Slope risk analysis supporting post-disaster recovery: The 2016 Kaikoura Earthquake

Tim Mote, Meg Wimberley, Mark Easton, Mark Skinner, Doug Mason and Fergus Cheng

On 14 November 2016 a M7.8 earthquake caused significant localised damage to transportation infrastructure around Kaikōura, NZ. The strong earthquake-induced ground motions in the near-source region resulted in substantial rockfall, translational landslides, and channelized debris flows. The closure of SH1, the Inland Kaikōura Road and the Main North Line railway effectively cut off all land routes into Kaikōura.

The North Canterbury Transport Infrastructure Recovery Alliance (NCTIR) was established to rebuild and reopen the coastal routes. To better understand current and future risk to road users, slope risk analyses were carried out following the NSW Roads and Maritime Services 2014 Slope Risk Analysis methodology (NSW RMS SRA 2014). Various risk scenarios were considered reflecting the temporal change in hazards, likelihood, and consequences through the post-disaster recovery process. The core approach of the NSW RMS SRA methodology was applied to consider multiple risk scenarios in order to support the post-disaster activities. A total of ~70 slope risk analyses were carried out over 10km of SH1. Due to the large spatial extent of the slopes and source zones, automation of geospatial analysis of LiDAR derived digital elevation models increased efficiencies in the analysis and documentation.

The application demonstrated that rapid post-disaster risk reduction practices like traffic control and temporary barriers were effective in temporarily reducing risk to acceptable levels. The NSW RMS SRA can be used throughout the post-disaster response and recovery process to understand risk to road users in re-opening the road and optimise the balance of proposed risk mitigation options between risk reduction, costs and impact to road users.