indicated a significant reduction in wave heights for the improvement plans versus 

 existing conditions for the 27-m-long (90-ft-long) vessel. Plan 9 resulted in 

 similar wave heights as existing conditions for the 30-, 183-, and 210-m-long 

 (100-, 600-, and 630-ft-long) vessels, and Plan 10 revealed similar conditions for 

 the 183- and 210-m-long (600- and 630-ft-long) vessels as existing conditions. 

 For the 30-m-long (100-ft-long) vessel, however, Plan 10 wave heights were 

 slightly larger than existing conditions. Results also indicated that the smaller 

 vessels (27- and 30-m-long (90- and 100-ft-long)) moving at greater speeds 

 produced the largest wave heights in the harbor for existing conditions as well as 

 for Plans 9 and 10. Greater wave heights occurred for existing conditions for 

 southbound vessels entering the St. Clair River, whereas larger wave heights 

 occurred for Plans 9 and 10 for northbound vessels leaving the St. Clair River. 



Sediment-tracer patterns downstream of the harbor were monitored during the 

 conduct of the experiments. The typical movement of sediment-tracer material 

 and subsequent deposits along the shoreline downstream of the harbor are shown 

 in Photo 157 for existing conditions. Visual observations revealed similar 

 patterns in this vicinity for Plans 9 and 10. The deposits, however, were not as 

 heavy since less material moved around the structure in the same time frame of 

 the experiments. 



Typically, when structures are installed along a shoreline, accretion occurs on 

 the updrift side, and erosion normally occurs downdrift of the structure. The 

 model was constructed as a fixed bed, and erosion could not be determined. The 

 area immediately south of the harbor, however, currently experiences erosion (as 

 evidenced by the exposure of the steel sheet-pile tie rods). The construction of the 

 proposed improvements probably will not alleviate this condition. Therefore, it 

 may be necessary to nourish this area. 



Wave heights for the raised breakwater of Plan 1 1 indicated it was not 

 effective in reducing wave heights in the harbor for typical storm-wave conditions 

 (1.22-m (4.0-ft) waves). For 2.07-m (6.8-ft) wave conditions, however, Plan 11 

 resulted in wave-height reductions ranging from 0.03 to 0.15 m (0.1 to 0.5 ft) in 

 the harbor. Of the improvement plans with absorbers installed in the harbor 

 (Plans 12-16), Plan 14 appeared to be the most effective in reducing wave heights 

 in the harbor. Wave heights in the harbor for 1.22-m (4.0-ft) waves were reduced 

 from 0.0 to 0.06 m (0.0 to 0.2 ft). For 2.07-m (6.8-ft) waves, wave heights were 

 reduced from 0.09 to 0.24 m (0.3 to 0.8 ft) in the harbor for Plan 14. 



60 Chapter 6 Physical Model 



