Despite the presence of the Great Barrier Reef, the Cairns region can still be affected by a tsunami. Although the reef may reduce the impact of a tsunami, the scale of impact depends on what caused the tsunami, how far away the event is and where it is in relation to Cairns.
The effects of tsunamis originating in locations from Chile to Tonga have been recorded in Queensland since 1868 - the Cairns disaster management unit regularly receives information about undersea earthquakes and tsunamis around the world. Although we do not live in a high risk area, a tsunami could also be triggered on the edge of the Great Barrier Reef. We may have only a few hours’ warning.
Even a relatively small tsunami of a metre in height or less can move with force and cause dangerous rips and currents.
What is a tsunami?
Tsunamis are a series of long ocean waves or surges, caused by a major disturbance to the sea floor such as an undersea earthquake, landslide or volcanic eruption. They are different to the storm tide surge which can occur with cyclones and from large waves which can accompany storms.
Tsunamis achieve speeds comparable to those of airliners and may travel for hundreds of kilometres, hitting distant communities hours after they are generated. They slow down but grow in size as they come ashore. Rather than one huge wave, a tsunami may look like a rapidly rising or falling tide and occur as a series of waves with periods of time in between.
What will happen?
Tsunamis can happen any time of year. Warning information will be issued by local emergency authorities on the advice of the Bureau of Meteorology.
- If a tsunami threat is likely, information will be broadcast on all available public media such as radio, TV, web sites and social media.
- It may also be provided by emergency services in areas likely to be affected, eg through loud hailers or door knocking.
- You may receive emergency alerts through mobile and landline phones and hear the SEWS (Standard Emergency Warning Signal).
- If you’re at the beach or can see the ocean, you may notice changes such as the water withdrawing, or suddenly becoming shallow, or unusual or unexpected waves approaching.
- A tsunami may not be one large wave approaching the coast. It can occur as a series of seemingly quite low but very powerful waves. The force of the water may be so strong it can carry vehicles, boats, bridges and buildings with it.
What should I do?
- Move quickly from low lying areas to higher ground- in many situations this is just a few streets away and it will be easiest to walk.
- If you are at home and need to drive to leave, take your household emergency kit. Otherwise put emergency supplies such as a battery operated radio and torch, medications, water, snacks and cash in a bag you can walk with.
- Don’t stay to watch the tsunami!
- Head for your nearest area of higher ground (eg Smithfield, Mt Sheridan). You can use the Cairns region storm tide surge maps for guidance on reaching higher ground. Do not go to Copperlode Dam or the Tablelands.
- Get out of the water and away from the coast.
- Follow local instructions and take immediate action, no matter how small the tsunami may sound.
- Stay where you are if your location is on high ground.
View your evacuation route:
After a tsunami
- Keep listening and be alert for instructions from local emergency authorities.
- Stay in your high ground location until advised it is safe to leave. More waves are likely to follow the first and it may take time for this to happen.
- Keep out of flooded areas even if you know them well, as hazards below the water may not be apparent. Floodwaters may also be contaminated by sewage and other pollutants.
- Follow the advice provided by local emergency authorities. Call for help if you need it.