per second with a standard deviation of 0.17 foot (0.05 meter) per second. 

 Current observations were made about once a day since only 30 observations were 

 made. Foreshore slope averaged 3.17° with a standard deviation of 1.05° based 

 on 30 observations. There were no observed rip currents or beach cusps in 

 January 1970 at Natural Bridges. 



The last column in the Yearly Summary Report (Fig. 3) gives data values 

 averaged for all the data acquired during the year. 



b. Wind Roses . The wind rose plots represent wind speeds and directions 

 recorded during the entire period of record. An example is shown in Figure 5. 

 Windspeeds are plotted as frequency of occurrence, in percent, according to the 

 compass direction from which they blow. The term "insufficient data" indicates 

 that less than 10 wind observations were taken for that particular month. 



V. OTHER TYPES OF DATA ANALYSES AVAILABLE 



Computer programs in a number of analyses and formats are available that 

 provide various additional statistical summaries of LEO data. These programs 

 will be provided to users on request. Examples of the various data formats 

 follow. 



1. Daily LEO Printouts . 



An example of a daily LEO printout is given in Figure 6. The listing is 

 simply the daily values of the LEO observations presented chronologically for 

 a given month. Each month of data is listed on separate sheets. The date 

 and time of each observation are given along with the values of each data entry 

 made for that series of observations. Each line corresponds to the data entered 

 on a completed LEO form. For example, for the observation made at 1515 hours 

 (24-hour clock) on 3 April 1968 (Fig. 6, second line) breakers 3 feet (0.9 

 meter) high with a period of 20.0 seconds were reported. Surging breakers 

 occurred and the waves were generally approaching from the southwest. The 

 windspeed was 20 miles (32 kilometers) per hour, blowing from the northwest. 

 No currents were observed at this time. (The asterisks indicate that no obser- 

 vation was made; zeros indicate that an observation was made but its value was 

 zero.) 



2. Frequency and Cumulatiye Frequency Histograms of Breaker Height and Period . 



These printouts provide an annual statistical summary of wave height and 

 wave period probabilities. Figure 7 is an example of wave height histograms 

 prepared for data collected between April 1968 and November 1970 at Natural 

 Bridges. Data are tabulated for wave heights at 1-foot (0.3 meter) intervals. 

 For example, Figure 7 shows that 32.6 percent (576 of the 1,765 observations) 

 of the wave height observations made at Natural Bridges fell in the interval 

 2.0 5 H|, < 3.0 where H^ is the breaker height. The lower half of Figure 7 

 shows that 56.1 percent of the waves (991 of 1,765 observations) at Natural 

 Bridges were greater than or equal to 30 feet (9.1 meters). Figure 8 pro- 

 vides similar information for wave periods at 1-second intervals. 



3. Joint and Marginal Probabilities for Breaker Height and Period . 



The probability distribution of wave heights for a given wave period inter- 

 val is available in tables of the joint wave height and wave period probabilities, 



16 



