to the beach, Topograpliic surveys showing the changes in sand level in- 

 dicate that beach material migrates seaward during periods of large waves 

 and landward during periods of small waves. The most pronounced changes in 

 sand level occur in depths of less than 30 feet, but some seasonal effects 

 may extend to much greater depths. The greatest change in sediment size 

 also took place from the beach foreshore out to depths of about 30 feet. 

 In this zone the sediments tended to be coarser during the xd.nter and spring 

 when the beaches vjere cut back, and finer in the fall folloi-jing the summer 

 fill. 



The results of laboratory experiments to evaluate the effect of 

 accelerative forces in the orbital current meter system have enabled the 

 conputation of tlie discrepancy in orbital velocity measurements due to 

 virtual mass for various com-binaticns of wave height, period, and depth 

 of water. In general it was fouJid that the error caused by virtual mass 

 was negligible for velocity measurements just outside of the breaker 

 2one, but that the discrepancies increase with decreasing wave period 

 and height and mth increasing water depth. 



Research continues into ways to take fuller scientific advantage 

 of recent developments in techniques and gear for unden-jater diving, ' 



In one such operation, divers forced test rods into the sandy bottom at 

 depths of 30 feet off Scripps Beach more than six months ago. The first 

 major change in bottom lev el, as indicated by the rods, took place later 

 in the fall. It appears that there was a 21- inch fill during a h7-d3j 

 period, 



A paper is in preparation that iriLll discuss a new rrethod for calculat- 

 ing wave intensity along a single ray. 



Ill, New York Univei sity Bi-Monthly Progress Report, 1st report, for 

 period 1 Jan 1953 to 28 Feb 19^37 ^ 



Work on the project began on 1 Febiruary. The three objectives 

 of the contract are (l) the collection of statistical wave data for points 

 in deep water offshore from six selected coastal areas, (2) the develop- 

 nent of an electronic wave analyzer, and (3) the continuation of theoretical 

 investigations concerned xd.th wave phenomenon. 



Statistical Vfave Data . The statistical data available from breather 

 ships has been studied and much data was collected during the time from 

 9 February through 21 FebruaiT on wave conditions over the North Atlantic, 

 This data t-jill be available when needed as a starting point for the des- 

 cription of x-irave conditions at the selected offshore points. 



Theoretical development . Professor Neumann, in connection with other 

 research, has derived a theoretical power spectrum for the waves which 

 shows many inportant points of agreement with the actual sea surface. 

 An iii5)ortant "theoretical work by Rice has been studied and the results of 



12 



