2021-11-15 GC Agenda - Item 7 - Attachment 1 - Coastal Hazards Adaptation Plan

            Noosa Shire Council



  The cost-benefit analysis found this option                        potential adverse effects for adjacent properties
  performed poorly with a NPV of -$2.77 billion                      during construction, which may increase the
  for Peregian to Sunshine Beach and -$67 million                    costs of this option even further. In addition, there
  for Teewah Beach. While the expected property                      remains uncertainty regarding material costs and
  and asset benefits are high because the seawall                    construction costs, and material supply in terms
  would provide a defence from erosion, the                          of access to feasible rock supply.
  implementation costs would be very high.
                                                                     Even without these broader socio-economic costs,
  The establishment of a physical barrier of the                     the financial cost of implementation would be
  proportions required to reduce the risk to the                     significant, given the level of protection required
  built environment would impair the natural coastal                 to withstand a major storm event such as one
  processes of sand replenishment and the natural                    with an average recurrence interval (ARI) of 100
  function of the adjacent dune systems, and thus                    years (i.e. occurs on the average once in every
  impact scenic amenity, tourism, recreational, and                  100 years)26. The required height, required length,
  environmental attributes that are considered of                    land tenure arrangements (e.g. where should it
  high value to Noosa. These areas are currently                     be located, who would maintain it), would lead to
  characterised by their natural sandy, vegetated                    excessive construction and ongoing maintenance
  beachfronts, uninterrupted by hard walls. The loss                 costs.
  of these wide sandy beaches would also impact
                                                                     Depending on the funding arrangements, a
  the broader economy of Noosa.
                                                                     portion of the costs would likely be borne by
  This option is not considered feasible as the                      the broader community through general rates or
  analysis found there is a 60 per cent loss in                      other government funds, even though the works
  recreational benefits to users of the beach, a 14                  are expected to have negative impacts for the
  per cent loss in tourism expenditure and a 44 per                  community and economy given the loss of beach
  cent loss in non-use benefits (scenic amenity,                     values.
  landscape character) which is considered to
                                                                     It is important to note that the Eastern Beaches
  significantly outweigh the value of the private
                                                                     and Teewah Beach are unlike Noosa Main
  properties and public assets being protected.
                                                                     Beach, which has access to (and uses via the
  The construction of a physical barrier to withstand                sand recycling system) sand entering the river
  storm waves of the size that may potentially                       mouth as it moves northwards along the coast
  occur in these areas would also have a strong                      for replenishing the beach when it becomes
  potential to result in adverse impacts in adjacent                 eroded. This recycled sand is used to cover the
  locations as the erosive forces of wave energy are                 seawall along Noosa Main Beach. For the Eastern
  transferred to neighbouring properties that do not                 Beaches and Teewah, there is no readily available
  have a wall in place.                                              sand supply to continually recycle sand back onto
                                                                     the beach in front of a rock wall. As discussed in
  It is important to note that the analysis also did not
                                                                     the sand nourishment option, nourishment
  factor in the interruptions to beach use and



  26
       It is important to note that an ARI of 100 years does not mean that the event will only occur once every 100 years.
        While for each and every year, there is a 1% chance (a 1 in 100 chance) that the event will be equaled or exceeded,
        statistical theory shows that the chance of this event occurring or being exceeded over a longer period, say 50
        years, is around 40%. “That is, a 100 year ARI event has a high chance (40%, or between a 1 in 2 chance and a
        1 in 3 chance) of being equaled or exceeded over a 50 year period.” See Bureau of Meteorology (2021)’s online
        article: ‘Why do 100 year events happen so often?’, as well as Noosa Council’s Briefing Note titled: Natural Hazard
        Probabilities for more information.

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