Interdependency Modelling in Risk Analysis
Failures of critical infrastructures can represent a threat both to people, economy and societal functions and to national security. So, thorough risk analyses of infrastructures are required to reduce the probability and mitigate the consequences of fail
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Interdependency Modelling in Risk Analysis Per Hokstad, Ingrid Bouwer Utne and Jørn Vatn
Abstract Failures of critical infrastructures can represent a threat both to people, economy and societal functions and to national security. So, thorough risk analyses of infrastructures are required to reduce the probability and mitigate the consequences of failures. The interdependencies between infrastructures can be strong, but are seldom accounted for in current analyses. This chapter presents a method for assessing these interdependencies and also provides an example. The analysis is part of an overall cross-sector risk and vulnerability analysis (RVA), see Chap. 3.
4.1 Steps of the Interdependency Analysis The total risk and vulnerability analysis (RVA) consists of three main phases (cf. Chap. 3). Phase 1 consists of analysis preparations. In phase 2, hazardous events are identified and analysed in a coarse way, as in a preliminary hazard analysis (PHA). Also, a screening is carried out to identify the hazardous events for which more detailed analyses are required. The detailed analyses (phase 3) may include an analysis of interdependencies, which is described in this chapter. A detailed interdependency analysis includes the following steps:
P. Hokstad (&) SINTEF Safety Research, Trondheim, Norway e-mail: [email protected] I. B. Utne Department of Marine Technology, NTNU, Trondheim, Norway J. Vatn Department of Production and Quality Engineering, Norwegian University of Science and Technology, Trondheim, Norway
P. Hokstad et al. (eds.), Risk and Interdependencies in Critical Infrastructures, Springer Series in Reliability Engineering, DOI: 10.1007/978-1-4471-4661-2_4, Springer-Verlag London 2012
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(1) Describe the undesired hazardous event, specify a corresponding scenario and identify relevant societal critical functions (SCFs), cf. Chap. 3. (2) Identify interdependencies. (3) Perform a semi-quantitative risk assessment of the scenario. (4) If needed, perform additional detailed quantitative analyses (optional). (5) Evaluate risk and suggest measures to reduce interdependencies and risk. (6) Analyse costs and benefits (optional). The above approach is based on having thorough system knowledge, but detailed skills in probability or statistics are not required (perhaps with an exception for steps (4) and (6)). These six steps are described below, and the approach will be illustrated by a case involving railway, electricity supply and ICT.
4.2 Step (1): Description of the Undesired Hazardous Event In step (1), the selected hazardous/undesired events are described more in detail than done in phase 2 (cf. RVA in Chap. 3). This means that physical location, environmental conditions and constraints, time and operational factors should be described. In addition, technical and organizational systems with physical objects that are directly affected need to be included. When these details of the hazardous event are specified, it is referred to as an (accident) scenario. Next, the SCFs that ar
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