How presentation format affects the interpretation of probabilistic flood risk information

In many European countries, flood awareness information is communicated through flood extent maps and probabilistic language. However, research suggests that probabilistic information is difficult to understand, and that presentation format affects understanding and risk perception. In this study, thirty participants participated in focus groups to explore responses to a flood extent map and completed a questionnaire to measure the effect of expressing the probability of flooding using different language formats on understanding and risk perception. Responses to the flood extent map reveal participants experienced difficulties interpreting the probabilistic information. In the questionnaire understanding was high across statements for both self-report and objective measures. However, the standard way of communicating risks, in terms of years per flooding event, evoked the lowest levels of understanding. For risk perception, there were differences in mean risk ratings across statements, and in general, people perceived the risk as greater when presented in terms of cumulative probability over a number of years, than in terms of the probability of a single event. This suggests that by making alterations to the standard format used to communicate probabilistic flood risk information it may be possible to increase understanding and awareness of the risks posed by flooding.