Runs G and H (2 mm, coarse sediment) 



The 3-D version of COSMOS used here requires a single representative 

 grain size. The first two series of runs (A-F) were completed with a grain size 

 of 0.2 mm. The SW and NW storm events were then repeated with 2-mm 

 sediment. This coarser grain size is representative of the coarse beachfill 

 derived from upland sources. However, the coarse fraction is generally found 

 only close to shore (see Parson and Smith (1995)) and therefore, the results of 

 these runs are probably only valid for the inner surf zone and upper beach 

 areas. 



The reduction in predicted alongshore transport (compared to the fine grain 

 size) was not as dramatic in these runs as it was for the average annual along- 

 shore transport results (see Table 9). In general, the profiles are more stable, 

 as expected. Therefore, areas of exposed till remain exposed, while sections of 

 buried till are not uncovered. 



Runs I and J (high water level) 



In this series of runs, the 3-D change for the SW and NW storms is pre- 

 dicted under high lake level conditions (the grain size of 0.2 mm represented 

 pre-fill conditions). For the SW storm event, the predicted alongshore trans- 

 port is lower for the southern section from Line R14 to R23 than that predicted 

 with the average lake level conditions (see Table 9). The alongshore transport 

 is reduced by 10 to 50 percent owing to the greater water depths offshore of 

 the revetment. In contrast, the alongshore transport rates for the northern 

 section of the study area shoreline (including the feeder beach and the fillet 

 beach) are increased by about 40 percent as larger waves can reach steep sec- 

 tions of the upper beach under the high lake level conditions. For the SW 

 storm, these changes to the alongshore transport result in greater erosion south 

 of the Waterworks revetment (i.e., Line R12) and at the north end of the 

 feeder beach (Rll), which is balanced by greater deposition along the north 

 feeder beach and fillet beach. 



These trends are reversed for the NW storm results, with increased 

 southward-directed transport in the northern section and slightly decreased 

 southerly transport in the southern section of the study area. As a result, pre- 

 dicted deposition is slightly greater at Lines R12 and R20. 



Runs K and L (pre- and post-fill with 0.5-m marker depth) 



As noted earlier, placement of the beachfill did not change the contours 

 which the incident waves encounter for 3-D Runs D to F. This was a result of 

 the fact that the "marker depth" which delineates the main pathway for along- 

 shore transport was specified as the 2.5-m depth contour, which is located well 

 offshore of the toe of the beachfill. Therefore, Runs K and L were performed 

 with a marker depth of only 0.5 m, which better represented the contour 

 changes created by the beachfill. Evaluations of pre- and post-beachfill 



Chapter 4 Analyses of Coastal Processes and Geomorphology 



49 



