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

Executive Summary

Climate change is leading to sea-level rise and an increase in the frequency of coastal erosion events
relative to the present day. Coastal erosion and shoreline recession pose a significant risk to the
social, economic and environmental values present along Noosa Shire Council’s (Council) coastline.
Typical options available to maintain these values include seawalls, revegetation, and beach
nourishment, as well as early warning disaster systems and land use planning.

Aither was engaged by Council to undertake a socio-economic analysis of potential adaptation
options at two locations; Eastern Beaches which includes Peregian, Marcus, Castaways, Sunrise and
Sunshine Beach suburbs, and Teewah. At this stage of investigation, the socio-economic analysis
aims to:

•    support Council’s understanding of the merit of different options

•    assist Council to communicate the benefits and costs of options to stakeholders

•    determine if more detailed investigation is required.

The socio-economic analysis investigated the effects of coastal erosion between 2020 and 2100. In
accordance with modelling completed by BMT (BMT, 2020), coastal erosion moves progressively
landwards at the Eastern Beaches and Teewah, as sea levels rise. The risk to assets at these
locations progressively increases if no management activities are undertaken, with the scale and
speed of increases differing across the coastline due to factors specific to each location. Aither’s
analysis assessed the following adaptation options:

•    Option 1 (Base case): no adaptation actions undertaken

•    Option 2: Dune revegetation and management

•    Option 3: Dune revegetation, augmentation and management

•    Option 4: Construction of seawalls in high risk locations

•    Option 5: Acquisition of all properties followed by rezoning of land to public open space that
     supports natural coastal processes

•    Option 6: Option 5 with a 15-year leaseback of properties prior to conversion to public open
     spaces

•    Option 7: Changes to planning provisions to prevent development within the projected 2070
     coastal erosion prone area.

The analysis demonstrates that option 3 provides the greatest economic net present benefit for
managing erosion risks along the Eastern Beaches (Table E1). The benefits of this option are driven
by the significant value provided by the continued natural protection of high value beachfront
properties. Investigation into the full costs and risks of undertaking option 3 should therefore be a
priority for Noosa Council.

Option 7 also delivers net economic benefits, although the net benefits are lower than under option 3.
Implementing planning restrictions such as those in option 7, alongside dune augmentation in viable
locations is likely to deliver socio-economic benefits to the community and reduce risks. Further
investigation into the full costs of dune augmentation and detailed land use planning provisions should
therefore be undertaken.




AITHER | Final Report                                                                                   3
Noosa Shire Council – Coastal Hazard Adaptation Plan