Cascade vulnerability for risk analysis of water infrastructure

Abstract

One of the major tasks in urban water management is failure-free operation for at least most of the time. Accordingly, the reliability of the network systems in urban water management has a crucial role. The failure of a component in these systems impacts potable water distribution and urban drainage. Therefore, water distribution and urban drainage systems are categorized as critical infrastructure. Vulnerability is the degree to which a system is likely to experience harm induced by perturbation or stress. However, for risk assessment, we usually assume that events and failures are singular and independent, i.e. several simultaneous events and cascading events are unconsidered. Although failures can be causally linked, a simultaneous consideration in risk analysis is hardly considered. To close this gap, this work introduces the term cascade vulnerability for water infrastructure. Cascade vulnerability accounts for cascading and simultaneous events. Following this definition, cascade risk maps are a merger of hazard and cascade vulnerability maps. In this work cascade vulnerability maps for water distribution systems and urban drainage systems based on the 'Achilles-Approach' are introduced and discussed. It is shown, that neglecting cascading effects results in significant underestimation of risk scenarios.

Development of an urban drainage safety plan concept based on spatial risk assessment

“…For instance, the interruption of the power supply for an emergency outlet pump and a fluvial surcharged outlet, caused by a thunderstorm, are likely to occur simultaneously. For this reason, spatially depicted sensitivity analysis and cascade vulnerability maps can be used (Sitzenfrei, Mair, Moderl, & Rauch, 2011). Another example is shown in Cagno et al (2011).…”

An optimised total expenditure approach to sewerage management

“…The global objective of any infrastructure network rehabilitation programme is typically to improve performance or increase the network's reliability (Sitzenfrei et al, 2011 problem of how best to represent network performance is a topic that has generated much variance between different models and the published literature (Fenner, 2000). This is mostly due to the complexity of the problem in conjunction with the fact that network performance is often interpreted differently by different stakeholders.…”

Identifying Critical Elements in Sewer Networks Using Graph-Theory

“…This methodology is based on surcharged capacity, combined with surcharging water level, and is applicable to gravity systems. A second method, called the Achilles approach, is used in the planning tool for the identification of weak points during operation and emergency for the urban water infrastructure [13][14][15][16]. In this approach, the capacity of each conduit in a hydrodynamic model is reduced to (almost) zero and the hydraulic consequences are determined.…”