| Consequence | An outcome or impact such as economic, social or environmental impact. May be expressed quantitatively (eg monetary value), by category (eg High, Medium, Low), or descriptively. |
| Decision/Event/Fault tree | Ways of describing a system and the linkages between different parts. Useful for identifying causes, tracing possible sequences of events, and investigating the effects of decisions. |
| Deterministic method | Method in which precise, single values are used for all variables and input values, giving a single value as the output. |
| Hazard | A situation with the potential to result in harm. A hazard does not necessarily lead to harm. |
| Monte Carlo modelling | A numerical technique for assessing the probability of different outcomes from two or more variables. |
| Probability | The probability of an outcome is the relative proportion or frequency of events leading to that outcome, out of all possible events. |
| Probabilistic method | Method in which the variability of input values, and the sensitivity of the result, are taken into account to give results in the form of a range of probabilities for different outcomes. |
| Probabilistic discounting | Use of probabilities and probability distributions in order to account for uncertainty when estimating present values of streams of cost, or benefit, over a period of time. |
| Probability distributions | Used to describe the likelihood of different values across the whole range of the variables, eg flood damage, extreme loads, particular storm conditions, etc. |
| Qualitative methods | Approaches which use descriptive rather than numerical values for assessment and decision- making. |
| Residual life of defences | The remaining time until a defence is likely to fail or no longer achieve minimum acceptable performance criteria in terms of serviceability or structural strength. (Criteria for failure need to be carefully considered.) |
| Return period | The average length of time separating extreme events (eg a flood) of a similar magnitude. |
| Residual risk | The risk which remains after risk management and mitigation. May include, for example, risk due to very severe (above design standard) storms, or risks from unforeseen hazards. |
| Risk assessment | Consideration of risks inherent in a project. |
| Risk management | The activity of mitigating and monitoring risks, which predominately occurs after the project appraisal stage. |
| Risk register | An auditable record of the project risks, their consequences and significance, and proposed mitigation and management measures. |
| Sensitivity testing | Method in which the impact on the output of an analysis is assessed by systematically changing the input values. |