Hydraulic Model Studies of the Harbor 



Three-dimensional (3-D) model study 



During 1987, a 3-D model study of St. Paul Harbor, AK, (Bottin and Mize 

 1988) was conducted at WES to: 



a. Study wave and shoaling conditions for the existing harbor. 



b. Determine the most economical breakwater extension configuration that 

 would provide adequate wave protection to the proposed mooring area and 

 docking faciUties. 



c. Provide qualitative information on the effects of the breakwater extension on 

 sediment movement adjacent to the harbor and shoreline of Village Cove. 



d. Develop remedial plans for the alleviation of undesirable conditions as 

 necessary. 



The St. Paul Harbor model (Figure 5) was constructed to a linear scale of 1 :75, 

 model to prototype. It reproduced approximately 4,1 15 m (13,500 ft) of the 

 St. Paul Island shoreline and included the existing harbor (located in Village Cove), 

 and xmderwater topography in the Bering Sea to an offshore depth of 12.2 m (40 ft). 

 A small connecting channel to a salt lagoon (located east of the harbor) was also 

 included in the model as well as the tidal prism of the salt lagoon. The total area 

 reproduced in the model was approximately 1,500 sq m (16,000 sq ft), representing 

 about 8.3 sq km (3.2 sq miles) in the prototype. Figure 6 is a general view of the 

 model. 



Model tests were conducted for 59 improvement plans with variations that 

 entailed changes in the length, alignment, and/or crest el of breakwater extensions, 

 breakwater spurs, and a detached breakwater. An 18.3-m-long (60-ft-long) 

 imidirectional, spectral wave generator, an automated data acquisition and control 

 system, and a crushed coal tracer material were utilized in model operation. A 

 layout of the recommended plan (Plan 47) is shown in Figure 7. The most notable 

 difference between the recommended model plan and the breakwater configuration 

 constructed in the prototype was the width of the navigation opening. The model 

 plan consisted of a 76.2-m-wide (250-ft-wide) entrance opening; however, a 

 91.4-m-wide (300-ft-wide) opening was constructed in the prototype to enhance 

 ease of navigation in and out of the harbor. Also, the length of the detached break- 

 water tested in the model was 335 m (1,100 ft) as opposed to the 296-m-long 

 (970-ft-long) structure constructed in the prototype. 



Wave height tests and wave patterns were obtained for existing conditions and 

 the 59 test plans. Some plans were limited to the most critical direction of wave 

 approach; however, the most promising ones were tested comprehensively for waves 

 from five directions. The U.S. Army Engineer District, Alaska (CENPA) specified 

 that for an improvement plan to be acceptable, maximxmi significant wave heights 



Chapter 1 Introduction 



