Bridging the Gap Between Qualitative, Semi-Quantitative and Quantitative Risk Assessment of Pipeline Geohazards: The Role of Engineering Judgment

Geohazards are threats of a geological, geotechnical, hydrological or seismic/tectonic nature that can potentially damage pipelines and other infrastructure. Depending on the physiographic setting of a particular pipeline, a broad range of geohazards may be possible along the pipeline route. However, only a limited number of geohazards such as landslides, fault displacement, mining-induced subsidence, liquefaction-induced lateral spreading, and hydrological scour, which can result in permanent ground deformation or exposure of the pipeline to direct impact, typically represent credible threats to pipeline integrity. Identifying potential geohazard occurrences and estimating the likely severity of each occurrence in relation to pipeline integrity is an integral part of geohazard management, and overall risk management of pipelines. Methods for identifying and assessing the potential likelihood and severity of geohazards vary significantly, from purely expert judgment-based approaches relying largely on visual observations of geomorphology to analytically-intense methods incorporating phenomenological or mechanistic models and data from monitoring and field characterization. Each of these methods can be used to assess hazard and risk associated with specific geohazards in terms of qualitative, semi-quantitative, or quantitative expressions as long as uncertainty and assumptions are understood and communicated as part of the assessment. Engineering judgment is highlighted as an essential component to varying degrees of each geohazard assessment approach.