Port Hills 3D rockfall modelling report

Report released 26 October 2012

The Canterbury Earthquake Recovery Authority (CERA) commissioned Geovert Ltd to carry out a three-dimensional (3D) rockfall modelling study on the Port Hills. The aim of this study, together with other investigations and work commissioned by the Christchurch City Council, was to help CERA to develop its policy advice to Cabinet regarding zoning decisions for rockfall and boulder roll-affected areas in the Port Hills.  

The 3D modelling was undertaken with the Hy-Stone programme developed at the University of Milano-Bicocca’s Dipartimento di Scienze Geologiche e Geotecnologie. The University’s mainframe computer was used to run the simulations, and Austrian rockfall specialists verified model outputs, and provided advice on likely energies and boulder trajectories. This information assisted Geovert to formulate advice around potential rock fall mitigation options for the Port Hills.

The 3D model involves generating many thousands of boulders of varying sizes and tracking the trajectories, paths and run out distances of these boulders based on the topography of the Port Hills. The benefit of this approach is that it provides strong evidence of how terrain influences boulder paths and travel distances.

The study presents the 3D modelling results in a graphical format according to geotechnical sectors used by the Port Hills Geotechnical Group (PHGG), a group of geotechnical consultants working for the Christchurch City Council. The areas investigated by the 3D model extended well over 65km2, and included key residential areas across all sectors on the Port Hills.

This information was used, in conjunction with other studies and expert advice, to assess what areas on the Port Hills are potentially impacted by rockfall, and where potential area-wide mitigation structures could best be located.

It is very important to note that the results of the 3D modelling study are the equivalent of a preliminary design level of detail for rock roll mitigation. This study was not intended to be used for detailed design or other rock roll mitigation assessment purposes.

This study did not consider the issue of boulder flux (i.e. areas where multiple boulders strikes could occur in a confined area). Boulder flux occurred in the Port Hills. Boulder flux needs to be considered as part of any detailed rock roll mitigation design for the Port Hills.

Online viewer

This online viewer displays the Port Hills rockfall modelling data released 26 October 2012. This viewer allows the user to focus in on areas of interest and should be used in conjunction with the reports available on this page.

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Geovert rockfall modelling report

Port Hills 3D rockfall modelling, Christchurch, New Zealand [PDF 625KB]

Appendix A – Sector 1 Modelling Results [PDF 7.2MB]
Appendix B – Sector 2 Modelling Results [PDF 3.7MB]
Appendix C – Sector 3 Modelling Results [PDF 3.3MB]
Appendix D – Sector 4 Modelling Results [PDF 3.2MB]
Appendix E – Sector 5 Modelling Results [PDF 3.6MB]
Appendix F – Sector 6 Modelling Results [PDF 3.1MB]
Appendix G – Sector 7 Modelling Results [PDF 2.7MB]
Appendix H – Sector 8 North Modelling Results [PDF 3.7MB]
Appendix I – Sector 8 South Modelling Results [PDF 3.2MB]
Appendix J – Sector 9 Modelling Results [PDF 7.1MB]