3 . Se asonal Changes April 1973 - October 1973 . 



Beach profile measurements after April 1973 indicate that the 

 upper foreshore of Torrey Pines Beach began to accrete and construct a 

 new summer berm. Beach profile and reference rod measurements made on 

 11 May and 6 June 1973 show accretion on all three range lines with the 

 initial onshore movement being the development of a bar at -3 feet 

 (-1 meter) and the progressive accretion of sand at higher elevations on 

 the foreshore to form a new subaerial berm. Figure 10 shows this pro- 

 gressive onshore movement of sand at North Range during April to Septem- 

 ber 1973. The source of the sand accreting on the beach face was from 

 the area immediately offshore at depths of less than -33 feet (-10 meters) 

 as shown by the interrrelation of berm crest progradation and erosion 

 at the shallow reference rods (Figures 6a, b, and c) . 



The summer beach configuration in 1973 was best typified by the 

 profiles measured on 25 October 1973 when the berm crest had prograded 

 farthest seaward and the foreshore increased in slope. Examination of 

 the 25 October 1973 profile at North Range (Figure 9) shows the beach 

 configuration during the summer season. Approximately 1,300 cubic feet 

 per foot (121 cubic meters per meter) beach length accreted on the beach 

 face while 770 cubic feet per foot (72 cubic meters per meter) beach 

 length were eroded from depths of -10 to -20 feet (-3 to -6.1 meters). 

 Profiles measured on the other two range lines show similar changes 

 during this period. 



4 . Seasonal Changes November 1973 - April 1974 . 



The summer beach profile configuration shown by the 25 October 73 

 profile at North Range (Figure 9) remained until the occurrence of 6-foot- 

 high breakers coincident with a +7 foot (2.1 meters) high tide over 7 and 

 8 January 1974. This period of high waves caused the rapid recession of 

 the subaerial berm and reduction in slope of the beach foreshore. The 

 extreme high tides enabled the high breakers to overtop the berm crest 

 and quickly erode the subaerial beach. 



Following this occurrence of high waves, two other periods of high 

 waves and a storm occurred during the spring causing only minor further 

 modification of the beach profile configuration. Figures 6a, b, and c show 

 the change in the position of the berm crest and sand level change at the 

 offshore reference rod stations during the winter and spring of 1973-74. 

 Final winter beach profile configuration is shown by the 4 April 1974 

 -rofile at North Range (Figure 9), with the farthest landward recession 

 jf the berm crest and gentlest foreshore slope. Profiles at the other 

 three range lines also had similar winter season configurations. 



Comparison of the 25 October 73 summer profile and the 4 April 74 

 winter profile at North Range shown, in Figure 9, indicates the maximum 

 seasonal sand level changes. The volume of sand eroded from beach face 

 was approximately 400 cubic feet per foot (57.4 cubic meters per meter) 



27 



