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Friday, January 14, 2011

STORM TIDES

storm tides

Coastal communities are at risk

Historical settlement patterns have resulted in Australia having most of its major city developments situated on the coastline. Storm tides are a major natural hazard for coastal regions. Severe storms and cyclones contribute 29 per cent of the total damage cost from natural hazards to the Australian community. In 1999 prices, this amounts to $40 billion during the period 1967 to 1999 (including the cost of deaths and injuries).



Storm tides pose many risks

A storm surge is an increase in coastal water levels well above the normal high tide. If the storm surge is combined with daily tidal variation, the combined water level is called the storm tide. When the resulting storm tide exceeds the normal tidal range, local beach topography will dictate whether significant coastal inundation will occur. Flooding by sea water in low lying coastal regions for periods of several hours and over as much as 100 kilometres of coastline can take place, placing property and lives at risk, affecting business activity and the financial security of a region. Evacuation of low-lying areas prior to a storm landfall is required in some circumstances to help prevent loss of life through drowning. Wave action, elevated water levels and surge run-up also attack dunes and near-shore structures to cause considerable erosion, as demonstrated in Figure 1.



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