A long-term perspective of floods in the Spanish Mediterranean Basins from historical archives (1035–2020 CE)

An increase in globally occurring extreme precipitation events during recent decades has led to catastrophic floods, a trend projected to intensify in the future. In Spain, this issue is particularly critical due to the irregular and convective nature of Mediterranean precipitation and the high exposure of populated and agricultural areas, as well as transport infrastructure. However, the scarcity of long-term observational records limits our understanding of past flood variability and recurrence. Here we present a comprehensive analysis of historical floods in the Mediterranean basins of the Iberian Peninsula based on historical documentary records. The dataset spans from 1035 to 2020 CE and compiles 14,417 individual flood cases, grouped into 4,394 flood episodes, each characterized by location, geographic coordinates, river basin, and affected rivers. Additional information includes impacts on fluvial systems and infrastructure, classified by impact intensity, and in many cases, precise temporal resolution (day, month, year). Although the dataset represents a partial reconstruction of past reality, its magnitude provides robust insights into long-term flood dynamics. Spatial analyses reveal that events can range from basin-restricted to large multi-basin episodes extending from the Andalusian Mediterranean to the Ebro basin. Event duration varies widely and is not always correlated with spatial extent. From a seasonal perspective, most floods occur in autumn, though intense summer and spring floods are also recorded, the latter often linked to snowmelt in the Pyrenees and other mountain ranges. While a long-term increase in flood occurrence is observed, with a marked peak in the most recent decades, interpretations of recurrence variability must be made cautiously, as the record also reflects changes in exposure, increasing social impacts, and improvement in reporting capacity over time. This study constitutes a solid foundation for exploring hydroclimatic variability, societal vulnerability, and the evolving human–environment relationship over the last millennium.