Risks depend on hazards and vulnerabilities against them. Hydrology is very much focused on the characterization of hazards. The susceptibility to these hazards strongly depends on the understanding and assessment of hydrological phenomena. Here hydrologists are challenged to provide the necessary information to the public. However, hydrology often fails to communicate with stakeholders and affected people about hazards. One problem of these communications is the insufficient consideration of the differences between aleatoric and epistemic uncertainties. In this contribution these differences are discussed. Some examples of ways to reduce epistemic uncertainties are presented.
