Beyond flood hazard. Mapping the loss probability of pedestrians to improve risk estimation and communication

The effective communication of flood hazard and risk is a necessary step to foster preparedness and resilience, hence reducing the detrimental impacts of flooding events. Classical flood maps, which show flow depth and velocity, have often proved to be incomprehensible to the majority of people. Some recent studies used color maps to convey the spatial distribution of diverse hazard indexes that, accounting for both water depth and velocity, are intended to communicate the hazard degree in a more intelligible way. It is first shown that these hazard indexes have some inherent limitations, as for example the implicit assumption of a linear relationship between flood hazard and flow velocity. As an alternative, we propose to map the loss probability (LP) of pedestrians exposed to floodwaters, which is a physics-based and data-consistent risk index accounting for both hazard and vulnerability. LP can be easily computed and allows for a sounder estimation and a more effective communication of flood risk to the general public.

Automated summary

The effective communication of flood hazard and risk is crucial in reducing the detrimental impacts of flooding events. Traditional flood maps are often difficult to understand, leading to the use of color maps for better communication. However, these hazard indexes have inherent limitations. Therefore, the use of a physics-based and data-consistent risk index, such as the loss probability (LP) map, is proposed for a more accurate estimation and communication of flood risk.