OBSERVER 

 ed for an observation plotfor 



■ 180 line on the 



NOTE: If a pier 



rail parallel lo the centerlme of the pier, site along the crest of the 

 breaking waves and record the ongle observed. 



Figure 4. Protractor on back of LEO form which is currently being 

 used to obtain wave direction. 



slope, and rip current and beach cusp spacings. Monthly means, standard devi- 

 ations, the number of observations taken, frequencies of occurrence (in per- 

 cent), and the number of observations of calm conditions are also presented. 

 For example, the first column in Figure 3 represents the summary of LEO obser- 

 vations made for the month of January 1970 at site 05004, Natural Bridges, near 

 Santa Cruz, California. During January, the average breaker height was 3.08 

 feet (0.9 meter) and the standard deviation of the observations was 1.42 feet 

 (0.4 meter); these values are based on 59 observations made during the month. 

 The mean and the standard deviation of the wave period during January were 

 11.45 and 1.86 seconds, respectively, based on the 59 observations. 



During January 1970 the compass sector method was being used and all waves 

 were observed to approach from the south. The coastal sector method was 

 adopted about mid -April 1970. This method gives a better resolution of wave 

 direction than does the compass sector method, a major factor in the decision 

 to modify the method. Note that for the months when the coastal sector method 

 was in use (Fig. 3, April through November), a large majority of waves were 

 in sector 3 indicating shore-normal or nearly shore-normal wave approach. This 

 lack of resolution between upcoast and downcoast wave propagation and the re- 

 sulting direction of sediment transport by longshore currents led to the sub- 

 sequent adoption of the protractor method. The majority of breakers observed 

 in January, 83.05 percent, were of the spilling type. Plunging and surging 

 waves comprised 10.17 and 6.78 percent, respectively, of the observations. 

 Calm conditions were not recorded. Longshore current observations indicated 

 that the net average current was 0.06 foot (0.02 meter) per second. This 

 represents the average of both positive (upcoast) and negative (downcoast) 

 current velocities; hence, a zero or near-zero value does not imply that the 

 average current speed was close to zero but rather that the vector average was 

 close to zero. The gross mean is the average of the absolute values of the 

 observed current speeds. For January this value was 0.19 foot (0.06 meter) 



15 



