Beach erosion and flooding
Coastal erosion and flooding occurs in the Bay of Plenty, 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. Read more...
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 and 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.
Cliff erosion
Cliff failure can occur in a number of ways from slumping to large block failures.
Climate change
Climate is changing. Future changes in temperature, precipitation, and other climate variables will alter Bay of Plenty's soil moisture and mean sea level. Some locations will be more susceptible to floods and droughts.
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Severe Weather
By virtue of its mid-ocean geographical position between the sub-tropical and mid-latitude belts, and its land-mass structure, New Zealand is vulnerable to a range of climate conditions with potential to create severe weather hazards.
The major effects of severe weather over the Bay of Plenty include:
- Rainfall (affecting all or any part of the region)
- High Winds (affecting all or any part of the region)
- Storm Surge and Storm Tides (affecting coastal areas)
Drought
Drought occurs due to a deficiency of rain 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 Bay of Plenty’s agricultural and horticultural industries. A 'hydrological drought' is when the effects of low rainfall affect hydrological systems. A hydrological drought can result in a water supply shortage, although storage capacity and demand are also important factors.
Earthquakes
The Bay of Plenty is one of the most seismically active areas of New Zealand. Earthquake activity is greatest in the central part of the region, within the area encompassed by the Taupo Volcanic Zone and the North Island Shear Belt, the latter being a zone of faulting which runs down the spine of the North Island from Whakatane southwards. Seismic hazard in this area, which encompasses Whakatane District and part of Rotorua District, may be significantly higher than previously estimated.
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Fire
Although 20.1% of the Bay of Plenty is covered in production forests with indigenous forests covering another 47.3%, the risk of a major fire event that would require the declaration of a local state of emergency is considered to be low. However the potential exists for a declaration to be needed where residential areas are located adjacent to forest areas. The impact of a large exotic forest fire would be devastating for local industry based economies dependant on tree harvest and log export. It is likely that current and future planned management mechanisms would restrict any outbreak and it would certainly be unlikely to develop into an event warranting a local state of emergency.
Flooding
Vulnerability to flooding varies throughout the region. The greatest threat exists to Opotiki and settlements on the Rangitaiki Plains, some parts of which are below sea level (in part a result of the 1987 Edgecumbe earthquake). Flash flooding can, however, affect any area where drainage is restricted or unable to cope with unusually heavy downfalls. Flooding may also bring with it problems and hazards of landslip on any of the steeper soils of the region. An eruption or earthquake may also cause changes in drainage . landslides blocking rivers or rapid overspill of lakes like Tarawera from the present outlet. These events could cause floods in several river catchments. Major events will affect both rural and urban areas simultaneously. Urban stormwater flooding (for example, Utuhina Stream in Rotorua or Waimapu in Tauranga) are district events and may be caused by localised thunderstorms in the smaller catchments.
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Geothermal Systems
Within and around the recognised thermal areas there is an ever-present possibility of hydrothermal eruption, caused by superheated underground water undergoing a drop in pressure and flashing to steam. The consequent expansion of the steam is capable of producing large craters and scattering debris over a wide area. Minor hydrothermal eruptions are common within the thermal areas. Read more...
Hazards from outside BOP
Hazards that occur in regions outside of the Bay of Plenty can also affect people and communities in the Bay of Plenty.
Landslides and Debris Flows
Erosion and slope failure is common throughout the Bay of Plenty. Land instability is often made worse by human activities.
Tornado
Tornados frequently occur in the Bay of Plenty but are much smaller than the very large ones that occur in the midwest of the United States.
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Tsunami
The most common cause of tsunami is submarine seismic activity, in which a large area of ocean floor is abruptly displaced by a major fault movement. In the Bay of Plenty, there are a number of local and regional sources that could result in a tsunami. These include volcanism in the Tonga/Kermadec system, landslides in the Hikurangi Trough, eruption of Mayor Island, fault movement within the offshore Taupo Volcanic Zone and slope failures on White and Whale Islands.
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Volcanic hazards
The Bay of Plenty Region encompasses a wide range of volcanic sites within its territorial boundaries, each capable of producing a risk to the public and to infrastructure. The region may also be affected by eruptions occurring in other volcanic centres i.e. Taupo, Egmont (Taranaki), Tongariro National Park, Auckland, and Kermadecs. Submarine volcanoes to the north-east of White Island present additional risk.
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Pandemic
Pandemics are the spread (potentially rapidly) of a disease across a wide geographical area. The widespread occurrence of a disease can overload medical infrastructure and can cause community disruption through limitations on movement and contact.
