Warning cultures in practice: Shadow systems in local flood risk governance

Early warning reduces flood risk when forecasts are interpreted and converted into timely local action. In Luxembourg, a nationally centralised system, with no intermediate tier, places the next line of decision making immediately with municipalities. This paper examines how a structured shadow system emerges at the local scale to bridge gaps between national alerts and operational needs. Evidence is drawn from a focus group with municipal officials in a flood-affected community, including a flood-scenario exercise simulating an evolving rainfall event to examine decision-making under uncertainty. Thematic analysis shows that national flood alerts are generic, repetitive, and weakly linked to municipal thresholds for initiating preparedness measures. Ambiguous terminology, colour codes, and broad spatial and temporal framing limit their operational usefulness for local response. Frequent low-level alerts contribute to warning fatigue and erode trust. Officials construct meaning through institutional knowledge, lived experience, peer exchange, and heuristics. These locally embedded practices highlight the importance of scale, showing how municipal knowledge both localises and at times overrides national messages. The configuration strengthens local responsiveness but concentrates interpretive responsibility at municipal level without formal support, which can increase variability across jurisdictions. The analysis points to a need for impact-based, temporally precise, municipality-scale products with clear triggers and guidance co-developed with local officials and potentially residents, so that centrally issued forecasts can be converted into anticipatory action at the local level. • Municipal officials created a shadow system to interpret national flood alerts. • Local judgement and memory made warnings actionable at the municipal level. • Frequent low-level warnings caused fatigue and weakened attention to risk. • New warning terminology reduced clarity for preparedness and response. • Anticipatory action needs locally specific, co-developed warning products.