Probable loss estimation of infrastructure damage due to landslide hazard: an example of geotechnical risk assessment

With the rising cost of impact from natural hazards on public horizontal infrastructure (e.g. water supply networks), better management of natural hazards is required. The main options for managing the impacts from such events are risk acceptance, avoidance, mitigation and transfer (i.e. through insurance). Each of these options have a monetary cost. An optimal approach generally comprises a combination of options, which vary between asset types, locations and infrastructure owner requirements. To understand the costs and effectiveness of the risk management options, risk assessments are conducted to assess the likely damage and the associated reinstatement cost. This paper summarizes a case study that applied a model developed to assess the impact to council assets from seismic and co-seismic events (e.g. liquefaction and landslide) in order to estimate the probable loss. This paper focuses on the landslide hazard and risk analysis component. Using mapped historic landslides, the susceptibility of the geology and slope profile for future landslides can be quantified. This produced a landslide hazard factor which was grouped into a qualitative hazard descriptor. The output for the landslide hazard analysis was geospatially referenced to attribute assets to the modelled landslide risk. Through stochastic risk modelling, the total asset portfolio loss was modelled.