Abstract
New Zealand’s South Island has variable seismic risk as a result of both plate boundary and local active faults. To reflect this variable risk, the Building Act separates New Zealand into zones of ‘low’, ‘medium’, and ‘high’ seismic risk. However, relative to other countries, a low risk designation still involves some exposure to seismic risk. Dunedin is one such example, where active faults close to the city have the potential to produce earthquakes of Mw 7 or greater, and generate a range of seismic and co-seismic hazards. While past research has highlighted the role of land use planning in mitigating natural hazard risks, little research has been conducted on how local government planners themselves understand the planning framework and apply various tools and approaches to reduce risk. To date, no research of this kind has focussed on low seismic hazard zones, where previous destructive earthquakes have occurred (e.g. Christchurch earthquake sequence (2010-2011). Guided by a realist methodological approach and using the low seismic hazard case study of Dunedin, this research utilised policy analysis and in-depth interviews to explore how planners can reduce seismic risk, and the challenges for decision-makers in applying current planning instruments.
This research found that New Zealand’s legislation provides planners with a range of planning instruments to mitigate earthquake hazards. These included land use planning methods which can be implemented to limit development in areas exposed to natural hazards. In addition, planners can create policy that is permissive of earthquake retrofits and adaptive re-use of heritage buildings, making it easier for building owners to obtain consent to undertake retrofits, thus hastening earthquake strengthening and reducing life safety risks. This research also found there are several logistical, social, and economic challenges that can hinder the implementation of these instruments in low seismic hazard zones. Firstly, Dunedin’s existing built environment presents a barrier as planners must contend with historic land use decisions and existing use rights, both of which can limit how planning instruments are applied. The large number of heritage buildings in the city requires significant financial investment from building owners to meet the requirements of the Building Act. However, the costs are prohibitive for many,and there is a risk of demolition by neglect, leading to a lingering presence of unstrengthened heritage buildings in Dunedin’s streetscape. This research also found that Dunedin’s low seismicity has led the public to accept the risk, which has resulted in opposition towards the implementation of polices to mitigate earthquake hazards, particularly if property values may decline; this can make councils hesitant to implement policies. Finally, the study revealed that local government planners would like further national direction on hazards, as current guidance has led to inconsistent hazard planning outcomes. Ultimately this research has contributed to a growing body of literature that seeks to understand how the New Zealand planning system can improve societal resilience to earthquake hazards.