stations the volume (milliliter) of sediment retained by the 0.5- 

 millimeter screen was recorded during the sample screening process. 

 This represents the volumetric proportion of coarse sand (larger than 

 0.5 millimeter) found within the core sample. 



Grain-size composition was determined by sieving dried sediment 

 samples through a standard set of Tyler screens (Morgans, 1956). 

 Fractions retained on each screen were weighed and the results expressed 

 in percent of total weight. Median diameter and sorting were computed 

 on the basis of the cumulative distribution curve of the sieved fractions. 



To determine carbon content of sediments, samples were dried and 

 homogenized, and part of the homogenate analyzed for total carbon 

 using a Leco Carbon Analyzer in which carbon is measured as carbon 

 dioxide released upon combustion. A subsample of each homogenate was 

 treated with 1:1 hydrochloric acid and redried. The carbon remaining 

 following acidic carbonate removal is the organic fraction of total 

 carbon. The difference between this organic fraction and total carbon 

 is an index of calcium carbonate (shell fragments) in the sediments. 



Water temperature was measured during the sampling period to the 

 nearest 0.2° Celsius. 



Photos of the intertidal stations were taken to depict beach 

 topography using fixed reference points. Photos used in conjunction 

 with transect lines and a bubble level bar and protractor provided 

 data for estimating beach profiles. 



Wave data were obtained from published reports from the Department 

 of Navigation and Ocean Development (DNOD) , Sacramento, California. A 

 pressure sensor is located at the end of the Imperial Beach pier at a 

 9.3-meter MLLW depth (below MLLW) . 



The data are presented in terms of the total variance, <n^>, which 

 is related to the wave energy per unit surface area (E) : 



E = pg<n2> 



where p is the fluid density and g is the gravitational acceleration, 

 <n^> is listed in units of square centimeters. The significant wave 

 height Hi/3 is estimated from the wave variance <n^> through the equation: 



Hi/3 = 4 <n>2 . 



Beach Replenishment . 



Approximately 765,000 cubic meters of material was pumped onto 

 Imperial Beach between 22 March and 20 June 1977 (see Fig. 1; App. A). 



27 



