As geographers, we classify the impacts of natural hazards into three main categories:
- Social
- Economic
- Environmental
Tropical Cyclones are dangerous because they produce destructive winds, heavy rainfall with flooding and damaging storm surges that can cause inundation of low-lying coastal areas.
Cyclones have wind gusts in excess of 90 km/h around their centres and, in the most severe cyclones, gusts can exceed 280 km/h. These very destructive winds can cause extensive property damage and turn airborne debris into potentially lethal missiles. It is important to remember that, during the passage of the cyclone centre or eye, there will be a temporary lull in the wind, but that this will soon be replaced by destructive winds from another direction.
Heavy rainfall associated with the passage of a tropical cyclone can produce extensive flooding. This can cause further damage and death by drowning. The heavy rain can persist as the cyclone moves inland and decays, hence flooding due to a decayed cyclone can occur a long way from the tropical coast as the remains of a cyclone move into central and southern parts of the continent.
The destructive winds accompanying tropical cyclones also produce phenomenal seas, which are dangerous both for vessels out at sea and those moored in harbours. These seas can also cause serious erosion of foreshores.
Potentially, the most destructive phenomenon associated with tropical cyclones that make landfall is the storm surge. Storm surge is a raised dome of water about 60 to 80 km across and typically about 2 to 5 m higher than the normal tide level. If the surge occurs at the same time as a high tide then the area inundated can be quite extensive, particularly along low-lying coastlines.
