The Role of Exposure in Risk Analysis for Critical Water Infrastructure

Abstract

Water systems are categorized as critical infrastructure. In this paper we aim to further improve risk analysis for water distribution and urban drainage systems, taking into account abnormal and critical conditions of the entire system. Usually, risk is calculated by consequence times likelihood or vulnerability times hazard, respectively. In this definition, hazard means a process, which generates a potential stress or perturbation to a system. Vulnerability is the degree to which a system is likely to experience harm induced by perturbation or stress. However, in this definition exposure to hazards is unconsidered. Exposure is the possible contact between system and perturbation or stress. Firstly, exposure matrices are developed by means of expert knowledge and literature review to relate hazard and vulnerability. By means of such newly developed matrices a coherent picture of exposure is given. Finally, the matrices are exemplary used in the frame of a risk assessment using a show case. Thus, it is demonstrated that exposure significantly influence the risk probability. A show case reveals that an unconsidered exposure results in a considerably overestimation of risk for contamination of water distribution system.