for 2.6-m (8.5-ft) waves indicate a runup value between 4.9 and 5.2 m (16 and 

 17 ft) would occur (based on Shore Protection Manual predictions); however, 

 massive overtopping actually occurred that resulted in destruction of the apron. 

 Local forecasts indicated winds of 50 knots and seas of 9.1 m (30 ft) on 

 3 November 1994. Based on these comparisons, the hindcast data appear to have 

 under-estimated wave conditions at the site. As stated earlier, in general, trends 

 indicated larger waves occurred with higher runup values and wave overtopping, but 

 absolute values of the wave heights generated by the hindcast model appeared low. 



Bathymetric data obtained in and adjacent to the harbor in September 1986 

 (prior to construction of breakwater improvements) are shown in Figure 24. Note 

 the 10.4-m (34-ft) el scour hole adjacent to the head of the breakwater. The scour 

 hole formed after construction of the original 229-m-long (750-ft-long) breakwater 

 in 1985. It was monitored by CENPA and did not tend to undermine the breakwater 

 foundation. Depths adjacent to the vertical-walled, concrete caisson City Dock were 

 dredged to greater than 6.1 m (20 ft). Though not shown in the bathymetry, 

 CENPA noted that the cove appeared to begin filling in after initial breakwater 

 construction with accretion along the southeast shoreline of Village Cove. At one 

 point the cormecting charmel between the cove and saltwater lagoon was plugged 

 and subsequently artificially reopened. 



Bathymetric data obtained in August 1992 (after breakwater improvements) are 

 shown in Figure 25. A 10.4-m (34-ft) scour hole formed adjacent to the head of the 

 new main breakwater extension similar to the one formed after the original break- 

 water was constructed. The scour hole did not appear to have significantly 

 undermined or impacted the stability of the structure head. Depths in the harbor 

 between the northernmost dock and City Dock were greater than the 5.5-m (18-ft) 

 authorized federal channel and maneuvering area, and therefore, dredging was not 

 required after construction. LxK;al interests did, however, dredge an area in the 

 harbor adjacent to the TDX dock. Note the change in contours north of and adjacent 

 to the detached breakwater. Sediment began accumulating against the structure. 



Contours of bathymetric changes that occurred between the September 1986 and 

 the August 1992 surveys are shown in Figure 26. These contours show fill and 

 scour conditions in and adjacent to the harbor. The figure shows a 3.7-m (12-ft) 

 scour hole had formed adjacent to the head of the outer breakwater. In addition, 

 acCTetion up to 4.3 m (14 ft) had occurred adjacent to the north side of the detached 

 breakwater. An underwater spit had formed north of the west end of the detached 

 structure and has the potential to migrate across the chaimel. Accretion of 3 m 

 (10 ft) occurred adjacent to the south side of the detached breakwater which 

 suggested sediment may be moving through the structure. Inside the harbor, the 

 scour north of the TDX dock was due to dredging by local interests. Also, the scour 

 hole formed by the original 229-m-long (750-ft-long) outer breakwater appeared to 

 be filling. This may be due to settlement of suspended sediment caused by vessel 

 prop wash, dredging operations, and/or hydrodynamic conditions. The August 1992 

 survey did not include bathymetry in the area in the lee of the east end of the 

 detached breakwater and adjacent to the shoreline inside the harbor. 



32 



Chapter 2 Monitoring Program 



