Natural Hazards

Beach erosion

Coastal erosion and flooding occurs in the Auckland region, and can cause significant problems if people build too close to the coast. Beaches move constantly, and naturally oscillate between periods of erosion and accretion (onshore collection of beach sediment). Sometimes these fluctuations reach extremes. Extreme fluctuations are only ever a problem when humans develop buildings or infrastructure too close to the coast. Coastal hazards occur when dynamic coastal movements interact with static human resources that we have placed along the coast. Two of the most common coastal hazards in the Auckland region are:

• coastal erosion
• coastal flooding

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Biological hazards

There are a large range of biological hazards that if not controlled or avoided, could cause significant loss of life or severely affect New Zealand's economy, agricultural and fishery industries, health (human & animal), and infrastructure (e.g. water supply and treatment networks). Due to our economic dependence on horticultural, agricultural and forestry industries, and limited historical exposure to disease, New Zealand is very susceptible to biological hazards.

A pandemic can also be a man-made hazard. Click here for more information on man-made pandemics.

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Coastal cliff erosion

Cliff failure can occur in a number of ways from slumping to large block failures. The coastal cliffs in Auckland are slowly eroding. Cliffs on Auckland’s East Coast are most susceptible, eroding at a rate of approximately 2-6m per century. This has been the case for the past 6-10,000 years.

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Climate change

Climate is changing. Future changes in temperature, precipitation, and other climate variables will alter Auckland's soil moisture and mean sea level. Some locations will be more susceptible to floods and droughts.

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Cyclones

Five tropical cyclones have passed within 220km of Auckland City between 1970 and 2001.

The main hazards associated with tropical cyclones are wind gusts and heavy rainfall, but they can also generate significant storm surge and coastal erosion.

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Drought

Drought occurs due to a deficiency of precipitation over an extended period of time, usually a season or more. Drought can be defined in various ways. An 'agricultural drought' is a period when the soil is estimated to be 'moisture deficit'. A significant agricultural drought can impact on Auckland's agricultural and horticultural industries. A 'hydrological drought' is when the effects of low precipitation affect hydrological systems. A hydrological drought can result in a water supply shortage, although storage capacity and demand are also important factors.

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Earthquakes

Although the Auckland region lies in one of the lowest earthquake activity regions of New Zealand, earthquakes of varying magnitude are likely to occur at some stage in the future. The extent of this damage will depend on the ground conditions of a particular site, building and infrastructure condition, response and recovery plans, and the community awareness of what to do.

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Fire

Urban Fire
Every year Auckland has between 5000-6000 urban fires that require response from emergency services, and cause 10-15 fatalities. These are predominantly from house and industrial fires.

Wildfire
In the Auckland region there is a small risk of wildfire in the forested areas to the west (Waitakere Ranges), south (Hunua Ranges), northwest (Woodhill Forest), north (Mahurangi Forest) and east (Gulf Islands).
Fires in these areas can result from agricultural burn-off getting out of control, arson, careless actions (e.g. camp fires in restricted areas), or natural causes such as lightning strikes. Weather plays a significant factor - the risk of fire increases in prolonged drought conditions.

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Flooding

In the Auckland region, most flooding events are of short duration and affect relatively localised areas.

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Hazards from outside Auckland

Hazards that occur in regions outside of Auckland can also affect people and communities in Auckland.

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Land instability

Erosion and slope failure is common throughout the Auckland region. Land instability is often made worse by human activities.

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Tornado

Tornados frequently occur in Auckland but Auckland’s tornados are much smaller than the very large ones that occur in the midwest of the United States.

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Tsunami

Tsunami may be tens of metres in height in shallow water, however most tsunami are less than 1m in height at the shore. Historical information suggests that the most likely hazardous tsunami event for the Auckland region is likely to be caused by an earthquake off the west coast of Chile.

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Volcanic hazards

Much of Auckland is built on a potentially active volcanic field. Within an area of about 360 square kilometres, there are approximately 50 volcanoes. None of these existing volcanoes are expected to erupt again. The next eruption will be in a new, unknown location.

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