Deep water horizon: Flooding is becoming more frequent and less predictable

Reinsurance broker Aon Benfield has calculated that flooding was responsible for $27bn of economic losses in 2015, often in areas that never used to flood. That was a good year – the annual average loss over the last decade has been $48bn. Munich Re’s NatCatSERVICE shows a steady increase in global hydrological events.

Climate change is only half the story. Flooding has become more problematic as the number of people living in urban areas has increased. Whereas in 1950, only one-third of the global population lived in cities, or 746 million people, today its more than half, or 3.9 billion people.

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Not that it is simply a case of keeping the water out. One of the most difficult lessons for the public to digest is that we must learn to live with it. Urbanisation has changed the nature of flooding – built-up areas are less permeable and more prone to flash floods, which are far more difficult to predict.

Over the past decade, policy has shifted from building more robust defences, to making space for water. It also means accepting that buildings will flood, and making them more resilient.