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Greater consideration of liquefaction risks urged by Christchurch report

Land development rules in Christchurch, New Zealand failed to take account of liquefaction risks, according to a new report published this week.

The final report from the Canterbury Earthquakes Royal Commission into the effects of the earthquakes in 2010 and 2011 said that too many buildings had to be demolished due to liquefaction damage.

The report called for better provision for the acknowledgment of earthquake and liquefaction risk in the various planning instruments that are made under the Resource Management Act 1991. The commission said that the Resource Management Act 1991 should more explicitly acknowledge the potential effects of earthquakes and liquefaction.

The report stated: “One way of minimising the failure of buildings in the future is to ensure that the land on which they are developed is suitable for the purpose. Having said that, we need to  emphasise that it is not possible to predict with any certainty when an earthquake will occur and, in reality, the public and private investment in the country’s cities is such that it is not realistic to redirect development from the existing central business districts.”

Risks of liquefaction and lateral spread should be considered when zoning for new development areas is being planned in order to minimise the effects of future earthquakes.

 

Recommendations

  • Sections 6 and 7 of the Resource Management Act 1991 should be amended to ensure that regional and district plans (including the zoning of new areas for urban development) are prepared on a basis that acknowledges the potential effects of earthquakes and liquefaction, and to ensure that those risks are considered in the processing of resource and subdivision consents under the Act.
  • Regional councils and territorial authorities should ensure that they are adequately informed about the seismicity of their regions and districts. Since seismicity should be considered and understood at a regional level, regional councils should take a lead role in this respect, and provide policy guidance as to where and how liquefaction risk ought to be avoided or mitigated. In Auckland, the Auckland Council should perform these functions.
  • Applicants for resource and subdivision consents should be required to undertake such geotechnical investigations as may be appropriate to identify the potential for liquefaction risk, lateral spreading or other soil conditions that may contribute to building failure in a significant earthquake. Where appropriate, resource and subdivision consents should be subject to conditions requiring land improvement to mitigate these risks.

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