The River Don has long caused flooding problems, but is it time that we looked to nature instead of turning to more costly engineering? Andrew Griffiths reports.
Sheffield may be the Steel City, but water has long been its flowing heart. While industrial success has been built on the power of the River Don, it has also been a constant threat to the city’s security when the rains came, and its banks burst and unleashed the destructive forces of a flood. The battle to control the river has been waged since the 1600s, when the Dutch engineer Cornelius Vermuyden first began to divert its flow.
Sheffield is built at the foot of moorland and the descent down to the city is short and steep. The summer floods of 2007 claimed the lives of two people and caused £30m of damage, then came the damaging storms of 2012.
The latest attempt to engineer the river is in the proposal stage – an £83m capital programme put forward by Sheffield City Council. The plans range from building flood defence walls in the city to building embankments and creating temporary flood areas higher up the river system to hold back the water during heavy rainfall.
Some of these temporary flood areas would result in the flooding of environmentally sensitive areas such as the one proposed in the Loxley Valley, and not everybody is happy about it. Some think such measures might not even be necessary if the council gave more consideration to other flood control strategies, such as Natural Flood Management (NFM).
Natural Flood Management has growing support. Until relatively recently, the predominant school of thought when dealing with the threat of flooding was to get the water off the hills and out to sea as quickly as possible. It didn’t work.
Now the pendulum is swinging towards slowing the rate at which rainfall enters the river. This can range from planting trees, to recreating blanket bogs and putting the bends back into rivers. When employed over a whole river catchment area the effect can be dramatic.
The number of high profile NFM projects is growing. In Pickering, in North Yorkshire, NFM measures have been credited with helping to save the town from last year’s Christmas floods. The announcement by Environment Secretary Andrea Leadsom that £15m has been ring-fenced specifically for NFM projects as part of the Autumn Statement has added further impetus.
Peter Worrall is a trustee of the Don Catchment Rivers Trust, and isn’t convinced that the council’s plans are the best answer. “Take the Loxley Valley, where there is a proposal for quite a significant embankment across the valley itself,” he says. “Putting a huge embankment across the river valley, and forcing the river to go through a culvert, it just seems a step backwards. We have spent decades trying to create our semi natural environments, but here we are planning to impose something that really is going to make a significant change.”
Worrall is a director of the environmental consultancy Penny Anderson Associates and has seen the effect NFM can have first hand.
He cites data from recent heavy rainfall which demonstrated a 10 per cent reduction in peak flows from NFM measures employed on only two per cent of land in the available catchment.
“That can be the difference between the water coming over your doorstep, or just being at your step.”
However, one of the obstacles preventing the uptake of NFM measures is its lack of large scale predictability with most of the available data relating to small field trials. Worrall accepts that Sheffield Council has made some positive noises about NFM, but he believes it has not fully explored the full benefits.
Prof Alastair Driver was until September of this year, the National Biodiversity Manager for the Environment Agency, and is now an independent catchment restoration specialist.
As a result, he dealt with NFM long before it became fashionable.
“The simple truth is we are only scratching the surface with Natural Flood Management at the moment,” says Driver. “There is a lot more we can do, and a lot more we should be doing,” he says.
He sees one of the main problems is proving its effectiveness with scientific evidence, which is so important to tick the boxes on large-scale risk-based funding applications.
“With NFM it is quite difficult to demonstrate the direct connection between, say, restoring a blanket bog, or putting in 50 woody debris dams, and the reduction in flood risk in a city down stream,” says Driver.
“It is understandably hard to model that and to predict it.”
Driver thinks that momentum is moving in favour of NFM, and it is gaining support where it really matters, at the heart of the Environment Agency.
He believes it is this change in culture that is so important, which is why he lobbied – successfully as it turned out – for the ring-fenced funding for NFM announced by Environment Secretary Andrea Leadsom as part of the Autumn Statement.
“I felt if the Government was prepared to do that, it was a really strong signal to the flood authorities that we really believe there is mileage in this,” he says.
But for Sheffield, the spectre of those 2007 floods still loom large in the city’s consciousness.
The person charged with the responsibility of protecting it from further catastrophe is the council’s flood and water manager Jim Fletcher.
“Where is the surety?” asks Mr Fletcher, of natural flood management.
“We are committed to working with natural processes, but there is still absolutely going to be the need for infrastructure to protect this city from another 2007 event,” says Fletcher. “That event was extreme, but we were very close just this last Monday.
“The River Sheaf was eight inches away from overtopping. Had the storm continued beyond early evening, the River Sheaf would have overtopped. The railway station was very vulnerable on Monday.
“We cannot allow this to happen in Sheffield.”
Despite the fact that NFM was omitted from the recent public consultation on flood protection measures, he says there will be a public consultation at some stage in the future.
“We very much see the benefit of Natural Flood Management, but we see it as complementary,” says Fletcher. “We see it as more a medium to long term measure in order to negate climate change factors that are being predicted for Sheffield and for the country as a whole.”
“But I have to make sure this city is protected by 2021, which is the current investment period.
That is the council’s objective, that this city will be protected against another 2007 event by 2021.”
But Peter Worrall of the Don Rivers Trust believes that people’s attitudes are shifting. “I think the culture is changing,” he says.
“There is an expectation that flood risk will be managed in a way that is more natural.
“It is just common sense.”