six at a time are shown in appendix B (tables B1-B6), and the five weakest, 



for lag periods 1, 'i, 5^ and G, in tables B7, b8, B9 and BIO. Frequency 



tables of the computer output for lag periods 2., Z, 5, and 6 are shown 

 in appendix tables Bll, B12, BIB;, and BlU. 



Discussion . --Considering the strongest combinations of Xs taken six 

 at a time (tables B1-B6), it is noted that variable Xl, lower foreshore 

 slope, always contributes to these strongest combinations. In an analysis 

 (not presented here) of the interactions of the lower foreshore slope with 

 twelve variables of the environment, it was noted that the strongest com- 

 binations of five_Xs at a time, in the most-influential lag period, con- 

 sisted of Hq, a, V, p, and R. It would seem reasonable to expect that 

 some or all of these variables would also be of significance in this analy- 

 sis for Jj.. (The corresponding Xs in the analysis for Jf are Xh, X9, XIO, 

 Xll, and perhaps X12 and X13.) Tables B1-B6 show a tendency for most of 

 these variables to enter into the strongest combinations, but most also 

 enter into the weakest, and there is little consistency from one lag period 

 to the next. 



Assuming physical validity for an analysis such as this — for changes 

 in a surface that crosses two differing dynamic zones and using a data set 

 that is noisy and redundant — the following few points should be noted. 

 Beach slope is a controlling factor in deposition on the lower foreshore, 

 as net deposition is measured at low tide, after two tidal cycles. (it is 

 understood that grain size of the slope material is also of great importance.) 

 The rate of fall of the still-water level is of some significance during 

 the two periods of falling tide (lag periods 1 and U) . The rate of rise of 

 still-water, however, has no significance during the two periods of rising 

 tide. Depth to the water table has the greatest effect on net deposition 

 around the time of high tide or during falling tide. The effect of the 

 longshore current enters into the strongest combinations of variables taken 

 six at a time during only one lag period. This is not surprising, inasmuch 

 as the longshore current serves largely to transport material parallel to 

 the shoreline. Wind velocity appears to have significance to net deposi- 

 tion during the falling tide immediately prior to the time of low-tide 

 measurements. Wind blowing offshore may set up a weak sea-surface current 

 that will aid in the removal of fine sand suspended in the breaker zone 

 but, at the same time, not cause an equal quantity of sand to be transported 

 onshore in the corresponding return flow on the bottom. As a result of 

 wind blowing onshore, large particles may be transported out of the breaker 

 zone by the seaward return flow of water (cf . King, 1959; P- 207-213) on 

 the bottom. Local winds in onshore and offshore directions will also in- 

 fluence the form of the incoming swells, as discussed in the section on 

 the longshore currents. 



Among the wave variables, Hq, and occasionally Hq/Lq, are the most 

 important to net deposition. Statistically, water density plays a role 

 (tables B2 and B3) during the first part of the tidal cycle immediately 

 prior to measurement of J^. Presumably, p affects the rates of particle 

 movement by its effect on fluid drag velocities and tiirbulence at the bed. 



38 



