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Coastal inundation for the whole Study Area and existing sediment modelling may need to be revised
following the release of climate change from the IPCC’s Fifth Assessment Report (results due from 2013).
5.2.
Coastal climate change
5.2.1. Sea level rise
Global mean sea levels are projected to rise by between 18 and 59 cm by 2100 (CSIRO and BoM, 2007),
not accounting for the contribution of ice sheet melt. More recent research points to more rapid sea level
rise, in part due to the loss of ice from the Greenland and some Antarctic ice sheets. Ramstorf (2006)
projects sea level rises of between 0.5 to 1.4 m by 2100. The IPCC (2007) projected a rise of 0.82 m by
2100 under the high emissions A1FI scenario, accounting for thermal expansion of oceans and ice sheet
melt and 0.15 m for 2030 and 0.47 m for 2070.
Sea level changes have been measured in the region. Tide gauges record sea level rises of 2.06mm/y
(until 1997) and 2.08 mm/y for the Inner Harbour and the Outer Harbour, respectively
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.
Several sea level modelling exercises have been undertaken across the Adelaide region, using both one
dimensional and two dimensional models. The former indicate areas that are potentially exposed to
coastal flooding on the basis of surface elevation. They do not consider whether it is possible for elevated
sea waters to actually reach a low-lying location. Tonkin Engineering and WBM Oceanics (2005)
prepared a full two-dimensional hydrodynamic model for parts of the Study Area. This study considered
both the elevation of land and the potential for water to reach it (as influenced by topographic controls
provided by infrastructure such as roads). It provides a more reliable indication of exposure to coastal
flooding in response to climate change than studies (e.g. OzCoasts, 2012) that use only one dimensional
projections.
Three scenarios have been modelled by OzCoasts (2012) to identify locations in the Study Area that may
be exposed to coastal flooding that would result from the combination of the highest astronomical tide
(HAT) and sea level rise.
Figure 5.1 (a-e)
= 50 cm sea level rise;
Figure 5.2 (a-e)
= 80 cm sea level rise; and
Figure 5.3 (a-e)
=
110 cm sea level rise. It does not account for the influence of storm surges (above the HAT) on elevated
water levels or any impacts of impeded surface water drainage.
While the underpinning analysis has not accounted for any protection from flooding that may be offered
by roads, sea walls, levees and other infrastructure, it highlights that the Study Area includes significant
areas of very low-lying land. Residential and other buildings in these areas could be exposed to periodic
coastal flooding events as a result of sea level rise unless protective infrastructure was developed.
Land subsidence in the Study Area has potential to exacerbate the impacts of projected sea level rise.
The historical average rate of subsidence in the Port Adelaide area is 1.8 mm/y.
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Department for Environment and Heritage (2005) Adelaide’s Living Beaches” A strategy for 2005- 2015, Technical Report
