2021-01-18 GC - Item 3 - Attachment 4 - Cost Benefit Analysis for Noosaville Inundation Options

in the Noosaville area by tidal waters, maintenance of the stormwater network will need to occur on a
more regular basis to overcome the damage caused by frequent inundation.

Under the proposed adaptation options the frequency of inundation by tidal waters is reduced,
thereby reducing the damage to stormwater assets and mitigating the costs of maintenance for
council. Assumptions on the expected maintenance costs and the different lifespan of the stormwater
assets under different levels of inundation have been provided by Noosa Shire Council and are
provided in Appendix A.

Avoided property damage
Although the inundation caused by sea level rise is not expected to be of a depth or velocity to cause
significant property damage in the region, there may be minor damages caused by increased salinity
from frequent inundation or saline groundwater intrusion. Under the base case properties close to the
river, creeks and lake are potentially affected by low-level inundation which may lead to increased
maintenance costs for property owners (for example of gardens and driveways).

A report on dryland and urban salinity costs across the Murray-Darling Basin (S Wilson, 2004) provides
expected yearly property repair costs due to increased salinity. Whilst these are driven by dryland and
urban salinity impacts there is limited data on the impacts of coastal salinity damage. These costs have
been used to approximate the potential damage costs to residential properties and tourist
accommodation in relevant areas, however these costs are low confidence, and should therefore be
investigated further.

Under the project options the extent of inundation is reduced thereby mitigating the expected
property damage caused in comparison to the base case.

Recreational and amenity benefits
Publicly accessible open space provides amenity benefits to the local community. Amenity benefits
can include both tangible benefits such as recreation, or non-tangible benefits such as aesthetic
appreciation. These open spaces in Noosaville, in particular those along the river foreshore, are at
greater risk of being affected by the increased inundation as a result of sea level rise. Under the base
case the local community is restricted from accessing these areas whilst they are inundated, and
therefore the amenity value of these assets is reduced. There are also likely to be additional costs
associated with maintaining and restoring recreational areas affected by inundation, however due to
limited information available these costs have not been included at this stage of the analysis.

Under the project options the extent of recreational areas inundated is reduced and the recreational
and amenity benefits associated with access to these public open spaces are therefore greater
compared to the base case.

These benefits have been quantified based on average yearly household willingness to pay for public
open space (Ambrey and Fleming, 2014), and the amount of additional time these spaces are
accessible.

Tourism benefits
Tourism is a key benefit to the region. It is assumed that low-level inundation, especially of areas
along the foreshore and other popular visitor locations, will have a negative effect on the number of
visitors to the Noosaville area. The reduction in visitation is assumed based on the amount of time
that key areas of Noosaville are expected to be inundated each year.




REPORT | Noosa Shire Council CHAP – Phase 7                                                                6