1 Introduction
Controlling the development of land on or close to active faults is a Resource Management Act 1991 issue. These guidelines provide direction on land use planning approaches for land on or close to active faults. They aim to help local authorities minimise the hazard risk and the time it takes for individuals, communities, and the government to recover from a fault rupture.
The guidelines aim to assist planners, emergency managers, earth scientists, and people in the building industry to avoid or mitigate the fault rupture hazard.
It is hoped that use of these guidelines will help to avoid or mitigate the risks associated with building on or close to active faults. Different planning approaches are appropriate in different areas - councils can establish appropriate policies and criteria which are more or less restrictive than those represented here if necessary.
A working party of representatives from the Institute of Geological & Nuclear Sciences, Geological Society of New Zealand, New Zealand Society for Earthquake Engineering, BRANZ, Earthquake Commission and Ministry for the Environment developed these guidelines. Consultation took place with members from various local authorities. The collaborative approach drew together a range of expertise from professions that have an interest in land use issues and hazard risk reduction.
Note that these guidelines are only concerned with the avoidance and mitigation of risk arising from active fault rupture. They do not discuss other earthquake-related hazards, such as strong ground shaking, liquefaction, uplift, subsidence, landslide and tsunami.
1.1 Why we developed the guidelines
New Zealand's precarious location at the edge of two converging tectonic plates means we are subject to natural hazards like earthquake shaking, earthquake fault rupture, and land deformation. As these tectonic plates continue to move, New Zealand will continue to be subject to earthquake-related hazards.
In March 2001, the Parliamentary Commissioner for the Environment (PCE) released the report Building on the Edge - The Use and Development of Land On or Close to Fault Lines. The Commissioner's investigation arose following public concern that local authorities were not able to adequately manage the use and development of land on or close to active faults.
The PCE report focused on the Building Act 1991 and the Resource Management Act 1991 (RMA). It reached a number of key conclusions:
- There is no technology to prevent earthquake damage to buildings built across faults.
- Few territorial authorities identify and plan for seismic hazards, despite their responsibilities for subdivision and land use.
- Practical guidelines are urgently needed to reduce the risks associated with fault rupture.
Recommendation 1 (below) of the PCE report was the catalyst for the development of these guidelines:
The Ministry for the Environment [is] working together with the Institute of Geological and Nuclear Sciences and other interested organisations with structural and geotechnical expertise to develop best practice guidelines for territorial authorities in avoiding or mitigating seismic hazard through the district plan process.
We suggest that users of these guidelines also read the PCE report, to gain an overview of active fault and land use issues.
1.2 Summary of the contents
The first part of this guide (sections 2-9) focuses on the need for a risk-based approach to planning for land use on and near active faults. It recommends that councils:
- identify active faults in their district, with maps that are at the right scale for the purpose
- create fault hazard avoidance zones on their district planning maps
- evaluate the fault rupture hazard risk within each fault avoidance zone
- avoid building within fault hazard avoidance zones where possible
- mitigate the fault rupture hazard when building has taken place or will take place within a fault hazard avoidance zone.
The main elements of the risk-based approach are:
- the fault recurrence interval, which is an indicator of the likelihood of a fault rupturing in the near future
- the fault complexity, which establishes the distribution and deformation of land around a fault line
- the Building Importance Category, which indicates the acceptable level of risk of different types of buildings within a fault avoidance zone.
The second part of this report (sections 10-11) discusses the role of regional councils and territorial authorities in planning for fault rupture hazard. Section 11 describes how councils can take a risk-based approach to establishing resource consent categories for buildings within a fault hazard avoidance zone.
