THE LITTORAL ENVIRONMENT OBSERVATION (LEO) 

 DATA COLLECTION PROGRAM 



by 



Christine Schneider 



I. INTRODUCTION 



Erosion caused by waves and currents acting in the surf zone along much of 

 the coastline of the United States is a constant concern in coastal engineer- 

 ing. Coastal engineers have a continuing need for wind, wave, and nearshore 

 current data in order to describe the sand transport processes in the surf 

 zone and to design coastal works that are both functionally and structurally 

 successful. The use of recording instruments to acquire such data can be very 

 expensive, particularly if the data are required over a broad geographic area 

 and for an extended period of time. 



The Littoral Environment Observation (LEO) Program was established to pro- 

 vide data on coastal phenomena at low cost. Volunteer observers obtain daily 

 measurements of breaker height, wave period, direction of wave approach, 

 windspeed, wind direction, longshore current velocity, and beach slope, and 

 record the presence of beach cusps and rip currents. At some LEO sites, 

 monthly sand samples are also collected from the swash zone. Observers use 

 simple, inexpensive equipment and expendable supplies to obtain the data; for 

 some data such as wave height and direction, observers simply record visual 

 estimates. 



Obviously, with such simple collection methods and the visual estimates of 

 some variables, an individual LEO data set is subject to error. The skill and 

 biases of individual observers have a significant bearing on the validity of 

 the data. Also, the different LEO collection methods have different levels of 

 reliability. For example, the observations of variables such as windspeed and 

 foreshore slope, obtained with the help of simple instruments, are probably 

 more reliable than the observations of wave height and direction based only on 

 visual sightings. 



While individual LEO observations may be of questionable accuracy, a time 

 series of LEO can be useful in statistically describing the environment at a 

 particular site. Statistical descriptions provide valuable information on 

 waves, currents, and longshore sand transport. Observer bias is partially 

 compensated for by reviewing relative changes rather than the absolute value 

 of certain parameters. For example, while the absolute magnitude of longshore 

 transport rates predicted from LEO wave observations may exhibit some error, 

 the relative proportion of upcoast-to-downcoast transport will probably be 

 reasonably correct. 



