SAND LEVEL CHANGES ON TORREY PINES BEACH, CALIFORNIA 



Charles E. Nordstrom and Douglas L. Inman 



I. INTRODUCTION 



1. Objective of the Study. 



The principal objective of this study was to measure beach profiles 

 along a straight beach with uncomplicated offshore bathymetry that is 

 exposed to ocean waves from all offshore directions. Emphasis in this 

 study was placed upon the accurate measurement of beach profiles in order 

 to determine changes in profile configuration caused by wave action. 

 Profiles were measured from the beach backshore seaward to a depth of 

 about 60 feet (18 m) at monthly intervals for a period of 23 months. 

 Additional measurements were made following storms and periods of high 

 waves in order to document the extent of profile modification associated 

 with these periodic events. Daily visual observations and measurements 

 by pressure sensors provided a record of the waves incident to the beach 

 during the duration of the study. Comparison of the profiles from month 

 to month and seasonally was made to determine the erosional and deposi- 

 tional parts of the profile and the volumes of sand involved in onshore- 

 offshore transport. 



2. Previous Work . 



Many studies have been made of the changes in beach profiles under 

 waves; however, most field data are difficult to interpret in terms of 

 seasonal changes in configuration and onshore-offshore sand transport 

 because of the inaccuracy in the measurements. Most beach profiles are 

 only measured from the backshore seaward into the surf zone, usually ending 

 near the mean sea level datum. This type of data is useful for document- 

 ing changes in the beach foreshore and sand levels on the subaerial beach 

 but does not document the onshore-offshore sand transport. In order to 

 adequately measure the actual changes in profile configuration and onshore- 

 offshore transport, the beach profile must be accurately measured to the 

 seaward limit of significant sand movement. 



Studies of sand level changes on southern California beaches have 

 been made by Shepard (1950), Shepard and Inman (1951), Inman (1953), 

 Brunn (1954), and Inman and Rusnak (1956) . However, of these previous 

 studies, only Inman and Rusnak (1956) made accurate measurements of sand 

 level changes over the offshore segment of the profile. The Inman 



