2021-10-08 SM - Item 1 - Attachment 1 - Draft Coastal Hazards Adaptation Plan

tides, and coastal erosion events due to rising sea levels. These events were modelled using
specialised software across four planning horizons – present day, 2040, 2070 and 2100.

Coastal hazard map layers produced as part of the development of this plan show potential
inundation and coastal erosion extents for each of these time steps. These map layers should not
be relied upon for making detailed design decisions as part of the development of buildings,
infrastructure or other structures at the individual lot scale. The mapping has been prepared to
identify areas of interest that require further investigation for mitigating potential risks.




What is coastal erosion?
Coastal erosion is the wearing away of land or the removal of beach or dunes by wave action, tidal
currents, drainage or high winds. Coastal erosion leads to the recession of shorelines inland and
the destabilisation of dune systems if the system is not able to rebuild before another erosive event
occurs.

Beaches in south-east Queensland typically consist of sand particles that can be easily eroded by
waves. These deposits comprise terrestrial sediment delivered to the coast by rivers, sediment
produced by the erosion of coastal landforms by waves, and marine sediment that has been
reworked from offshore deposits onto the coast.

Coastal erosion occurs when high winds, waves and tides combine to remove sand away from the
shoreline and dunes. This can be a short-term movement (called a ‘storm bite’), where the sand
gets pulled offshore and gradually returns the beach during calm conditions over many months.

Erosion sometimes occurs more gradually as water levels and currents change, causing the
shoreline to recede further inland relative to a previous position; this is called ‘shoreline recession’.
It can also occur when a hard structure is built within the active beach zone, and instead of
dissipating the wave energy like a sand dune would, it simply reflects that energy in-front (i.e.
seaward) of the structure, thereby preventing the sand to settle in that area and build up.

Figure 3 shows what happens during a storm event to the shore of the beach, as well as the likely
effect of significant increases in mean sea level. That is, as the local sea level increases so to does
the ocean’s ability to erode our sandy shorelines impacting the frontal dunes that form a protective
buffer between the force of the ocean and coastal development.




Noosa Council – Coastal Hazards Adaptation Plan                                                  Page 12