history of tsunami planning in new zealand

U H P H _ 1 4 : L a n d s c a p e s a n d e c o l o g i e s o f u r b a n a n d p l a n n i n g h i s t o r y | 361

History of Tsunami Planning in New

Zealand 1960 to the present

David Johnston Joint Centre for Disaster Research, Massey University – GNS Science, Wellington

[email protected]

Wendy Saunders Joint Centre for Disaster Research, Massey University – GNS Science, Wellington

Graham Leonard

Joint Centre for Disaster Research, Massey University – GNS Science, Wellington

James Beban Joint Centre for Disaster Research, Massey University – GNS Science, Wellington

Kim Wright

Joint Centre for Disaster Research, Massey University – GNS Science, Wellington

Stuart Fraser Joint Centre for Disaster Research, Massey University – GNS Science, Wellington

Tsunami awareness in New Zealand has evolved over the last 50 years since the 1960 Chilean tsunami, which struck New Zealand without official warning and caused significant damage, despite occurring at low tide. From 1960 to 2004 various measures were put in place, such as becoming part of the Pacific Tsunami Warning System, which led to improvements in official warning mechanisms.. However, surveys in 2003 showed that public understanding of tsunami risk and correct warning-response action was limited. Following the 2004 Indian Ocean tsunami the New Zealand government initiated an extensive review of national tsunami hazard, risk and preparedness. This review ranked tsunami risk to property potentially on par with that of earthquake and risk to life an order of magnitude greater. The Ministry of Civil Defence and Emergency Management (MCDEM) subsequently developed guidance for tsunami signage, development of evacuation zones, and dissemination of warnings. GNS Science has also produced guidance on how to incorporate tsunami modelling into land use planning. These initiatives represent significant steps forward in our preparedness for future

In UHPH_14: Landscapes and ecologies of urban and planning history, Proceedings of the 12th conference of the Australasian Urban History / Planning History Group, edited by Morten Gjerde and Emina Petrović (Wellington: Australasian Urban History / Planning History Group and Victoria University of Wellington, 2014).


tsunami, but there is a considerable way to go to ensure adequate awareness and preparedness of individuals and communities.

Keywords: Tsunami, warning systems, land use planning, Bay of Plenty, Wellington

Introduction

Major subduction zone earthquakes and tsunami, such as the Indian Ocean (2004) and Japan (2011) events, have focused attention on the potential impact of a tsunami of similar size and extent occurring locally to New Zealand. Central and local government, scientific agencies and communities have directed attention towards the risk from an earthquake and tsunami being generated at the Hikurangi subduction margin, off the east coast of the North Island and from other sources (local and distant). Many agencies and communities are reviewing their existing arrangements based on observations from Japan, and our knowledge of risk reduction options is leading to innovative policy and practice. However, much still remains to be done to reduce the risk from a future tsunami in New Zealand.

New Zealand has many potential local, regional and distant tsunami sources. However, because of the difficulties associated with studying undersea plate interaction seismicity, the Hikurangi subduction margin is potentially the most hazardous and least understood. Knowledge of the potential for significant earthquakes at the Hikurangi subduction margin has been developed over several years through studies of background seismicity and plate motions (e.g. Wallace et al., 2009). Paleoseismic and paleotsunami studies demonstrate the past occurrence of significant earthquake and tsunami at the Hikurangi subduction margin (Cochran et al., 2006). Previous numerical simulation of tsunami due to various earthquakes sources at the Hikurangi margin has demonstrated the potential for at-shore wave heights of 5m or more, and run-up to double that (Power et al., 2008). Development of a probabilistic tsunami model for New Zealand and high-resolution simulation of the onshore effects of local subduction zone tsunami are underway, as is development of a framework for detailed simulation of evacuation travel time for people at-risk from local tsunami (Fraser et al. 2012). Work is also underway to develop guidance for tsunami-resistant buildings, especially for use as evacuation structures (Leonard et al., 2011). Much of our understanding of the subduction hazard, particularly regarding frequency, remains uncertain. However, a significant local earthquake and tsunami, for which official warnings are not currently possible in New Zealand, is known to be a very real prospect.

This paper will outline the policy response to tsunami over the past 50 years, followed by specific risk reduction outcomes from recent events; namely land use planning guidance, evacuation planning and warning systems. Two case study examples are provided, which highlight the progress made in tsunami planning since 1960.

Policy response to tsunami hazards

Tsunami awareness in New Zealand has evolved over the last 50 years since the 1960 Chilean tsunami, which struck New Zealand without official warning and caused significant damage, despite


occurring at low tide (Johnston et al., 2008). From 1960 to 2004 various measures were put in place, such as becoming part of the Pacific Tsunami Warning System, which led to improvements in official warning mechanisms. However, surveys in 2003 showed that the public understanding of tsunami risk and correct warning-response action was limited (Webb, 2005). Following the 2004 Indian Ocean tsunami, the New Zealand Government initiated an extensive review of tsunami hazard, risk and preparedness (Berryman, 2005; Webb, 2005). This review ranked the tsunami risk to property to be potentially on par with that of earthquake and the risk to life an order of magnitude greater.

Table 1: National policy, council land community response to tsunami events, 1960-2013.

YEAR TSUNAMI EVENT / TRIGGER FOR CHANGE

NATIONAL POLICY RESPONSE COUNCIL AND COMMUNITY RESPONSE

1960 Chile NZ joins Pacific Tsunami Warning System

1990’s Some proactive councils erect tsunami signage, and other councils follow until present day.

2004 Indian Ocean 2005 National review of tsunami risk &

preparedness

2007 MCDEM reviewed their response to PTWC alerts and warnings

2008 MCDEM guidance for warnings, signage & evacuation

Community response plans developed in some areas

2010 NZ Coastal Policy Statements includes reference to tsunami risk

2011 Guidance for land use planners released on incorporating tsunami inundation maps into land use planning documents.

‘Blue lines’ project in Wellington (see case study)

2011 Tohoku (Japan) 2013 RMA reforms seek to include the

management of significant risks from natural hazards as a matter of national importance. MCDEM develop siren standard for use and technical requirements.

The development of New Zealand policy framework in relation to tsunami has been sporadic and has primarily been triggered by large international tsunami events (see Table 1). In particular, until the mid-2000,’s there has been little or no policy guidance in relation to tsunami. As a result, a significant amount of development has occurred on the coastal margins, with little or no consideration of this hazard and the associated risks. What is of particular concern is that many of New Zealand’s coastal communities have experienced significant growth and redevelopment since 1991 when the Resource Management Act 1991 (RMA) became law. This Act governs the use of land in New Zealand. Under this Act, tsunami is specifically identified as a natural hazard. The Act also requires Councils to plan and manage the effects associated with natural hazards (including tsunami). However, tsunami is often considered as a hazard that is best addressed through


emergency management actions, and as such, many planning documents throughout New Zealand do not attempt to address this hazard through appropriate objectives, policies and rules. The resulting effect has been that since 1991, there has been a significant increase in risk to people and property from tsunami. However, as demonstrated in the case studies provided, councils are now realising the risk that tsunami presents to their communities and the wider New Zealand economic and social wellbeing. As a result, they are beginning to proactively plan for this hazard to address future risks.

The RMA is not the only statute that addresses natural hazards. The current regulatory and policy approach to managing natural hazards – including tsunami – is well documented (Saunders & Beban, 2012; Saunders et al. 2007; Saunders et al. 2011). Ideally, any policy response should be a holistic, integrated approach that includes risk assessment, regulations, warning systems, construction, education, and exercises (see Figure 1). Each of these factors should not be considered independently as part of an integrated planning approach to managing tsunami risk.

Figure 1: A model for holistic risk reduction (adapted from Leonard et al 2008)


While the RMA does not specifically include risks from natural hazards, in 2006 the Environment Court ruled that considering tsunami risk was a statutory obligation under s6(e) of the New Zealand Health and Safety in Employment Act 1992 (Garside et al, 2009).

Policies and procedures for managing tsunami hazard and risk have been developed within a wider coastal management context. Blackett and Hume (2009) suggested that the constraints and division of responsibilities between management agencies under the RMA may influence decisions on how to respond to coastal issues. Many of the elements of this, and those in Figure 1, have been found in the approaches developed in Island Bay, Wellington, and in a greenfield area in the Bay of Plenty, which are discussed in the case studies to follow.

Land-use planning guidance

Until recently, there has been little regard to tsunami in land use planning in New Zealand. While the New Zealand Coastal Policy Statement (Department of Conservation, 2010) does specifically refer to tsunami (as a coastal hazard whose risk needs to be identified), there was no accompanying guidance on how tsunami could be planned for. In response to this gap, guidance was produced to aid decision makers on how to incorporate tsunami modelling into land use planning (Saunders et al. 2011). Based on a decision tree (Figure 2), the guidance leads the decision maker through the process of ascertaining if there is 1) a risk of tsunami; 2) if the risk is acceptable; and 3) how the risk modelling can be incorporated into land use planning or emergency management responses

Warning systems and public education

Following the national tsunami review in 2005 (Berryman, 2005; Webb, 2005), the Ministry of Civil Defence and Emergency Management (MCDEM) developed guidance for: tsunami signage, development of evacuation zones and evaluation of mechanisms for dissemination of warnings (MCDEM, 2008a, 2008b, 2010, Leonard 2008). However, only a minority of the public recognise that a natural earthquake warning is currently the only reliable warning for a locally-sourced tsunami; a tsunami originating within one hour of travel time. Communities nation-wide are continuing to lobby for tsunami sirens without a clear understanding of the distinction amongst (a) the ability of scientists internationally to accurately detect and forecast a local-source tsunami, (b) the ability to make a message heard and understood with a siren, and (c) the interaction necessary, and time for action required between scientists, emergency managers and technology if an official warning is to be produced. In the first tens of minutes after a large earthquake, scientists and emergency managers currently have no extra information upon which to turn on a siren, beyond the length and strength of the felt earthquake. The New Zealand CDEM approach, therefore, is to educate the public to evacuate immediately on a long (more than one minute) or strong (difficulty standing or walking) earthquake and never wait for an official warning. Attempting to generate official warnings for local earthquakes is currently akin to installing speakers that must be switched on (after checking a rain gauge) when it starts raining heavily, to tell the public to put on raincoats. International evidence shows (Fraser et al. 2012) that the inappropriate reliance on sirens has reduced response to natural warnings, therefore increasing the vulnerability of coastal communities (i.e. increasing fatalities through inaction or delayed action).


Figure 2: A decision tree for including tsunami inundation modeling into land use planning (Saunders, et al. 2011).

Case Study 1: Wellington

There are many sources for damaging tsunami in Wellington Region, and each source can produce a range of different events. Modeling all possible tsunami waves offshore and translating wave heights offshore into single event-based onshore inundation zones is not possible or affordable based on current resources, data and understanding of the multitude of potential tsunami sources for the region. A pragmatic and cautionary probabilistic approach can therefore be applied to generate an evacuation zone which envelopes all possible maximum events. The methodology used to create the evacuation zones, using a GIS-based attenuation rule applied to probabilistically-determined wave-heights at the coast, is described in detail in Leonard et al. (2009). This methodology also provides for two lesser evacuation zones (see Figure 3).


No one event can be expected to reach the boundary of the evacuation zone in all locations, due to wave orientation, attenuation, wave period and other influences, therefore this method will always produce over-evacuation. However, it is considered this approach is the safest and most reasonable given the uncertainty inherent in tsunami generation and behaviour, and the infrequency of major events. This zone, which applies to all felt major earthquakes and should be evacuated based on natural warnings without waiting for any official notification, is described and mapped by authorities as a nationally consistent “Yellow Zone”. The methodology used to generate this zone has been validated against recorded maximum inundation in the Tohoku tsunami, March 2011. The validation showed that for a 35m run-up value, the zone successfully encompassed the recorded inundation extent (Fraser and Power 2013). The boundary of the zone is delineated in Wellington by painting a blue line across roads, with “tsunami safe zone” written to be read facing uphill or inland. This “Blue Line Project” was devised by the local Island Bay community as part of their evacuation map planning, and has since become policy for the entire region and won an international emergency management award.

The multi-zone methodology also allows for smaller areas to be evacuated based on official warnings for distant source tsunami, when time, monitoring and expertise allows estimation of smaller wave heights and lesser inundation. For these events officials can advise the public whether to evacuate the Red Zone (basically a near-shore marine and beach exclusion zone for smaller, distant events) or the Orange Zone (a larger zone based on maximum distant events, which in most locations are smaller than potential inundation from local tsunami, but still include considerable on-land threat and inundation). Figure 3 (from Wright et al 2013) shows examples of evacuation zones within Wellington Region. It can be seen that the Yellow Zone encompasses the Red and Orange Zones, therefore when a natural tsunami warning is experienced the public response should be to evacuate all zones (Leonard et al., 2009). The “blue line’ is painted along the upper boundary of the yellow zone. Signs erected at the zone boundary indicate the beginning of the safe zone and the blue line reinforces the message in an innovative and highly visible way.

Figure 3: Examples of evacuation zone maps a) a draft evacuation zone map showing Wellington City; b) draft public education map for Wellington City; c) a completed community-scale map including evacuation routes and safe locations.


Public education regarding earthquake risk and tsunami evacuation zones comes under the domain of Wellington Region Emergency Management Office (WREMO). Wellington Region has recently amalgamated all CDEM units within councils to form a region-wide integrated body responsible for disaster planning and response. Community engagement including meetings and exercises, and publications and resources covering earthquake and tsunami preparedness (including maps of the evacuation zones and information about official and natural warnings) has been by WREMO. Their responsibilities also include planning for and coordinating post-event welfare provision, as well as liaison with communities, emergency responders and the national CDEM body prior to and during events (Wright et al, 2013). WREMO are currently integrating existing district tsunami response plans and establishing a scheme of work to expand and enhance existing arrangements form alerting to welfare to evacuation planning.

Case study 2 Bay of Plenty

Bay of Plenty has undertaken a comprehensive approach to incorporating tsunami hazards into its long term land use planning. For a number of years, the local councils in the Bay of Plenty Region have been aware of the potential threat that a tsunami from the Kermadec Trench presents to the Region. In 2010, the Bay of Plenty Regional Council commenced research that explored the risk from tsunami to the existing suburb of Papamoa as well as to future greenfield developments areas to the south east of Papamoa ((Beban, Cousins, Prasetya, & Becker, 2011) (Beban et al 2012a, 2012b). It is proposed that up to 40,000 people could be accommodated over the next 20 years in Wairakei and Te Tumu. The plan for managing this growth goes under the banner of SmartGrowth – a collaboration involving Tauranga City, Western Bay of Plenty District Council, and Bay of Plenty Regional Council working with industry and community groups (SmarthGrowth 2007).

As part of the SmartGrowth research, the risk to human life and the built environment was calculated for 12 tsunami scenarios, from local, regional and distal sources. The levels of risk that were calculated were assessed against the Proposed Bay of Plenty Regional Policy Statement (as notified) which identified acceptable, tolerable and intolerable levels of risk to human life. The acceptable, tolerable and intolerable levels of risk for building damage were based on preliminary risk levels in another GNS Science research program on risk-based planning. The levels or risk calculated assumed that no mitigation measures had been undertaken to reduce the risk to life or property Based on these risk thresholds, several of the larger scenarios resulted in an intolerable level of risk. These larger tsunami scenarios arrived on shore 50 minutes after fault rupture, meaning that people in these areas would not receive an official warning before the tsunami arrived.

The research suggested a number of measures that can be incorporated into land use planning to reduce loss of life and minimise economic losses. They include:

Retaining the existing sand dunes as they can be an important natural barrier for tsunami Designing future development to recognise the tsunami risk and include easily identifiable

access and egress routes Including mitigation measures in the design of coastal developments to reduce the effects of

a tsunami


Formulating a detailed evacuation plan for the coastal area and ensuring that routes are clearly identified and communicated to the public. Routes should lead to multiple safe areas where there is shelter, water, toilet facilities and cooking equipment.

A report was also commissioned for the suburb of Te Tumu, which is to accommodate up to 20,000 people, to investigate the provision of vertical evacuation refuges as a way to reduce the life safety risk to future occupants (Beban et al 2012b). To achieve an acceptable level of risk, 6000 people were required to be evacuated for a night-time event in Te Tumu, and 7000 people for a daytime event. The land use and emergency management implications of the provision of vertical evacuation refuges were also explored.

The tsunami research undertaken informed a revised SmartGrowth document that was released to the public for comment at the beginning of 2013 (SmartGrowth 2013). This 2013 SmartGrowth document more strongly identifies tsunami as a threat than its 2007 predecessor and also identified actions required to address the risk from the tsunami. While SmartGrowth document is non-statutory, it sets the framework for the future urban growth in the Bay of Plenty and is a document that would be considered when land use planning decisions are made. As such, the inclusion of tsunami into the SmarthGrowth documentation will ensure that this hazard is considered when future decisions on urban settlement patterns are made. This represents a significant change in the way that councils in New Zealand consider tsunami hazards and sets a strong framework that other councils could adapt to their respective jurisdiction.

Conclusion

Tsunami awareness in New Zealand has evolved over the last 50 years since the 1960 Chilean tsunami. Recent initiatives represent significant steps forward in our preparedness for tsunami, but there is a considerable distance to go to ensure adequate awareness and preparedness of individuals and communities. Arguably the greatest priority is to increase public understanding that local tsunami will not be preceded by official warnings, and that immediate self-evacuation is the best way to preserve life-safety. Land-use planning does provide opportunities to reduce or limit the growth of tsunami risk. Case studies, strategies and methodologies from regions well-advanced in tsunami planning can be utilised by other locations to assist communities and the authorities supporting them, in improving resilience to tsunami risk in New Zealand.

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history of tsunami planning in new zealand

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