PART III: PRESENTATION OF RESULTS 



Development of Overtopping Parameters 



12. One of the most important findings of this study was the develop- 

 ment of a dimensionless relative freeboard parameter F 1 which consolidated 

 all of the data for one structure configuration into a single trend. The 

 term, F 1 is defined 



(1) 



where F is the freeboard, i.e., the difference between the crest height of 

 the seawall and the local SWL, and L is the Airy wave length calculated 

 using the water depth at Gage 7 and the nominal T Q . Equation 1 can be 

 thought of as the ratio of the freeboard and the severity of the local wave 

 action. The term F 1 combines a large amount of information into one param- 

 eter which contains the seawall crest elevation, the local water depth or 

 water level, the zero-moment wave height, and the period of peak energy 

 density of the spectrum through the use of L . This parameter, F' , seems 

 to consolidate the data into a single trend better than other variables, in- 

 cluding the parameter F/H^ suggested by the work of Goda (1969) and Seelig 

 (1980) or the dimensionless freeboard parameter F/(T z gH g ) used by Owen 

 (1982), where T z is the zero-crossing wave period, H is the significant 

 wave height, and g is the acceleration of gravity. Using L Q in the F' 

 parameter seems to be a very effective way to account for wave period effects 

 which are conspicuous when observing the laboratory tests. After a short time 

 of model observation, it was obvious (other factors being equal) that the 

 larger the T of the spectra the greater the overtopping. 



13. Following the rationale given above, the overtopping rate Q is 

 plotted versus F' (Plates 1-10) for all of the seawall/revetment configu- 

 rations given in Table 1 . The overtopping rate Q is defined as the volume 

 of water overtopping the seawall per unit length of seawall per unit time. 

 For this study, Q is given in units of cubic feet per foot per second. Also 

 shown in Plates 1 through 10 is a regression curve which has been fit to the 



15 



