Planning for resilience of water networks under earthquake hazard

Water networks are vulnerable to earthquakes and failures of network components can result in a lack of availability of services, sometimes leading to relocation of the community. In New Zealand, there are statutory requirements for the water network providers to address the resilience of infrastructure assets. This is done by identifying and managing risks related to natural hazards and planning for appropriate financial provision to manage those risks. In addition to this, the impact from the Canterbury region earthquakes has accelerated the need for understanding the potential risk to critical infrastructure networks to minimise socio-economic impact. As such, there is a need for developing pragmatic approaches to deliver appropriate hazard and risk information to the stakeholders. Within the context of improving resilience for water networks, this study presents a transparent and staged approach to risk assessment by adopting three significant steps: (i) to define an earthquake hazard scenario for which the impact needs to be assessed and managed; (ii) to identify vulnerable parts of the network components; and (iii) to estimate likely outage time of services in the areas of interest. The above process is illustrated through a case study with water supply and wastewater networks of Rotorua Lakes Council by estimating ground motion intensities, damage identification and outage modelling affected by number of crews and preferred repair strategies. This case study sets an example by which other councils and/or water network managers could undertake risk assessment studies underpinned by science models and develop resilience management plans.