Coastal Inundation

Coastal inundation is when sea water rises high enough that it floods infrastructure and buildings or endangers peoples' safety. 

The risk of coastal inundation is dependent on multiple factors, as well as the surrounding geography (e.g. if the town is on a hill or the beach). 

Fraser Coast residents who live near the coast should be aware of their potential risk.

Highest Astronomical Tide (HAT) – (Urangan 4.28m)

The highest level of water that can be predicted to occur under average meteorological conditions and any combination of astronomical conditions. This level may not be reached every year.

When a storm tide level is higher than the highest astronomical tide it is more likely to cause inundation and flooding in coastal areas.

King Tide

The term king tide has no scientific definition. In popular use, it refers to the highest tide that occurs at a location per year.

During normal weather conditions, the height of the king tides will be similar from year to year. In abnormal weather conditions (severe storms or tropical cyclones), the low air pressures and strong winds can elevate the sea level above the expected height.

Find out more about king tides or the highest tides for the year at the Maritime Safety Queensland website.

Storm Surge

An increase in water level associated with some a severe weather event such as:

  • persistent strong winds and storms
  • east coast low
  • tropical cyclone

Storm surges are the combined effect of wind setup and wave setup, and falling barometric pressure. In some situations, when winds blow offshore, sea level can fall lower than the predicted tide level too.

The magnitude of the storm surge depends on the severity and duration of the event and the seabed topography at the site. In Queensland, most large surges are caused by tropical cyclones.  

Storm Surge

Storm Tide

Storm tide is the water level that results from the combination of the storm surge and the normal (astronomical) tide. A 3 metre storm surge on top of a high tide that is 2 metres above the mean sea level will produce a storm tide that is 5 metres above mean sea level.

Storm tides can swamp low-lying areas, sometimes for kilometres inland. Strong winds at the coast can also create large waves, worsening the impact.

What can I do to prepare for coastal inundation?

Homes located within 100 to 200 metres of an open shoreline are at risk of impacts from breaking waves caused by storm tide.

Monitor Conditions

The following maps are indicative of possible evacuation zones for storm surge inundation.

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Disasters and Emergencies