UK flood review overlooks rising danger of flash floods
Flash flooding is a more serious threat to homes and infrastructure than river or coastal flooding due to the UK’s outdated drainage and sewage network and the concreting of land for development, argues The Guardian in an opinion piece. According to the Met Office, extreme rain has become more frequent. However, flash flooding was not included in last week’s National Flood Resilience Review. Maps created for the Environment Agency in 2013 revealed that three million properties in England were vulnerable to flash flooding, as opposed to two million from river and coastal floods. Most flood-related insurance claims also relate to flash floods.

Flash flooding, which struck a swathe of southern and eastern England on Friday, is a greater threat to homes, roads and railways than river or coastal flooding. Yet it was completely excluded from the government’s National Flood Resilience Review, published last week.

Worse, the risk of flash flooding is rising, as climate change leads to more intense, more frequent rainstorms: the Met Office has shown that extremely wet days have become more common. On Friday, half a month’s rain was dumped in one day.

The problem is the overloading of Britain’s antiquated drainage and sewer networks, compounded by the continued concreting over of land for development. The surface water can neither be absorbed or quickly drained away, leading to flash floods.

Ministers cannot say they were not warned. Flash flooding was the principal cause of the most damaging floods in UK history, which in 2007 caused over £3bn of damage, caused 13 deaths and was classified by the Environment Agency (EA) as a “national disaster”.

In 2013, new maps from the EA showed 3m properties were at risk from flash flooding in England, compared to 2m from river and coastal flooding. Most insurance claims made each year for flood damage are because of flash floods and there are at least 20,000 sewer overflows a year in the UK.

Risks to transport have also been identified: Network Rail is monitoring 200 “high risk” earthworks – embankments and cuttings vulnerable to washing away. In April the Guardian revealed that 57 tube stations are at high risk of flash flooding, including Manor House which flooded on Friday. The London Underground report said it was “only a matter of time” before serious flooding strikes.

After the 2007 disaster, the Pitt review led to new laws in 2010 to implement the use of sustainable drainage systems, which provide safe areas for water to pond. But the provisions were never implemented and instead a voluntary system asking developers to follow these practices was put in place.

But it has not worked: the government’s official advisers, the Committee on Climate Change (CCC), found that just 15% of planning applications in areas of flood risk incorporate sustainable drainage measures and in 2015 the CCC warned ministers their plans were inadequate. However, in May, the government successfully opposed a plan to make sustainable drainage compulsory, and to make developers increase the capacity of drains to which new homes are connected.

“The National Flood Resilience Review team was told it was a mistake to exclude surface water flooding from consideration on the basis that the last two major flood events had been river flooding,” said Bob Ward, policy director at the Grantham Research Institute on Climate Change and the Environment at the London School of Economics.

“We know our major cities, including London, are vulnerable to surface water problems,” he said. “But the UK remains at risk because the government refuses to confront the problem. The main problem is the inadequacy of the drainage system, which even nine years after the 2007 floods are still not up to the task.”

The EA maps shows that one home in particular is at risk of flash flooding: No 10 Downing Street. Perhaps this might spur prime minister Theresa May to finally take meaningful action.