Stor m Surge: Know your risk in Queensland!
Storm surge is a rise in sea level above the normal tide usually associated with a low pressure
weather system such as a tropical cyclone. Storm surge develops due to strong winds
pushing water towards the coastline as well as the low atmospheric pressure drawing up the
sea surface.
The Queensland coastline is highly vulnerable to storm surge. This is due to the frequency of tropical cyclones, the wide
continental shelf and relatively shallow ocean floor in both the Great Barrier Reef lagoon and in the Gulf of Carpentaria,
as well as the low lying nature of many coastal cities and towns.
While the highest storm surges are more likely to occur in North Queensland and the Gulf of Carpentaria, they can also
develop in southeast Queensland affecting the Sunshine Coast, Moreton Bay and the Gold Coast. Storm surges may
reach magnitudes of 1 to 10 metres above the tide depending on the intensity of the cyclone, its size and the local
characteristics of the coastline.
Impacts
Coral Sea
Storm surge can be very dangerous and poses a critical risk
to human life during tropical cyclones.
Gulf of
Carpentaria
Cairns
Innisfail
Cardwell
The length of coastline affected by a storm surge can be
tens to hundreds of kilometres wide. The rise in sea level
can be rapid and high in velocity, inundating the ground
floor of buildings, even up to the roof.
Storm surge has the power to easily move cars, even
houses, can damage roads and buildings and can be
almost impossible to manoeuvre through. Additionally, the
storm surge can carry dangerous debris, which can cause
structural damage to buildings and pose a high risk to life.
Great
Barrier
Reef
Townsville
Bowen
Mackay
Queensland
Hervey Bay
Sunshine Coast
N
0
Gladstone
Brisbane (Moreton Bay)
200km
Gold Coast
This information booklet was prepared by Griffith Centre for Coastal Management to educate Queensland’s coastal communities
about storm surge.
Storm surge destruction from Tropical Cyclone Yasi (February 2011), Tully Heads, Qld
(Source: Marc McCormack, News Limited).
Total Water Level
The total water level experienced on land during a cyclone
is made up of contributions from the storm surge, tide,
freshwater flooding and wave run-up.
Total Water Level = Storm Surge + Tide +
Freshwater Flooding + Wave Run-up
What is a storm tide?
Storm tide is the water level resulting from the
combination of the storm surge with the astronomical
tide, and is referred to a vertical datum such as Lowest
Astronomical Tide, Highest Astronomical Tide or
Australian Height Datum, AHD (equivalent to Mean Sea
Level at major ports).
Budds Beach during ex-TC Oswald, Gold Coast, 28th January 2013
(Source: GCCM, 2013)
Flooding
Storm surge can travel many kilometres inland and rising
waters may come from estuarine waterways as well as
the open coast. Low lying areas surrounding estuaries
are vulnerable to the combination of storm surge and
upstream flooding from heavy rainfall. Properties on the
beachfront are also at risk from sea water inundation
due to storm surge as well as wind-induced waves.
Storm Tides
The impact of a storm surge is highly dependent on
the phase of the tide and the surge will have greater
impact if it arrives during a high tide. This may result
in extremely high water levels. When forecasting the
cyclone, the timing of cyclone landfall is uncertain,
making it difficult to predict an exact water level. The
peak of the storm surge may occur prior to or after the
cyclone making landfall. It can also occur without the
cyclone crossing the coast.
High tide
Mean sea level
Low tide
A. Normal tidal conditions
Storm tide
Storm surge - measured from
High tide
height of the tide at the time the
cyclone crosses the coast.
Mean sea level
Low tide
B. Cyclone conditions
A. Water level during normal conditions. B. Conditions during
a cyclone showing elevated sea level due to storm tide.
Waves
Storm surge is usually accompanied by extreme ocean
waves created by hazardous winds during the cyclone
event. These add to the total water level through wave
run-up.
Wave run-up is the maximum height of the waves rushing
up on the beach. This is due to both wave set-up as well
as the swash of broken waves on the shoreline.
Wave set-up is the elevation of sea level above the storm
tide level as a result of water piling up against the shoreline
due to the momentum of the breaking waves.
These conditions can lead to beach erosion and add
further impact to beach front properties.
Storm surge flows through bottom storey of house at
Tully Heads during TC Yasi, 2011 (Source: JCU, 2011)
Atmospheric pressure increasing
Tropical Cyclones
Low pressure
A tropical cyclone is a violent storm characterised by
a calm low pressure eye surrounded by strong winds
Cyclone
Onshore winds
Storm surge is
eye
rotating clockwise in the Southern Hemisphere.
Wind set-up
amplified in shallow water
They form over tropical waters of temperatures
Pressure induced
rise in sea level
greater than 26.5°C and can persist over oceans
with lower temperatures, although the energy tends
to dissipate over cooler waters and land. A cyclone’s
Cross section of a cyclone showing the storm surge due to both the wind setintensity is categorised based on the severity of its
up and pressure induced rise in sea level.
wind (see below).
Forecasting
Every cyclone is unique in its behaviour resulting in a
high level of uncertainty when it comes to forecasting
where and when they will cross the coast. A cyclone
can travel for hundreds of kilometres, may move
erratically, even making sharp turns or loops, and
change intensity rapidly. In Queensland, a cyclone may
form in the Coral Sea and cross Cape York into the
Gulf of Carpentaria or vice versa, and can track parallel
to the coastline either north or south.
The Australian cyclone season extends from
November through to April with an average of 10
cyclones per year, although not all make landfall.
Tropical Cyclone Yasi making landfall in February 2011
(Source: www.bom.gov.au).
Tropical Cyclone Categories
Cyclone
Category
Sustained Wind
Speeds (km/hr)
Wind Gusts
(km/hr)
Typical Damage
1. Tropical cyclone
62-88
90-125
Negligible house damage; damage to crops, trees and caravans.
2. Tropical cyclone
89-117
125-164
Minor house damage; significant damage to crops, trees and signs.
3. Severe tropical cyclone
118+
165-224
Roof and structural damage; power failure likely
4. Severe tropical cyclone
118+
225-279
Significant roof loss and structural damage; widespread power failure;
dangerous airborne debris
5. Severe tropical cyclone
118+
280+
Extremely dangerous with widespread destruction
Source: www.bom.gov.au/cyclone/about/intensity
Most severe cyclones in Queensland
1. Tropical Cyclone Monica (2006) was the highest
intensity cyclone on record to impact the east coast of
Australia, making landfall as a Category 5 system close
to Lockhart River in Far North Queensland. The storm
surge magnitude for this event is unknown given the
remote nature of the impact area.
2. Tropical Cyclone ‘Mahina’, occurring in 1899, caused
the largest death toll of any natural disaster in Australian
history. Over 400 people were killed on shipwrecks in
Bathhurst Bay in Far North Queensland due to extreme
waves and storm surge.
Nott et al., 2013 The world record storm surge and the most intense
southern hemisphere tropical cyclone - new evidence and modelling.
Bulletin of the American Meteorological Society.
Tropical Cyclone Monica’s track across Queensland and the
Northern Territory in April 2006 (Source: Bureau of Meteorology).
Recent Storm Surge Events in Queensland
Tropical Cyclone Yasi
In 2011, Severe Tropical Cyclone
Yasi made landfall over South
Mission Beach as a marginal
Category 5 system with maximum
wind gusts of 285 km/hr. It
produced a storm surge peaking
at 5.3 m at the town of Cardwell.
TC Yasi made landfall at close to
low tide, and the storm tide was
4.5 m relative to mean sea level
(AHD). If TC Yasi crossed the coast
at high tide, the storm tide could
have reached over 7 m AHD.
TC Yasi was a large cyclone and
storm surge over 1 m affected
the Queensland coast from Port
Douglas to Bowen.
Waves over 9 m high were
recorded in Townsville.
In the towns of Tully Heads,
Hull Heads, Cardwell and Port
Hinchinbrook, houses were
inundated and in some cases
completely destroyed or washed
away. Robust evacuation
strategies meant that no fatalities
occurred.
Tropical Cyclone Larry
Tropical Cyclone Larry made
landfall over Innisfail in North
Queensland in 2006 and was
a Category 5 system prior to
landfall. While Larry was classed
as a ‘midget’ cyclone with a
small radius of just 30 km, it
was associated with strong wind
speeds and storm surge peaking at
2.3 m at Clump Point. Inundation
along the coastline was higher
that this level, generally around
3.5 m, reaching up to 5.2 m AHD.
This was due to a combination of
wave set-up, onshore wind forcing
and local coastal bathymetric (sea
floor) and topographic effects.
Damage to external shed wall by storm surge at
Tully Heads during TC Yasi (Source: JCU, 2011).
Tropical Cyclone Oswald
Tropical Cyclone Oswald developed
in the Gulf of Carpentaria in
January 2013 and tracked as an
ex-tropical cyclone down much
of the east coast of Queensland.
This brought gale force winds,
high swell, intense rainfall and
some storm surge. The persistent
northerly wind direction caused
storm surge of over 1 m in
southern Moreton Bay. While
the storm surge alone did not
cause appreciable flooding on
the open coast, when combined
with flooded estuaries and high
waves, it contributed to inundation
in small urban catchments and
significant beach erosion along the
Sunshine Coast and Gold Coast
beaches.
Damage to building at Clump Point during TC
Larry (Source: EHP, 2007)
Storm surge and high tide covering a boat ramp
at Biggera Creek, Gold Coast, during ex-TC
Oswald (Source: GCCM, 2013).
Sea foam and an uprooted tree at Burleigh
Beach, Gold Coast, during ex-TC Oswald
(Source: GCCM 2013).
Be aware of your storm tide risk and be prepared to evacuate when directed.
For more information
Bureau of Meteorology
www.bom.gov.au/cyclone/about
Queensland Fire and Emergency Services
www.emergency.qld.gov.au/emq/css/cyclone.asp
www.emergency.qld.gov.au/emq/css/storm_surge.asp
Department of Environment and Heritage Protection
www.ehp.qld.gov.au/coastal/development/assessment/coastal_hazards__storm_tide_inundation.html
www.ehp.qldgov.au/coastal/monitoring/storm-tides/index.php
See your local Government website for local details regarding storm surge.