2021-10-08 SM - Item 1 - Attachment 2 - Draft Coastal Hazards Adaptation Plan - 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 energy erosive forces are transferred to neighbouring properties that do not
have a wall in place.

The analysis also noted that the analysis did not factor in the likely interruptions to beach use and
adverse effects for adjacent properties during construction which may increase the costs of this
option. In addition, there remains uncertainty regarding material costs and construction costs, and
material supply in term 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 a 100
year ARI storm event. The required height, required length, land tenure arrangements (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,
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 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 at this stage for any of the localities.


Fact sheets about the adaptation options subject to a cost-benefit analysis, including those
described above, can be found on the project page on Your Say Noosa.


Options for responding to coastal inundation risks
Water levels in the lower Noosa River and its tributaries (including the lakes) can become elevated
due to a number of factors including rainfall across the catchment area, a storm tide, or during
sunny days as a result of higher-than-average tides. The area of land subject to the effects of
storm tides is expected to increase as a result of sea level rise. In addition, the reach of tidal
Noosa Council – Coastal Hazards Adaptation Plan 2020 - 2030                                    Page 30