Storm Surge is a raised dome of sea water, some 50 or more kilometres across, and up to several metres in height, above normal sea level, at its peak. It is a massive movement of sea water and its effect of raising the sea above the level of the normal tidal movement can last for several hours. Storm surge occurs when a tropical cyclone moves across or near the coast. A storm surge is not the same as a tidal wave (tsunami). A storm surge comes in like a rapidly rising tide and can be extremely dangerous and destructive. The height of the storm surge will depend on the following:
Winds rotate clockwise in tropical cyclones in the Southern Hemisphere and the storm surge is highest on the left hand side (looking at the direction of motion) of the system. Therefore a tropical cyclone crossing the coast to the north of Cairns will produce a greater storm surge than those crossing to the south of Cairns Storm Tide The combination of storm surge and normal (astronomical) tide is known as STORM TIDE. The worst impacts occur when the storm surge arrives on top of a high tide. When this happens the storm tide can reach areas that might otherwise have been safe.
Storm Surge/Tide Inundation Storm surge/tide inundation occurs when the total water level moves overland. Inundation includes breaching dunes or coastal protection structures and over bank flows from water courses and/or storm water drains. Inundation effects of storm surge are intensified by wave overtopping and localised intense rainfall which can cause coincident freshwater flooding. Breaking waves and wave 'run-up' can also contribute to the storm surge/tide level and the overall hazard at exposed coastal locations Loss of life, damage to infrastructure and beach erosion, including loss of private property, can be caused by wave action and extreme water levels associated with these severe inundation events. |
In a Tropical Cyclone Event, ALWAYS act on official advice provided by Local Authorities and Emergency Managers
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