Consequences can be defined in many units or terms such as loss of life, stress, material damage, environmental degradation and so on. Moreover, it is possible to measure this consequence qualitatively (such as “an area of high flood risk”), quantitatively (such as “value of a damaged house”) and an infinite number of shades and combinations of both. Thus it is inevitable that the usage of the term risk is always defined according to the task; each project should be encouraged to state an explicit definition within the framework of their particular application, which can be openly challenged or endorsed.

Fundamentally, it is difficult to adapt a unique definition for consequences, which includes a restricted group of variables or outcomes. Thus the consequence is perhaps best defined and redefined by the problem at hand (e.g. justifying flood defences by risk of damage argument). Therefore, it is justified to adopt any definition as long as it can be justified. F

However, if the problem is extended hazard parameters can be transformed, by the use of an additional impact model, into a quantitative consequence e.g. damage costs or actuarial costs of loss of life. Any individual definition of consequences will be conditional on the underlying assumptions of the impact model, which may have its own uncertainties. The assignment of a single cost to the impact of a water level or velocity is very difficult as it requires a strict definition (such as what is the value of human life or stress). Even very simple costs cannot be assigned without uncertainty. For example, several methods exist to assign a cost to the damage of an inundated housing estate, but they have to be based on generalizing assumptions such as the average value of house content. Although, it might be possible to quantify an average value from past insurance payments and model projections of future costs, it is also obvious that the value of individual properties will differ. Therefore, a distribution of the uncertainty around the integral of cost distribution is required.

References

Kelman, I. and Spence, R., 2003. A flood failure flowchart for buildings. Proceedings Of The Institution Of Civil Engineers-Municipal Engineer, 156(3): 207-214.

Slovic, P., 1987. Perception of risk. Science, 236: 280–285.

Wilson, C., 1990. Education and risk, in Hazards and the Communication of Risk. In: J. Handmer and E. Penning-Rowsell (Editors). Gower, Brookfield, pp. 53–68.

Acknowledgements: This Glossary is modified from Gouldby and Samuels, 2005, Language of risk – project definitions. FLOODsite Report T34/04/01

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Risk and Uncertainty (Description and Definition)