2021-11-15 GC Agenda - Item 7 - Attachment 1 - Coastal Hazards Adaptation Plan

                                                                     Noosa Coastal Hazards Adaptation Plan



global greenhouse gas emissions pathway                      What is coastal erosion?
known as ‘RCP 8.5’, which is often referred to as
‘business as usual’ because up to now, human                 Coastal erosion is the wearing away of land or
emissions at the global scale have tracked this              the removal of beach or dunes by wave action,
pathway most closely12. This scenario results in             tidal currents, drainage or high winds. Coastal
a projected rise in regional mean sea level of               erosion leads to the recession of shorelines
approximately +0.8 meters by the year 210013.                inland and the destabilisation of dune systems if
The RCP 8.5 pathway represents minimal action                the system is not able to rebuild before another
being taken globally to reduce global greenhouse             erosive event occurs.
emissions14. The adoption of this scenario is a              Beaches in South-East Queensland typically
requirement of the QCoast2100 program15.                     consist of sand particles that can be easily eroded
Council acknowledges the value in considering                by waves. These deposits comprise terrestrial
a range of possible climate change scenarios as              sediment delivered to the coast by rivers, sediment
well as sources of local data in coastal hazard              produced by the erosion of coastal landforms
modelling and for these to be incorporated                   by waves, and marine sediment that has been
as part of future modelling reviews where                    reworked from offshore deposits onto the coast.
appropriate.                                                 Coastal erosion occurs when high winds, waves
Ongoing localised monitoring and data collection             and tides combine to remove sand away from the
are important inputs to managing coastal hazard              shoreline and dunes. This can be a short-term
risks, and are discussed further in Section 6 of             movement (called a ‘storm bite’), where the sand
this plan.                                                   gets pulled offshore and gradually returns the
                                                             beach during calm conditions over many months.
Noosa already experiences periodic tidal
inundation and coastal erosion events. The first             Erosion sometimes occurs more gradually as
stage of the project sought to understand how                water levels and currents change, causing
Noosa may be affected by changes in tidal water,             the shoreline to recede further inland relative
storm tides, and coastal erosion events due to               to a previous position; this is called ‘shoreline
rising sea levels. These events were modelled                recession’. It can also occur when a hard structure
using specialised software across four planning              is built within the active beach zone, and instead
horizons – present day, 2040, 2070 and 2100.                 of dissipating the wave energy like a sand dune
                                                             would, it simply reflects that energy in-front (i.e.
Coastal hazard map layers produced as part
                                                             seaward) of the structure, thereby preventing the
of the development of this plan show potential
                                                             sand to settle in that area and build up.
inundation and coastal erosion extents for
each of these time steps. These map layers                   Figure 3 shows what happens during a storm
should not be relied upon for making detailed                event to the shore of the beach, as well as the
design decisions as part of the development of               likely effect of significant increases in mean sea
buildings, infrastructure or other structures at             level. That is, as the local sea level increases so
the individual lot scale. The mapping has been               to does the ocean’s ability to erode our sandy
prepared to identify areas of interest that require          shorelines impacting the frontal dunes that form a
further investigation for mitigating potential               protective buffer between the force of the ocean
risks.                                                       and coastal development.


12
     or a simple explanation of Representative Concentration Pathway (RCP) 8.5 and other emissions pathways, see
    F
    Australian Academy of Science (2021): The risks to Australia of a 3oC warmer world. To understand how they are
    used in climate models, see Queensland Government’s description at https://www.longpaddock.qld.gov.au/qld-future-
    climate/understand-data/
13
   Intermediate projections for sea level rise are +0.2m by the year 2040, and +0.5m by the year 2070.
   It is important to note, RCP 8.5 presented in the IPCC’s Fifth Assessment Report (AR5) roughly corresponds to the
14 

   new Shared Socioeconomic Pathway (SSP) 5-8.5 in the latest IPCC (2021) Sixth Assessment Report (AR6).
15
    For more information, see Noosa Council’s Briefing Note titled: Use of sea level rise projections
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