b. Structure Location . In response to the request for a site map, most 

 operators drew a quick sketch of their facility and the FB's position. The 

 redrawn maps provided in the report are helpful in understanding the orien- 

 tation of the FB relative to the shoreline, but in no case should the posi- 

 tioning of the map elements be taken as precise or the representation of the 

 protected facility be considered exact, for such accuracy is impossible from 

 a simple, hand-drawn sketch. 



c. Operational Problems Encountered . The survey asked the respondents 

 to rate how severe various problem areas were in regards to their FB. The 

 answers are clearly subjective (e.g., the problem of a breakwater trapping 

 floating debris may be viewed as a major one by an operator sensitive to its 

 waterfront appearance, while a second person may view it as a minor nuisance) 

 and are occasionally conflicting due to the unintended overlap of certain 

 problem areas. Nonetheless, based on information contained elsewhere in the 

 survey, it usually has been possible to portray a representative picture of 

 the problems encountered. 



d. Transmission Coefficient . The transmission coefficient is the ratio 

 of the wave height on the leeward side of the FB to the wave height on the 

 exposed side of the structure. Thus, if 1.5-m (5.0 ft) waves are suppressed 

 by an FB and reduced to a height of 0.9 m (3.0 ft), the transmission coef- 

 ficient is 0.60. (Note that since the energy in a wave system is propor- 

 tional to the wave amplitude squared, a 0.60 transmission coefficient means 

 that 64 percent of the wave energy is being dissipated by the FB.) In most 

 cases, the reported transmission coefficients are much lower (i.e., the FB 

 is much more effective) than those reported in carefully monitored studies. 

 This effect is probably due to an enchantment with the structure on the part 

 of the operator, distorting the FB's physical effectiveness. Nonetheless, 

 the reported findings are believed to be significant for they represent, 

 albeit in an abstract sense, the satisfaction of the operator with the struc- 

 ture. Consequently, the reported transmission coefficients have not been 

 altered. Furthermore, if it is assumed that this distorting effect is common 

 to most of the responses, then the coefficients are also useful in a compara- 

 tive sense. 



e. Cost . Because many of the FB structures were essentially do-it- 

 yourself projects or have changed ownership since their construction, it is 

 suspected that several of the reported costs are just guesses made without 

 the aid of accurate accounting. In other instances, it is believed that labor 

 costs are underestimated or ignored because of the employment of an in-house 

 work force. Thus, the cost breakdowns given by the respondents should be con- 

 sidered as general indicators of the actual price range. To simplify com- 

 parison of costs between projects, MRM calculated each project's 1980 dollar 

 cost per square meter (and per square foot) of FB surface area through the 

 use of construction-related inflation factors. 



f. Additional Benefits . As with the evaluation of operational problems 

 encountered, the determination of additional benefits provided by an FB is a 

 highly subjective and occasionally arbitrary task. In particular, judging 

 the effect of the structure on sediment movement, shoreline erosion, and water 

 circulation is a difficult, if not impossible, evaluation to make without 

 proper instrumentation and careful recordkeeping. Nevertheless, the benefits 

 perceived by the respondents have been recorded as written, trusting that in 



a qualitative sense their integrated observations are true. 



