Fault lines & liquefaction

GNS Science have provided new mapping of fault lines that have been identified within the district. Some of these faults are considered to be active, and are shown on the planning maps.

A Fault Awareness Area is located on either side of identified active fault lines, and is mapped to ensure that land owners are aware of the presence of a fault line before they decide to build. Within the awareness area special consideration should be given to geotechnical investigation and the design of building platforms.

Liquefaction is the process where, during earthquake shaking, sand and silt grains in wet soil are rearranged and the water in the spaces between the grains is squeezed. Pressure builds up in the water until the silt and sand grains 'float' in the water, and the soil behaves more like a liquid than a solid.

The liquefaction area is mapped to ensure that owners are aware of the risk from liquefaction and lateral spread prior to building to allow for evaluation and design in these locations (pdf, 887.7 KB). This is consistent with the Canterbury Regional Policy Statement, which sets high level policy direction that the Waimakariri District Plan must give effect to.

Questions and answers

What is a fault awareness area and what does it mean?

The fault awareness area is located on either side of an identified active fault line, and is mapped to ensure that land owners and service providers are aware of the presence of a fault line before they decide to build.   Within the awareness area special consideration should be given to geotechnical investigation and the design of building platforms.

 

Why is the liquefaction area included in the plan change?

The liquefaction area is mapped to ensure that owners are aware of the risk from liquefaction and lateral spread prior to building to allow for evaluation and design in these locations. This has been included on LIMs for some time. This is consistent with the Canterbury Regional Policy Statement, which sets high level policy direction that Waimakariri District Council must give effect to.

What effect will the plan change have on my property values?

There are many factors which affect property values. The risks posed by natural hazards are one of them. A registered property valuer may be able to advise on any enquiries regarding property value.

What effect will this have on my insurance?

The Council cannot provide guidance or indications of potential consequences for insurance resulting from the draft proposed plan change.  If you would like to know more about this, you should contact your insurance provider for further information about any insurance implications.

Why has the Council previously allowed development to happen in new residential areas that are at risk to flooding or liquefaction?

Since the previous rules were developed the Council has received hazard and flood modelling information which increases the understanding of risks posed by natural hazards.

The information that is available about natural hazards wasn’t available to the extent that it is now. Now that this information is available, the Council has a responsibility to manage and minimise risks to protect people and property. The District Plan needs to be updated to respond to this new information and plan for management of risk situations.