2018-05-14 GC Agenda Attachment 1 to Item 6 Lake MacDonald Dr Community Reference Group Investigations Report

CRG stakeholders raised concerns about the impact these pipes may be having on flood levels. To
investigate these concerns the upgraded flood model was run for a moderate and major flood
event with and without the pipes included in the model. For the simulation which included the
pipes, the model configuration assumed a complete blockage of flows in the main channel beneath
the pipes and across the pipe profiles.

The flood model results for both the moderate and major flood events showed no change to peak
flood levels at Highland Drive due to the presence of the water supply pipe. Refer to Figure 19
and Figure 20 for flood model results graphed as water level verses time.




             No increase in
             peak flood levels




          Small increase in
          flood levels as
          water rises over
          the pipes.




Figure 19: Flood model results for moderate flood event




Lake McDonald Flooding Community Reference Group Report                                  Page 34