Probabilistic flood warnings – Do eight out of then people prefer them?

Lumbroso, D. and Twigger-Ross, C. and Orr, P. and Kashefi, E. and Walker, G. and Cotton, J. (2009) Probabilistic flood warnings – Do eight out of then people prefer them? In: 44th Defra Flood and Coastal Management Conference, 30th June - 2nd July 2009, Telford, UK.

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Abstract

The introduction of probabilistic flood forecasts by the Environment Agency over the next few years could provide flood incident responders with better information for managing flood events. The inclusion of probability in internal and external communications of flood forecasts and warnings however, presents challenges that need to be anticipated. It is often difficult to present probabilistic data in a concise and easily comprehensible manner. To address these challenges the Environment Agency commissioned research to investigate the following: • The current “best practices” used to communicate probability and uncertainty in warnings for a range of natural hazards worldwide; • The extent to which professional partners and the public comprehend information about probability both generally and with respect to flood warnings; • What Environment Agency staff, professional partners and the public require and how they would use probabilistic flood warnings to improve their response to floods. The current practice review indicated that there is no single effective approach to communicating probabilistic and uncertainty information as communications are interpreted within personal, social or institutional contexts. The research demonstrated a high variability in the interpretation of qualitative descriptions of uncertainty and understanding of quantitative descriptions of uncertainty. A series of workshops and focus groups were held with Environment Agency staff, professional partners and the general public to gain a better idea as to how probabilistic flood warnings could be communicated effectively to meet their respective needs. These indicated that there was general support from Environment Agency staff and professional partners for the introduction of probability-based flood warnings in principle. Certain forms of probabilistic warnings were found to be “useful” by 88% of the Environment Agency flood incident management staff who replied to a survey undertaken as part of the research. The primary benefit of probabilistic warnings was seen as an increase in lead time which would provide the potential to prepare for a flood more effectively. Professional partners indicated that regular updating of probability estimates would enable the response to be adapted as knowledge about the impending situation developed. However, some professional partners also expressed concerns that probabilistic warnings might be misinterpreted by the public and indicated that such warnings should only be used for organisations with civil contingency responsibilities. The research carried out will help the Environment Agency to determine what new methods for issuing warnings and disseminating flooding information will most be most useful to Environment Agency and partner organisations’ staff.

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