change the adsorption and attenuation characteristics of the water which vary 

 daily and throughout the year. Daily water visibility measurements made at 

 the seaward end of the pier are shown as a function of time in Figure 25. 



128. The daily visibility is highly variable. Fifty percent of the 

 time the surface visibility at the seaward end of the pier is less than 2 m 

 (Figure 26). Visibility in excess of 6 m occurred about 10 percent of the 

 time (or 30 days) during 1980, predominantly in July, August, and September. 

 The greatest range of visibility occurred in August when greater than 5 m 

 changes over 2A hours were not uncommon. Visibility varies much the same as 

 surface water temperature (see tabulation, paragraph 125); onshore winds tend 

 to bring clearer surface waters to the coast, and offshore winds produce up- 

 welling of more turbid bottom water. 



Current Data 



129. Currents measured at the seaward end of the FRF pier and 500 m up- 

 drift of the pier on the beach are discussed in this section. Monthly and 

 annual summaries as well as time histories of the daily values (Figures 27 and 

 28) are presented. The monthly average surface current speeds (see tabulation 

 on page 67) were strongest toward the south at the pier end during the winter 

 months. These currents were caused by predominantly northerly winds and per- 

 sistently high wave conditions. From April through September, the winds blew 

 predominantly from southerly directions and more frequently produced north- 

 wardly moving currents as was especially evident in the wave-induced beach 

 currents . 



130. Current speeds were generally higher and the seasonality of the 

 current direction was more evident on the beach than at the seaward end of 

 the pier. 



131. Peak current speeds were generally higher and more frequent for 

 southward flow than for northward-moving water except for the persistent 

 northerly currents on the beach during the summer months (Figure 28) . 

 Survey results 



132. Weekly pier surveys from both sides of the pier and time histories 

 of bottom elevations at selected locations along the pier are presented in 

 Appendix C. 



133. Bathymetry. Figure 29 is a contour diagram of the 1980 beach and 

 nearshore bathymetry; the offshore data are not included due to the question- 

 able accuracy of the depth information. 



63 



