1. Seasonal Changes June 1972 - October 1972. 



This study was initiated at a time when Torrey Pines Beach was 

 undergoing the change from a winter configuration to a summer configur- 

 ation. The first beach profiles were measured on 6 June 1972 at which 

 time the beach had developed a definite berm for the full length of the 

 study area. During the months of July, August, September, and October 

 the beach continued to accrete on the foreshore at all three range lines. 

 This accretion of the foreshore caused the subaerial beach to widen and 

 the berm crest to move seaward. The most likely source for the sand 

 deposited on the beach foreshore was from immediately offshore at depths 

 of -20 feet (-6.1 m) or less, as indicated by the progressive erosion of 

 the 16-foot (4.9 m) reference rods on South Range (Figure 6a). Similar 

 erosion at shallow depths also occurred on North and Indian Canyon Ranges, 

 although the magnitude and progressive removal of sand is not as apparent 

 (Figures 6b and 6c) . 



Profiles measured on 23 October 72 are representative of the fully 

 developed summer beach configuration in 1972. These profiles were char- 

 acterized by a sharp berm crest at all three range lines that separated 

 a wide flat backshore from a steeply sloping foreshore. The foreshore 

 slope gradually decreased seaward to form a relatively flat terrace 

 extending offshore from the MSL intercept to about -5 feet (-1.5 meters). 

 The seaward edge of this terrace is marked by a slight increase in the 

 profile slope at a depth of -5 to -10 feet (-1.5 to -3 meters) where the 

 gradual decrease in slope continues out onto the shelf. Formation of 

 the summer beach profile configuration was a gradual process of sand 

 accretion on the beach face and erosion at shallow depths seaward of 

 the surf zone over the period of several months. 



2. Seasonal Changes November 1972 - April 1973 . 



The summer beach profile configuration described in the previous 

 section remained intact until IS November 72 when a storm passed through 

 the study area over a weekend. This storm brought considerable precipi- 

 tation, high winds and waves coincident with the spring high tides in 

 the month of November. A beach profile survey was made of the three 

 range lines on 21 November 72 immediately following the storm to document 

 modification to the beach. The 21 November 72 profiles indicated that 

 the pronounced berm that had developed on all three range lines was com- 

 pletely removed and the beach was cut back up to 100 feet (30 meters) . 

 Erosion on the upper beach was accompanied by sand accretion immediately 

 offshore in depth of -10 to -30 feet (-3 to -9 meters). Reference rod 

 measurements made with this survey show accretion in excess of 1 foot 

 (30 cm) on North Range completely covering the rods at a depth of 16 feet 

 (4.9m). 



Figure 7 is a comparison of the October and November 1972 beach 

 profiles at North Range which indicate that approximately 530 cubic feet 



20 



