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Other than direct property loss/damage through inundation, sea level rise creates many other issues that
need consideration that are separat from inundation. These include, amongst others, accelerated
degradation of materials (e.g. building foundations), fatigue due to extreme storm events and greater
wave energy penetration inland, increased corrosion, changes in groundwater composition as freshwater
aquifers are exposed to saline intrusion, and higher water tables putting pressure on subsurface
structures (pipes, tanks, pools, etc).
5.2.2. Storm surge
Figure 5.4: Illustration of how tides and elevated sea levels due to storms and climate change interact.
Source: Redrawn from McInnes et al. (2009)
Note: Elevated sea levels may contribute to flooding in low lying land near the coast as the result of water flowing back through
drains or because they impede drainage along storm water drains during any accompanying rainfall events.
Modelling by Tonkin Engineering and WBM Oceanics Australia (2005) for the Port Adelaide area
examined the effects of coastal flooding resulting from the 100 year average recurrence interval (ARI)
storm tide, projected sea level rise and land subsidence. It found that infrastructure damage in a 100
year ARI storm tide flood event would be approximately $27 million. This would increase to over $180
million in 2100 (accounting for sea level rise and subsidence, equivalent to an 88cm in flood elevations).
9
Tidal data is available for
Eastern
Gulf St Vincent from the
Outer Harbor
and Port Stanvac tide gauges.
Outer Harbor
tide
data is
considered to be representative of the coast throughout the Western Adelaide region.
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Highest Astronomic Tide (
HAT
) at Outer Harbor
is
1
.4 m
AHD
Lowest tide
Mean sea level
Highest tide
Wind waves
run up
Wave
set up
Storm surge
Sea level rise
Height of
storm tide
0 m elevation
(AHD)
The effects of storm surge conditions, which temporarily elevate sea levels significantly beyond their normal
tidal range (Figure 5.4) will be exacerbated by sea level rise. The 100 ARI (average recurrence interval)
water level at Outer Harbor at current mean sea level is 2.4m Australian Height Datum (AHD - approximate
mean sea level. At Outer Harbor, mean sea level is 0.13m below 0m AHD). These extreme water levels are
caused by storm surges coinciding with high tides. The impact of sea level rise can be estimated by adding
a selected sea level rise scenario to the current 100 year ARI water level.
