Flooding caused by poor management and floodplain building

The Guardian 3 weeks ago

Poor management of the rural landscape along with global heating and building on floodplains are the main factors that led to the floods that have engulfed towns in northern England, according to experts.

Sheffield, Rotherham and Doncaster are among the places flooded, just 12 years after they were badly hit when the River Don burst its banks in 2007. Many affected areas, including Meadowhall shopping centre where customers were stranded overnight, lie within the river’s floodplain – low-lying land next to the river that naturally floods during high flow.

“This is only a problem if you develop floodplains by building houses, businesses and factories on them, which is obviously what we have done over the years, so to some degree, it’s a problem of our own making,” said Roy Mosley, head of conservation and land management at Sheffield and Rotherham Wildlife Trust.

The risk faced by floodplain communities is exacerbated by the management of land upstream of the city. Intensive animal grazing leads to short grass and compacted soil, which is less able to absorb and hold water. There are no longer enough trees and plants to absorb rain and stop it from running straight into the river, Mosley said.

There are similar problems in Derbyshire, where the River Derwent burst its banks last week, forcing hundreds out of their homes and businesses, and leading to the death of former county high sheriff Annie Hall.

Matt Buckler, head of nature recovery networks at Derbyshire Wildlife Trust, said the fact that fields below the river level remained dry while towns flooded exposed the problems with our rural land. “It would have been easy to reduce the level of the river by 10-15 centimetres by letting those fields flood.

“People last week said ‘Oh, we were very lucky, if the water had been a centimetre higher it would have come into the house’. So reducing flood levels by just one or two centimetres can have a massive impact on people’s lives.”

Increased flooding is the biggest impact on the UK of the climate crisis, according to the government’s official advisers, the Committee on Climate Change. In July, the CCC said there were no areas where the government was preparing properly for climate impacts, though it said flood planning was making progress – with the exception of flash flooding.

Met Office data shows the amount of rain from extremely wet days has increased by 17%, when comparing 2008-2017 records with those from 1961-1990. The two wettest winters on record were 2013-14 and 2015-16. The Met Office calculates that an extended period of extreme winter rainfall in the UK, similar to winter 2013-14, is now about seven times more likely because of climate breakdown.

One reason is that warmer air can contain more water vapour. Another likely reason is the effect of global heating on the jet stream. Its normal meandering across the nation appears to be slowing, meaning rain falls for longer on one region, increasing the risk of floods.

Mosley said: “The last big flood in [South Yorkshire] and in much of the country was in 2007. At one time that would have been considered a one-in-100 flood, but here we are now just 12 years later with another flood that is actually bigger. We’re going from something very infrequent to potentially something almost regular.”

The wildlife trust has worked on schemes such as the installation of the 4.5-hectare (11-acre) Centenary Riverside flood storage area in Rotherham. “Last week it was full to the brim and clearly if that water wasn’t there it would be somewhere else, probably in someone’s business,” said Mosley.

The organisation is also working upstream in the hills above Sheffield to install water storage ponds and ditches, plant trees and manage livestock grazing. “We’re encouraging farmers to plough across slopes rather than up and down slope, which is mechanically easier but all that does is create water channels for water to rush off the hills,” said Mosley. “We’re delivering these measures across 14 sites but it needs to be 400.”

The hills above Glossop, Derbyshire, in the foothills of the Pennines, where the wildlife trust is working to restore the moorlands. Photograph: Andrew Kearton/Alamy Stock Photo

Meanwhile the conservation organisation Moors for the Future is working in the Pennines, where the River Don originates, to restore the moorlands, which were degraded by air pollution from previous industrial activity. They are reintroducing sphagnum moss, which was killed off by poor air quality but can store huge amounts of water.

Chris Dean, head of programme delivery for the group, said that while these efforts would not solve flooding problems, they should be considered as important as man-made flood defences. “There is no difference in my mind between getting sphagnum moss back on the top of the hill and building hard defences alongside the river.”

A previous project carried out by the group on the River Kinder showed that moorland restoration can take 30% off the flood peak and reduce the time it takes water to leave the site by 20 minutes.

The burning and draining of moorland to boost game bird populations for grouse shooting has also been blamed for increasing the risk of flooding across Yorkshire.

In 2016, the planting of 40,000 trees above Pickering in North Yorkshire was credited with helping the frequently flooded town avert inundation during heavy rainfall by slowing the flow of water into the river and reducing its peak height. The £500,000 project was significantly cheaper than a proposed new flood wall.

MPs criticised the government in 2016 over insufficient funding for natural ways to prevent floods, including trees and putting logs in rivers to slow water flow. But scientists say that natural flood defences must be combined with conventional prevention techniques.

Prof Hannah Cloke, a hydrologist at the University of Reading, said that more work could be done on the floodplain as well as in the uplands. “You can retrofit houses to be more resilient. If you are building on a floodplain because there’s no other option at all, you can raise these buildings on stilts and make a space for the water to flow around the building. These technologies exist, but they are expensive and therefore are not popular with developers.”

Funding for flood defences in England was cut sharply after David Cameron became prime minister in 2010, delaying many schemes. It was restored after serious flooding hit many parts of the country. On Friday, the prime minister, Boris Johnson, said: “We are seeing more and more serious flooding – perhaps because of building, almost certainly because of climate change.”

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