4 Taking a Risk-based Approach
4.1 Using a risk management standard
We recommend that councils use this risk-based approach, based on risk management standard AS/NZS 4360:1999, when they develop provisions for their district plans.
This risk-based approach combines the key elements of fault recurrence interval (section 7), fault complexity (section 8), and Building Importance Category (section 9).
Key points to remember about the fault recurrence interval, fault complexity, and Building Importance Category are:
- Fault Recurrence Interval: The longer the recurrence interval of an active fault, the lower the risk that the fault will rupture in the near future.
- Fault Complexity: A fault rupture with a wide and distributed deformation is lower risk than a narrow, well-defined fault line.
- Building Importance Category: The Building Importance Category shows the need for an assessment of the suitability of a building in a fault avoidance zone.
4.2 Summary of the steps
There are six steps involved in the recommended risk-based approach. Note that this approach depends upon accurate information and mapping of active faults. Identifying and mapping faults are part of the Gathering information stage of district plan preparation.
Step 1: Identify where the active faults are in the district. The Institute of Geological and Nuclear Sciences hold maps of these which can assist.
Step 2: Create "avoidance zones" around the active faults identified. Check to see whether the fault lies in a greenfield site or not, whether the area is already developed, and whether there is an expectation or not of future building.
Step 3: Identify the nature of the fault rupture hazard risk. To do this you need to ask what is the likelihood of rupture in the fault avoidance zone (ie, the Fault recurrence interval)? And what is the nature of the fault in the fault avoidance zone (ie, the fault complexity)?
Step 4: Analyse and evaluate the level of risk to subdivision and development. What is the proposed use of the site? What is the construction type proposed, and the nature of its response to fault rupture movement? (Building Importance Category).
Step 5: Treat the risk. What action should be taken to avoid or mitigate the risk within the fault avoidance zone?
- regulatory planning methods
- non-regulatory methods
- limiting the risk posed by the building.
Step 6: Monitor and review. Is the council achieving the outcomes which it established? Is there new information that needs to be considered? Do changes need to be made to the council's district plan?
