previous high tide and the succeeding low„ It is convenient to keep 

 this dimension flexible because the inter-tidal zone on open ocean 

 beaches may be above or below its predicted position; this is caused 

 by piling up of ?rater on a beach due to wave action, wind drag on the 

 sea surface causing either higher or lower tides - , and changes in sea 

 level due to barometric pressure gradients „ On steep beaches, the re- 

 ference zone may be as narrow as twenty feet while on flat beaches it 

 may be over a hundred feet wide. 



Relationship Between Beach and Sediment Characteristics - A complete 

 discussion of the analysis of the various field data appears in the 

 report Issue No. 2, Series 14 (see Part VI). Briefly, the results of 

 this study show the following information, (a) a generalized distribu- 

 tion of sand size across a beach from the dunes to an offshore depth 

 of approximately 30 feet, (b) typical sand sizes and beach slopes' of 

 Pacific Coast beaches, (c) the changes in beach slope with erosion 

 and deposition, (d) the variation of sand size and beach slope with the 

 degree of protection from wave action, (e) and the relationship between 

 sand size and slope of the beach face . 



Con clusion s - From the results of this comprehensive study of a 

 large number of Pacific Coast beaches, the following conclusions appear 

 reasonable « 



1, Sandy beach-face slopes (reference zone) on U» So Pacific 

 Coast beaches range from 1%A to 1?100. 



2 Median diameter of beach material from the reference point 

 on sandy beaches range upward from 0.17 mm. 



3. As beaches build and erode, the slope of the beach face at 

 the reference point will change considerably, apparently in response 

 to the H/L factor of the waves. An eroding beach will flatten | a 

 building beach will steepen. 



4. Distribution of sand b3>- size along a profile is predictable 

 with reasonable accuracy if the median diameter of the sand at the 

 reference point is known. Large grains are found at points of 

 maximum turbulence; sizes get smaller as turbulence decreases. 



5„ The slope of the beach face is related to the median diameter 

 of the sand and the amount of wave energy reaching that point. The 

 amount of energy is a function. of the refraction conditions; consequent- 

 ly, beaches that are protected are steeper for any given sand size 

 than exposed beaches. 



Investigation of Coastal Sand Movements; Santa Barbara, California 



Introduction - Little is known about many of the factors which in- 

 fluence littoral transport, Basic questions have never been answered, 



10 



