Storm surges
A Storm surge is an offshore rise in sea level as a result of the wind and atmospheric pressure changes associated with a storm. They have the ability to cause extensive flooding and damage to coastal areas.
What causes storm surges
Storm surges can happen during tropical storms like cyclones and hurricanes. The low pressure and high winds of tropical storms causes sea levels to rise and high waves and large amounts of water to rush ashore.
Intensive flooding of nearby coastal regions (coastal inundation) can occur during storm surges and low-lying areas can remain flooded for weeks after the storm has passed.
King Tides and storm surges
The magnitude of inundation and the extent of flooding that can happen during storm surges is intensified if the tropical storm hits during high tides. The risk is further escalated during especially high tides like Spring or King Tides. The topography and physical characteristics of coastal areas also determine if inundation will occur during storm surge.
How will I know if my area is at risk during a storm surge?
MetService is responsible for releasing weather warnings for New Zealand. They will issue a Severe Weather Warning whenever there is an expectation that a storm surge may arise.
NIWA also provides tide predictions for any location around New Zealand here.
How can I protect myself in the event of coastal inundation?
Strong winds, waves and coastal flooding caused by rising sea levels during storms and tidal events (coastal inundation) can cause substantial damage to public and private property and can cause breakdown of transport and communications. Coastal inundation also poses a threat to the safety of people in low-lying coastal areas.
If you find yourself in a situation of coastal inundation, the rules are simple: head for higher ground and stay away from the shoreline. Be careful as you make your way to safety, even a shallow depth of water has a surprising amount of force and uneven ground or dangerous objects may be concealed by the flood waters.
The likelihood and severity of coastal flooding during a storm is increased during high tide events such as Spring or King Tides. Because coastal inundation can happen relatively quickly and with little warning time, it is important to stay informed on the weather and be ready to act immediately.
MetService is responsible for releasing weather warnings in New Zealand and radio or television stations can be good sources of information for official weather and weather-related bulletins during a severe weather event.
To find out if you live in a coastal inundation-prone area contact Auckland Council on 09 301 0101. If you see inundation of houses and property please call 111. The Auckland Civil Defence and Emergency Management website has all the information you need to get ready for an emergency, and how to receive emergency alerts.
Climate change and storm surges
Rising sea levels, changing weather patterns and intensification of storms due to climate change will aggravate the existing coastal inundation problems experienced by some areas of New Zealand. The risk of inundation in areas that have been previously unaffected will also increase due to the effects of climate change.