Why Accurate Flood Warnings Still Fail: Behavioural Mechanisms of Uncertainty Interpretation and Implications for Impact-Oriented Services

Impact-based forecasting uses hydrometeorological information to trigger timely early actions, but real-world events show a gap between early warning and action. This paper addresses this bottleneck by examining how people interpret uncertainty in warnings and the impact this has on their actions.

We introduce the Uncertainty Lens Framework (ULF), which analyses how perceived uncertainty shapes threat, ownership, and coping appraisals in flood risk contexts. The ULF combines Protection Motivation Theory, decision heuristics and the Safe Development Paradox to explain why uncertainty can trigger protective action in some settings but lead to delay, denial or delegation in others. In this study, we apply the ULF to the 2021 flood in Germany, using quotations from newspapers and open-ended survey responses that capture the reasoning of affected residents during the event.

Three 'illusions of safety' that suppress early action emerge: (1) experience-based normalisation ('we've seen floods before'), (2) responsibility delegation ('someone else will handle this'), and (3) overconfidence in systems and protection ('the infrastructure/authorities will protect us'). These illusions are reinforced when uncertainty is implicit, inconsistently acknowledged or communicated without stable anchors to help people contextualise unprecedented escalation.

We therefore advocate proactive uncertainty management also for impact-oriented services and warning systems. Rather than trying to eliminate uncertainty, services should incorporate it into risk communication and policy design by deliberately establishing anchors and availabilities that help people understand residual risk from immediate and potential future exacerbation. Crucially, uncertainty communication must be embedded in sustained community-level engagement and long-term risk awareness so that warnings issued during an event are interpreted in the context of shared mental models, established trust relationships and preparedness measures.