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

 Noosa Spit SEMP Final Report                                                                                95
 Shoreline Erosion Mitigation Options




4.3.6    Option 5: shore parallel seawall
         The indicative minimum footprint for construction of a shore parallel seawall (or similar coastal
         protection structure) is illustrated in Figure 4-17. This footprint is defined by a ~20 m buffer from the
         HAT contour on the southern side of The Spit, noting that the actual footprint would need to be
         determined as part of a concept and detailed design study. It may be possible to construct the seawall
         in stages; however, this would need to be carefully planned given the restricted access for land-
         based equipment.

         Regarding effectiveness, a properly designed and constructed seawall is expected to reduce the risk
         of a breakthrough to an acceptable level. The whole of life cost estimate for this option is $4.1M with
         annualised costs around $200,000/year. This includes beach nourishment as part of the capital
         costs.

         This option accepts the ongoing loss of dune and terrestrial habitat to erosion and would likely cause
         further losses during the construction phase.

         The social values associated with Dog Beach would be gradually lost. Ongoing nourishment of the
         shoreline could be used to maintain beach amenity in front of the seawall; however, the seawall
         would be designed to be stable in a fully exposed condition (that is, beach nourishment would not be
         required for the structure to perform as intended).

         The risks to Council are generally low to medium and manageable. The exception being the relatively
         large investment of public funds and the perception of benefiting a small number of private properties.
         Full details of the risk assessment results are provided in Appendix D.




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