An alternative definition of risk is proposed as risk being a function of the hazard, which is related to the risk source and the vulnerability, which is related to the risk object. The same hazard will not cause the same effect on all risk objects, Therefore, vulnerability is introduced as a system-dependent property to be the link between the hazard and the effect so that the combination of the occurrence of a hazard and the vulnerability of an object results in the effect. In risk communication indicators are helpful since they help to simplify the message that has to be communicated. Three examples (pluvial flooding of sewers, dissolved oxygen depletion in streams and discharge of chemicals to receiving waters) show that dependent on the risk problem possibilities for risk reduction lies either at the risk source or at the risk object. Therefore, it is important to have indicators that can be used when the possibilities of risk reduction are analysed.
Water Science and Technology, 2006, Vol 54, Issue 6-7, p. 441-450