PART IV: CURRENTS 



58. Surface current speed and direction at the FRF are influenced by 

 winds, waves, and, indirectly, by the bottom topography. The extent of the 

 respective influence varies daily. However, winds tend to dominate the 

 currents at the seaward end of the pier, while waves dominate within the surf 

 zone. 



Observations 



59. Near 0700 hours daily observations of surface current speed and 

 direction were made at (a) the seaward end of the pier, (b) the midsurf 

 position on the pier, and (c) 10 to 15 m from the beach 500 m updrift of the 

 pier. Surface currents were determined by observing the movement of dye on 

 the water surface. 



Results 



Present year 



60. Spatial variation. Figure 26 shows the daily 1985 measurements at 

 the beach, pier midsurf, and pier end locations. Since the relative influ- 

 ences of the winds and waves vary with position from shore, the current speeds 

 and, to some extent, direction vary at the beach, midsurf, and pier end loca- 

 tions. Magnitudes generally are largest at the midsurf location and lowest at 

 the end of the pier. Annual mean currents (Table 8 and Figure 27) were 

 directed southward at the beach location and near zero at the pier end and 

 midsurf locations. There was a strong tendency for more northward directed 

 currents at the midsurf locations than at the beach from April through 

 November. 



61. Temporal variation. During January through March the currents were 

 most often southward, though frequent reversals were observed at the seaward 

 end of the pier during March. For April there were more northward currents at 

 the midsurf than at the beach. May and June had frequent reversals, and the 

 monthly means were low. During August, October, and November there were pre- 

 dominantly northward currents at the midsurf while at the beach there were 

 frequent reversals. Currents were directed southward during December. 



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