Table 8 



Summary of 3-D Model Runs 



3-D Run 



Storm Event 



Primary Direction 



Lake Level 



Fill Status 



Grain Size (mm) 



Marker Depth (m) 



A 



2 Nov. '91 



SW 



avg. 



pre 



0.2 



2.5 



B 



14 Jan. '92 



NW 



avg. 



pre 



0.2 



2.5 



C 



24 Jan. '92 



W 



avg. 



pre 



0.2 



2.5 



D 



2 Nov. '91 



SW 



avg. 



post 



0.2 



2.5 



E 



14 Jan. '92 



NW 



avg. 



post 



0.2 



2.5 



F 



24 Jan. '92 



W 



avg. 



post 



0.2 



2.5 



G 



2 Nov. '91 



SW 



avg. 



pre 



2.0 



2.5 



H 



14 Jan. '92 



NW 



avg. 



pre 



2.0 



2.5 



1 



2 Nov. '91 



SW 



high 



pre 



0.2 



2.5 



J 



14 Jan. '92 



NW 



high 



pre 



0.2 



2.5 



K 



14 Jan. '92 



NW 



avg. 



pre 



2.0 



0.5 



L 



14 Jan. '92 



NW 



avg. 



post 



2.0 



0.5 



Owing to the great number of output plots generated from the series of 

 3-D runs (11 plots for each of the 12 storms) only the profile change results 

 from run B are presented (see Figure 20). A summary of the predicted net 

 alongshore transport for each of the profile lines for some of the runs is given 

 in Table 9. 



Runs A to C (Initial series) 



The profile change is most pronounced in the 14 January 1992 (NW) and 

 2 November 1991 (SW) events. For the NW event, the alongshore transport 

 values are similar to average annual alongshore transport results; alongshore 

 transport is lower for the southern profiles offshore of the seawall and revet- 

 ment. In other words, there is a reduction in transport moving from north to 

 south, which results in deposition in the southern section, this being particu- 

 larly evident at Lines R12 and R14 (see Figures 20f and 20g). In general, for 

 the northwest and west storms, only 50 percent to 60 percent of the sediment 

 eroded from the feeder beach area is transported beyond R23 (see Table 9 

 comparing results for Lines R12 and R23). Therefore, the deep water that has 

 developed through downcutting offshore of the toe of the revetment in the 

 southern section of the study area acts as a partial trap to sediment moving to 

 the south. 



For the southwest storms, this trend is reversed, with alongshore transport 

 increasing in a northerly direction. This results in erosion between Lines R14 

 and Rll, which primarily affects the ephemeral beach deposit that is located 

 south of the Waterworks revetment. The fact that the Waterworks revetment 

 acts as a partial littoral barrier (i.e., a short groin) is not captured by the 



Chapter 4 Analyses of Coastal Processes and Geomorphology 



41 



