indicated. Wave runup values in excess of 6.1 m (20 ft) occurred on 15 occasions 

 (19 and 22 October; 1, 2, 9, 10, 12, 14, 15, 16, 23 and 26 November; and 10, 11 

 and 12 December 1994) during the monitoring period. Overtopping of the structure 

 also was observed on four occasions (3, 11, 14, and 25 November 1994). Analysis 

 of wave runup on the structure using the videotape methodology proved to be 

 successful except during periods when visibility was low. Since incident wave data 

 were not obtained, it was not possible to correlate runup results with those obtained 

 in the two-dimensional model and/or those predicted by the Shore Protection 

 Manual. 



Wave overtopping rates of 1.7 C/sec/m (0.022 cfs/ft) were calculated from the 

 container in the lee of the main breakwater during the 3-hr period prior to the 

 collapse of the container apron on 3 November 1994. As mentioned previously, as 

 much as 50 percent of the overtopping waves were not collected due to spray and 

 "overshooting" of the container during the storm. Therefore, the actual rates are not 

 quantifiable. It was also noted that significant volumes of water were reaching the 

 road as a result of waves passing through the rubble-mound structure. These values 

 could not be quantified with the equipment setup that was onsite. Waves passing 

 through the structure and overtopping from this storm were obviously unacceptable 

 since they resulted in washing out of the road in the lee of the breakwater. Since 

 incident wave conditions were not known and overtopping rates could not be 

 quantified for this storm event, no attempt was made to correlate overtopping 

 results with the two-dimensional model study results or guidance provided in the 

 Shore Protection Manual. 



Logistical problems were experienced in the delivery of the container and 

 materials for its apron to St. Paul Island. The container was modified, and materials 

 for the apron were prefabricated, on the west coast of the U.S. mainland, since this 

 work could not be done at the remote Alaskan location. These items were shipped 

 to St. Paul Island by barge. Delivery dates to St. Paul were uncertain; however, 

 coordination with the harbormaster resulted in the equipment being off-loaded at the 

 harbor. Originally, plans were to design and construct the apron with a Z-beam 

 steel frame and corrugated metal skin. Welders would have been required to 

 assemble the apron. Since they were not available for hire at St. Paul, the decision 

 was made to prefabricate the wooden frame and assemble it onsite. The apron was 

 not expected to endure the entire storm season, but it was expected that data could 

 be obtained for less severe storms. As stated earlier, it was destroyed during the 

 first major storm of the season. These factors should be considered in future 

 monitoring efforts in remote, high-wave-energy locations. 



Measured wave runup data and observed wave overtopping were correlated with 

 wave hindcast data. On the dates and times when runup values exceeded 6.1m 

 (20 ft), incident wave height data predicted by the hindcast model ranged from 0.5 

 to 4.8 m (1 .6 to 15.7 ft). During periods of observed overtopping, hindcast wave 

 height predictions ranged from 2.3 to 5 m (7.6 to 16.4 ft). Wave periods obtained 

 from the hindcast model ranged from 6 to 15 sec, and those measured from video- 

 tape ranged from 9.7 to 19.7 sec. A specific case compared was conditions on 

 3 November 1994, when the overtopping container apron was destroyed. Hindcast 

 data indicated a wave height of 2.6 m (8.5 ft). Preliminary wave runup calculations 



Chapter 2 Monitoring Program 31 



