There may be a range of events that are not identified in this plan that will require the community response plan to be activated. The value of this plan is that it is flexible in terms of activation and implementation for any event. The principles of response are generally the same.
There are two dams in the Takaka River catchment to consider. The first is the landslide dam formed in the 1929 Murchison earthquake that now impounds Lake Stanley. This dam is massive in comparison to the size of the lake it impounds and is not considered at risk from structural failure. Another major landslide into the lake may cause sufficient water elevation to overtop the existing dam structure.
The second dam is the Cobb River earth dam forming Cobb Lake. This dam was completed in the mid 1950s and is regularly monitored and its performance maintained by TrustPower under a Dam Safety Assurance Programme.
Golden Bay is exposed to frequent heavy rainfall from both the North and West quarters. Flood risk is high, with farm activities carried out extensively on flood prone areas. Takaka township is likely to be flooded again, the last major event occurring in 1983. The Aorere estuary at Ferntown floods regularly, a significant heavy rainfall event occurred in 2010.
Golden Bay contains a variety of rock types of different ages. Hard rock types are dominant and, despite numerous planes of weakness and being subject to high intensity rainstorm events, they are generally competent and not subject to large scale slope instability.
Nevertheless, small scale superficial failures are common when the ground becomes water saturated and rock falls are relatively common where hard rock types form escarpments and very steep slopes. Seismic shaking, even during lower intensity earthquake events, can initiate rock falls from escarpments.
It is considered that for landslip to occur on a scale requiring CDEM involvement this would be in conjunction with a major storm or earthquake event.
Being within central New Zealand, Golden Bay has a high risk of damaging earthquakes. No currently active faults are known to be present within onshore Golden Bay.
Many of the major faults that mark significant topographic changes, such as the Wakamarama and Pikikiruna faults along the toes of the eastern and western sides of the Wakamarama and Pikikiruna ranges respectively, are potentially active.
Offshore northwest of Cape Farewell the Cape Foulwind Fault, which trends northeast parallel to the Wakamarama and Pikikiruna faults, is regarded as active although information on it is very limited.
While there is no risk of volcanic activity in Golden Bay it would be possible for volcanic ash from Mt Taranaki or the Taupo Volcanic Zone to spread south, particularly under northeasterly winds.
Tsunami and Storm Surge
A tsunami is a fast moving wave created by a sudden movement of the seafloor. Triggering events include earthquakes (normally ^M5) and their associated fault ruptures, volcanic eruptions, coastal landslides and submarine (underwater) slides.
The tsunami risk to Golden Bay is perceived to be less significant especially compared to other risks the community faces. However a Taranaki earthquake might trigger a tsunami entering Golden Bay from the west.
Golden Bay has on average around one ex-tropical cyclone pass near-by each year, putting the region at some risk. Changing weather trends means that cyclones may occur more frequently and with higher than previous destructive force. The cyclone risk is considered a medium risk in Golden Bay.
A risk exists for significant fire events throughout the Golden Bay area but there are sufficient natural barriers to make escalation to a civil defence emergency unlikely.
The settlement of Milnethorpe is considered a high risk due to the introduction of eucalyptus in close proximity to residential homes.
Chemical Event (HAZNO)
The potential for a chemical related event that is beyond the control and management of the emergency services is considered low. However, the potential for a LPG incident or major petrol spill, for example, could lead to the activation of the community response plan and evacuation measures being implemented.
Criminal Event - P Lab / Firearms / Hostage
The possibility of a criminal event exists in every community. As was witnessed in the Aramoana massacre 1990 and the Napier siege 2009.
The NZ Police are the lead agency, however, this type of event may result in activation of the EOC to coordinate public safety measures such as road closures, evacuation and standby of emergency services.
In 2009 planning was put in place at the national and regional levels for an influenza pandemic. The lead agency in planning and responding to these emergencies is the Ministry of Health (national) and the Nelson Marlborough District Health Board (regional). The Nelson Tasman CDEM Group is closely involved in work to support the NMDHB in our region. The Nelson Tasman CDEM Group Pandemic Plan sets out regional CDEM arrangements and basic principles to be followed.