

 had become stabilized to the extent that an essentially constant set-up 

 stage was observed. In general, the set-up for larger wave heights and 

 longer wave periods required more running time to become stabilized 

 than did the set-up for the smaller wave heights and shorter wave periods. 



Analysis of Results and Conclusions 



Analysis of the test data indicates that there is a rise in the 

 average water level due to the wave conditions tested; this rise is 

 called the wave set-up. The amount of the wave set-up appears to 

 depend on several factors among which are distance from the shoreline 

 (depth), wave height, and wave period. The relations between the wave 

 set-up and the several factors mentioned above are shown in Figure 5. 



There is reason to believe that the surge elevation measurements at 

 Narragansett Pier may have occurred in a low-lying area formed in back 

 (landward) of the MHW line during hurricane wave conditions. Because 

 of this, a pool area landward of the berm crest (Figure 3) was included 



15 



