A flash flood occurs when torrential rainfall exceeds the soil's absorption capacity and watercourse drainage in minutes to a few hours. It is Europe's deadliest meteorological disaster after heat waves.
In Spain
The Spanish Mediterranean coast is especially vulnerable due to its terrain (mountains near the sea), fast-response basins (ramblas), and urbanisation of flood-prone areas. The Valencia DANA of October 2024 produced over 400 mm in a few hours, causing catastrophic flooding. Urban soil sealing worsens the problem by preventing infiltration.