water level) damaged the structure. Effects of the high water level on the 

 structure were amplified by large waves which included ice chunks and debris. 



21. Side-scan sonar surveys and SCUBA diving inspections were used to 

 assess the underwater condition of the dolos cover and stability of the break- 

 water's toe berm. A Klein Associates 500-kHz side-scan system was used in 

 April 1981, July 1982, and July 1984 to conduct surveys of the dolos rehabil- 

 itated portion of the breakwater and several other structures in Cleveland 

 Harbor. For comparison, several runs with a 100-kHz towfish were made during 

 the 1982 surveys. A more detailed discussion of the comparison between the 

 two frequencies can be found in Part V. In addition, Kucharski and Clausner 

 (in preparation) discuss use of various frequencies for various applications. 



22. The results of the first two side-scan sonar surveys (April 1981 

 and July 1982) are presented in Patterson and Pope (1983). An additional 

 survey was conducted in July 1984. The intent of the side-scan sonar survey 

 portion of the monitoring program was to document changes in the underwater 

 condition of the dolos cover. During the first survey it became apparent that 

 side-scan sonar could only be used as a means of obtaining a qualitative 

 record of the slope and toe characteristics of the structure. A dolos cover 

 has certain characteristics (i.e., random placement, high unit relief and 

 small shape, and high void-to-unit ratio) which make it difficult to identify 

 individual, in-place, units and evaluate their condition. Lessons learned 

 during the April 1981 survey were used to improve results of the July 1982 

 survey. For example, vessel size and power were increased, allowing more 

 stability in the wave environment (from a 17-ft single engine outboard to a 

 21-ft twin engine vessel). Also, a short range microwave positioning system 

 was used, and operational techniques were well documented to allow duplication 

 in future surveys. A SCUBA diving survey was recommended for 1983 to check 

 the observations and preliminary evaluations made from the side-scan sonar 

 survey . 



23. In August 1983 two dive teams inspected portions of most of the 

 rehabilitated breakwater. General observations made by the divers confirmed 

 several interpretations about the dolos cover which had been made based on the 

 side-scan records. The steep toe and irregular slope were present in the two 

 side-scan sonar record sets suggesting that these characteristics were the 

 result of initial underwater placement. 



24. A third underwater inspection consisting of a side-scan sonar 



18 



