2019-12-16 GC Agenda - Item 5 - Attachment 1 - Noosa Spit Shoreline Erosion Management Plan-Part 1

 Noosa Spit SEMP Final Report                                                                              52
 Numerical Modelling of Entrance Configurations




3.6.2    Impact to Current Magnitude at Dog Beach
         Maps showing the impact to peak tidal current magnitude are shown in Figure 3-20 to Figure 3-27
         and indicate the following:

         • Comparison between the existing and 1987 entrance condition suggest significantly reduced
           erosion pressure at Dog Beach in 1987. During this period the Dog Beach channel was shoaled
           and the dominant flow channel was central during peak flood tide conditions (Figure 3-20) and to
           the north during peak ebb tide conditions (Figure 3-21).

         • The erosion pressure at the western extent of Dog Beach was greater in 2010 compared to the
           existing condition, particularly during peak flood tide conditions (Figure 3-22). This area has since
           been stabilised by the geofabric sand container training wall constructed in 2013. The existing
           peak ebb tide currents through the middle section of the Dog Beach channel are greater in
           magnitude compared to 2010 (Figure 3-23). This demonstrates the ongoing dominance of the
           Dog Beach channel and implies that the works completed in 2013 are only reducing erosion
           pressure along a limited section of shoreline, updrift of the training wall during the flood phase of
           the tide.

         • The breakthrough condition leads to greater current magnitudes at the eastern end of Dog Beach
           during both flood (Figure 3-24) and ebb (Figure 3-25) tide phases. The distribution of currents
           suggests the potential for rapid morphological change at the Spit following a breakthrough event.
           The Noosa Woods area would be expected to narrow overtime and lead to further loss of coastal
           land that protects Noosa Sound and Hasting Street.

         • Following a major flood event, the erosion pressure at Dog Beach associated with tidal currents
           is reduced in comparison to the existing condition (Figure 3-26 and Figure 3-27). Scour during
           the river flooding creates a dominant central channel and reduces flow throughout the Dog Beach
           channel during flood and ebb tide phases.




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