Probabilistic assessment of increased flooding vulnerability in Christchurch City after the Canterbury 2010-2011 earthquake sequence, New Zealand

Major earthquakes can extensively transform the above and below ground natural and built environments of cities, leading to decreased drainage system capacity and, ultimately, to Increased Flooding Vulnerability (IFV). This has been the case for Christchurch city in New Zealand, which experienced the 2010 to 2011 Canterbury Earthquake Sequence (CES). These seismic events were followed by extreme rainfall in March-April 2014, with much of the city experiencing damaging flooding. This paper uses data from a Christchurch case study to extend a recently-developed infrastructure damage simulation tool to the probabilistic assessment of earthquake-altered flood risk in a built environment. In particular, the focus is on the IFV caused by the earthquake-induced damage to the pipeline component of Christchurch’s storm water system, which was analysed at both connectivity and capacity levels. The probabilistic analysis was carried out via a plain Monte Carlo simulation, enabling the uncertainty affecting several key parameters to be taken into account. Final analysis results are presented spatially and in the form of cumulative distribution of flood height, the latter being an impact metric of great interest for infrastructure owners and emergency managers.