2021-11-15 GC Agenda - Item 7 - Attachment 2 - Coastal Hazards Adaptation Plan with tracked changes

The construction of a physical barrier to withstand storm waves of the size that may potentially
occur in these areas would also have a strong potential to result in adverse impacts in adjacent
locations as wave energythe erosive forces of wave energy are transferred to neighbouring
properties that do not have a wall in place.

The analysis also notedIt is important to note that the analysis also did not factor in the
interruptions to beach use and potential adverse effects for adjacent properties during construction,
which may increase the costs of this option even further. In addition, there remains uncertainty
regarding material costs and construction costs, and material supply in termterms of access to
feasible rock supply.

Even without these broader socio-economic costs, the financial cost of implementation would be
significant, given the level of protection required to withstand a major storm event such as aone
with an average recurrence interval (ARI) of 100 year ARI storm event.years (i.e. occurs on the
average once in every 100 years)26. The required height, required length, land tenure
arrangements (e.g. where should it be located, who would maintain it), would lead to excessive
construction and ongoing maintenance costs.

Depending on the funding arrangements, a portion of the costs would likely be borne by the
broader community through general rates or other government funds, even though the works are
expected to have negative impacts for the community and economy given the loss of beach
values.

It is important to note that the Eastern Beaches and Teewah Beach are unlike Noosa Main Beach,
which has access to (and uses via the sand recycling system) sand entering the river mouth as it
moves northwards along the coast for replenishing the beach when it becomes eroded. This
recycled sand is used to cover the seawall along Noosa Main Beach. For the Eastern Beaches and
Teewah, there is no readily available sand supply to continually recycle sand back onto the beach
in front of a rock wall. As discussed in the sand nourishment option, and nourishment of the area
between Peregian and Sunshine Beach would provide a net benefit, however, its effectiveness is
not expected to continue beyond the year 2070. In addition, there are material uncertainties
regarding a reliable long-term sand supply in the nearshore and offshore environment (i.e. adjacent
to these localities). The analysis undertaken for the sand nourishment option assumed this
sediment would remain available until the end of the planning period (2100).

The analysis demonstrates that the construction of hard-engineered revetment walls would be
unviable as it is unable to demonstrate sufficient public benefit to justify the economic, social and
environmental costs involved. This option is therefore considered not feasible from a socio-
economic perspective.

Acquisition of private residential properties (option
(Option is deemed not feasible)

This option looked at what opportunities could be available for Council to acquire properties
impacted by coastal erosion. This also included options for temporary lease back to the property
owners. The cost benefit analysis demonstrated that this option does not deliver sufficient benefits
and therefore is not feasible for further consideration for any of the localities.


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.
Noosa Council – Coastal Hazards Adaptation Plan                                                       Page 39