At a recent hydrology conference we ran an experiment in flood forecasting. The experiment investigated whether probabilistic information improved decision making. Participants were presented with six forecast hydrographs and were asked to decide whether to open the upstream flood gates for floodplain storage for which they had to compensate the farmer £15000, or to accept the risk and do nothing, in which case if the downstream town flooded they were faced with costs of £40000. In the first game the hydrographs included uncertainty bands showing the possible forecast spread. The second game showed the same six scenarios in a different order and without the uncertainty. bands.

From the 80 hydrologists who took part, three key outcomes were identified from this experiment:

• there is an improvement in ability of participants to correctly take action in response to forecast when probabilistic data is provided;
• there is a reduction in cost when probabilistic data is provided, particular from compensation for missed events;
• and there is evidence of a more risk averse approach when only deterministic data is provided.

The experiment was inspired by work at HEPEX and published research findings can be found through Ramos, M. H., S. J. van Andel, and F. Pappenberger. ‘Do Probabilistic Forecasts Lead to Better Decisions?’ Hydrology and Earth System Sciences Discussions 9, no. 12 (10 December 2012): 13569–13607. doi:10.5194/hessd-9-13569-2012.