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

    Noosa Spit SEMP Final Report                                                                               99
    Proposed Implementation Pathway




5.2           Proposed Trigger-based Management Approach
              In the context of the current project, the unacceptable impact is a breakthrough of Noosa Spit at Dog
              Beach. Two triggers for enhanced management action are proposed:

              • Tigger 1: Limited recreational beach width at Dog Beach and loss of vegetation (fallen trees)3

              • Trigger 2: The width of vegetated land above high water has narrowed to 20 m or less

              Upon realisation of the first trigger, implementation of beach nourishment and sand plugs (i.e. the
              preferred option based on the MCA presented in Section 4.3) is proposed. This action is intended to
              remain the preferred management strategy until it is no longer sustainable and/or delivering benefits
              to Council and the community. It is anticipated that the works would be repeated several times
              between now and 2040 and help to mitigate the risk of a breakthrough event.

              The second trigger represents significant narrowing of The Spit width at Dog Beach and signals that
              the beach nourishment strategy is not performing as intended. A notional 20 m width of land above
              the high water mark represents the likely minimum development footprint required for land-based
              construction of a seawall or similar shoreline protection structure. The trigger-based approach is
              designed to avoid a seawall for as long as possible and only calls for consideration of this action if
              beach nourishment is unable to maintain the risk of a breakthrough at an acceptable level.

              The three key stages of a proposed implementation plan are summarised in Table 5-1 and illustrated
              in Figure 5-2. The proposed actions are triggered when the approved activities of the current stage
              of management are no longer maintaining the risks to an acceptable level. The ongoing beach
              monitoring program and visual inspection of the shoreline can be used to assess the current stage
              of management and determine whether planning for subsequent actions should commence. Stage
              2 of the proposed plan could commence immediately, with the current condition of the shoreline
              suggesting that Trigger 1 has been reached (see bottom panel of Figure 5-2). Implementation of the
              proposed beach nourishment and sand plugs would effectively widen the beach and monitoring
              would then focus on identifying when the Trigger 1 condition returns, thereby prompting the planning
              for a subsequent nourishment and sand plug campaign to reinstate the beach width. Ongoing
              resilience building actions, including revegetation and habitat management, are expected to continue
              as part of routine maintenance.




3
    The Trigger 1 shoreline position is approximated in Figure 5-2 using the HAT contour in 2016




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