maximum influence on the slope through a lag in time of between k and 8 

 ho-urs^ and apparently to a lesser extent hetween l6 and 20 hours. Mean 

 grain size of the "beach slope in the shoaling-wave zone is found to de- 

 pend upon the combination: mean bottom slope^ wave period, wave steepness, 

 wind velocity parallel to shore, angle of wave approach, and tidal-current 

 velocity, and this combination is most influential after an 8-12 hour lag 

 in time. When mean slope, the most-dominant independent variable, is 

 ■removed from the analysis, water density and tidal- current velocity appear 

 as the most influential variables on mean grain size. Wind velocity 

 parallel to shore is believed important because it will influence the 

 velocities of the tidal currents that flow parallel to the shore in the 

 study area. Angle of wave-front approach may at times significantly 

 augment or decrease tidal-current velocities near the bed and thereby the 

 sizes of particles moved. Wind velocity onshore and offshore at times 

 interlocks with water density, as density varies when stratified shelf 

 waters undergo turnover. Fluid drag velocities vary as water density 

 varies, and differing sizes of particles will be moved. 



Net deposition on the lower foreshore during June and July is most 

 influenced by slope of the foreshore. Wave period, wave height, wind 

 velocity on-shore, angle of wave approach, and water density are variables 

 that form the most- influential combination when in conjunction with lower 

 foreshore slope. This combination expresses itself 8 to 12 and 20 to 2k 

 hours prior to the low-tide time of measurement of net deposition; that 

 is, during times of rising tide. The regression analysis suggests that 

 net erosion on the foreshore is not nearly as much influenced by beach 

 slope angle as is net deposition, but that lower-foreshore slope is still 

 the most consistently important variable to net erosion through time. 

 The combination of five variables suggested as most influential to net 

 erosion during Jime and July includes lower-foreshore slope, wave period, 

 wind velocity offshore, angle of wave approach, and depth to the water 

 table at the top of the uprush. Of secondary importance, and manifest- 

 ing at times of falling tide, is the combination made up of lower fore- 

 shore slope, wave period, wave height, and angle of wave approach. 



Problem areas reviewed in the study are related to redundant and 

 noisy data and to the linear model used. Descriptions of the regression 

 techniques for the linear and higher-order models are also given. 



INTRODUCTION 



General Considerations 



Study of the beach-ocean-atmosphere system under natural field 

 conditions progresses from initial descriptive studies, consisting mainly 

 of masses of seemingly unrelated observations, to the analysis of "cause- 

 and-effect" (process-and-response) relationships between oceanic and 

 atmospheric forces and their resulting products, the beaches. While in 

 the simplest sense it is possible to choose some intuitively rational 

 group of environmental processes that act as causal factors, and a like 

 group of environmental responses that act as effects, this simple picture 



