Dam shame: what really caused Valencia’s floods?

Who is to blame for the devastating floods that hit Valencia on 29 October? The mob that surrounded King Felipe at the weekend and drove Prime Minister Pedro Sanchez out of town with a hail of mud and stones was angry at the failure to forecast the flood and warn people to get out of its way. The BBC would like us to be angry at man-made climate change for causing the storm – putting out a headline the very next day: ‘Scientists say climate change made Spanish floods worse.’

Yet Valencia had a similarly terrible flood in 1957, in which 81 people died, long before climate change became the go-to excuse for any bad weather. After that flood, to prevent a recurrence, the Spanish government built a string of dams in the hills to hold back water and diverted the Turia river away from the city. For more than six decades the system worked well. Why did it fail this year? Because the unusually warm sea made for an unusually bad storm, say some.

Yet charts of rainfall in Spain show no trend towards a higher frequency of more extreme downpours. The data analyst Jose Gefaell published a graph this week of the number of rainfall events in Spain in which more than 100 litres fell per square metre in 24 hours. It shows, if anything, a slight decline. The three worst such downpours all happened in the province of Valencia – but in November 1987, before global warming apparently kicked in.

In the past few years, the Spanish government has been removing dams at a furious rate. Under a European Union programme to encourage the restoration of rivers to their wild state for the benefit of fish migration, Spain set about dismantling barriers of all kinds.