PREPARED - Major risk categories and associated critical risk event trees to quantify D2.3.1

The report focuses on defining risk and uncertainty, and details methods related to risk assessment, uncertainty analysis and propagation. 'Risk' is introduced and defined, followed by an introduction to risk assessment, with literature review details of several relevant methodologies, all of which could be used in the risk analysis of (urban) water systems. A summary of the most used methods is provided. Deterministic quantitative risk assessment (QRA) is introduced, followed by the recognition that there is always some inherent uncertainty when dealing with the key facets of determining risk - probability analysis and determination, followed by consequence analysis. Because of this, uncertainty as a concept is introduced, along with the most likely sources of uncertainty, followed by the details of suitable methods that could be used in order to propagate estimated uncertainty through a risk assessment. This leads to a discussion on stochastic QRA, which aims to account for the uncertainty using the methods described. Finally, some preliminary risk categories for water systems are outlined and these are subsequently broken down to examine some potential social, environmental and economic risks posed by the various hazards that may impact water systems in the face of a changing climate.