were changed to form subruns during this lengthy run, at least 3 minutes 

 were allowed before data were collected to permit the wave and runup 

 conditions to "stabilize." The subruns are designated as runs 1 to 8 in 

 Table 3. 



Since the runup gage and board occupied the entire width of the tank, 

 there was no room for wave absorber material and wave filters were not 

 used. For the long-period monochromatic waves used to simulate the condi- 

 tions of Saville (1956) and Savage (1958), a standing wave pattern was 

 noted in the tank during a wave burst. However, the results of this study 

 are largely confined to wave periods of about 2 seconds or less where 

 there was little visual evidence of reflection. The magnitude of the 

 reflection was not measured. 



The seven unique wave conditions and one replicate of increasing 

 complexity (runs 1 to 8, Table 3) are parameterized by giving the root 

 mean square water surface displacement, ^> rms , the significant wave height, 

 H s , the mean zero up-crossing period, T z> the spectral width parameter, e, 

 and the ratio of the highest crest, D(max) to D rms . The length of record 

 used to compute the various parameters is also shown in Table 3. D^ms was 

 computed from the wave record digitized at a rate of five times per second. 

 H s is the average of the highest one-third of the waves. T 3 , calculated 

 by Draper's (1966) method, is the length of record in seconds divided by 

 the number of zero up-crossings . The spectral width parameter, was calcu- 

 lated from the formula, 



e 2 = 1 - (N 3 /NJ 2 , 



where N 2 /N e is the ratio of zero up-crossings to wave crests. Epsilon, e, is 

 also developed and discussed, in terms of the moments of the wave spectrum 

 (Cartwright and Longuet-Higgins , 1956), and can be used as a rough measure 

 of the irregularity of a wave record (Draper, 1966). 



The average elevation of the runup crests, R, and the maximum observed 

 runup elevation, R(max), are the two runup parameters given in Table 3; 

 both elevations are referenced to the Stillwater level. R has been 

 extensively used in studies of runup caused by monochromatic waves 

 (Saville, 1956; Savage, 1958). R(max) is of interest because it is 

 generally the extreme values of runup that are needed for design purposes. 

 The two runup parameters also provide a useful way to compare runup caused 

 by monochromatic and irregular waves. Other runup parameters, such as 

 the elevation exceeded by 2 percent of the runup crests (van Oorschot and 

 d'Angremond, 1968), are not tabulated. The record lengths used in this 

 study were too short to allow meaningful interpolation or extrapolation of 

 the runup distributions for extreme values. 



Table 4 gives some data to supplement Table 3, i.e., average and maxi- 

 mum wave heights, and the temporal distribution of runup. 



