2021-01-18 GC - Item 3 - Attachment 3 - Cost Benefit Analysis for Coastal Erosion Options

5.           Results and findings

5.1.         Results
The CBA results are provided for Eastern Beaches and Teewah in the following tables:

•     Table 3 provides headline net present value results for each option at the Eastern Beaches and
      Teewah locations. The results show the net present value of the benefits today, accounting for all
      benefits and costs over the period 2020-2100.

•     Table 4 and Table 5 provide the costs of each option relative to the base case which
      demonstrates which project options are preferable from an economic perspective.

Results are provided in present value terms, with an assumed real discount rate of 2.3 per cent. The
discount rate is based on Council’s cost of borrowing. This assumption has been tested through the
sensitivity analysis (Appendix C).

Table 3        Summary results – NPV, discount rate of 2.3%, present values calculated for the
               period 2020-2100

                    Options
    Location        Option 2            Option 3       Option 4   Option 5   Option 6        Option 7
    Eastern         $63m                $239m          -$2773m    -$222m     -$70m           $73m
    Beaches
    NPV
    Teewah          $0.3m               -$17m          -$67m      $16m       $9m             n/a
    NPV



5.1.1.       Option 2 - Dune revegetation and management

Under option 2 dune revegetation and management is undertaken every 5 years until 2100. In
locations where erosion is not already too far advanced dune management can help to delay damage
to properties and assets. Advice from BMT notes that in some areas dune management can help
delay damage to 12 properties for 30 years.

Under this option there is a positive NPV of $63m at the Eastern Beaches and $0.3m at Teewah.
However, it should be noted that the positive NPV is associated with very low costs of action, rather
than the delivery of significant benefits. For example, there is only a 7 per cent increase in property
benefits over the baseline. Dune management is a low cost, low risk management option which does
provide benefits from delaying damage to properties and assets. It can also delay erosion so other,
more substantive, options can be investigated. Given the high value of these properties and the low
costs, dune management could be considered a ‘no regrets’ action and thus worth undertaking in the
short term.


5.1.2.       Option 3 - Dune revegetation, augmentation and management

Option 3 includes both dune management and revegetation and dune augmentation. Dune
augmentation requires a supply of additional sand to be added to the beach, with the use of
earthmoving equipment to shape the beach and dunes.


AITHER | Final Report                                                                                   16
Noosa Shire Council – Coastal Hazard Adaptation Plan