How trees can stem flooding

Standing in a deep cutting where the river turns sharply back on itself, the banks high above our heads, it is hard to believe that this could flood. But it does, and frequently, drowning the fields above us.

At the moment, those fields – particularly the ones sandwiched within this wide loop of the river – are not used for much. There is unkempt grass, and the dry, sprouting tufts of weeds. But one day soon perhaps, under a new Forestry Commission scheme, the finger of land enclosed within this loop of river will become a wood.

The lower areas nearest to the river, which are most prone to flooding, could be planted with willow. On the higher land slightly further away there may be ash, oak and other traditional broadleaf species.

If the planting goes ahead, this little woodland – it would cover a bit more than ten hectares – would be one of a growing number appearing thanks to a Forestry Commission grant scheme.

It would certainly improve the appearance of the area, says Andrew MacDermott, the 23-year-old project officer from York whose job it is to persuade landowners to sign up for the scheme. “It would be lovely, with some trees here, and a footpath beside the river.”

But that is not why it would be planted. The main reason for having a wood here would be as a flood defence.

A woodland would not stop the waters rising and engulfing the fields immediately on either side of the river. But it would slow down the flow of the floodwaters: holding them longer and delaying their progress downriver – and ultimately their arrival in York.

If that saw peak flood flows coming down the Ouse from the Ure and the Swale arrived in York at a different time to the floodwaters coming from the Nidd, it could significantly reduce flood levels in York.

That, at least, is the theory. But how does it work?

It’s all to do with what Andrew calls ‘hydrological roughness’.

Fields like this do little to hold on to flood waters, he explains.

“When there is a flood, the water very easily flows off here. But if you plant trees here, say 1,200 or 1,600 per hectare, you get debris collecting underneath the trees. And this mass of debris, leaves and litter, means that the water has to go slower – which delays the peak flow downriver and eventually even in York.”

There are several ways that planting woodlands can help manage flood risk, according to a report by Samantha Broadmeadow and Tom Nisbet for Forest Research.

Trees reduce the amount of water that runs off from catchment areas into rivers and streams; they help the absorption of rainwater into the soil; and they delay the flow of floodwater downstream. They can also reduce the amount of soil and sediment washed into streams and rivers, so helping prevent soil erosion.

Admittedly it’s not easy to quantify all of this, Andrew says. There are many variables and it depends on the particular local circumstances of each flood area. “But the general idea is that planting trees will reduce flood levels.” The effect is small at first, but as the trees and woodlands mature it becomes much bigger.

So tree-planting isn’t a quick fix for Yorkshire’s flooding problems, Andrew admits, but it does offer a natural and long-term way to manage flood risk.

That is why the Forestry Commission has launched a grant scheme to encourage landowners in floodplain and water catchment areas to turn over land to new woodland.

The commission has done extensive modelling to try to identify the areas where tree-planting would have most effect on flooding.

There are three types of land they have identified that are eligible: floodplain, beside the Ouse and its tributaries such as the Nidd, and beside the Derwent, the Rye and the Seven; riparian land immediately next to rivers and streams; and wider catchment land, often on higher ground, from which water drains into small streams and becks, ultimately adding to the swell of flood waters.

The Forestry Commission has detailed maps showing exactly which parts of North Yorkshire are eligible for grant funding under the scheme. It aims to encourage the planting of 150 hectares of new woodland on eligible land over the next year, with a further 150 hectares the year after.

Landowners who take part in the scheme will be eligible both for Woodland Creation Grants of £1,800 per hectare, and forestry and flooding grants of £2,000 per hectare: a total of £3,800 per hectare. They will also receive annual grants to help manage the new woodland, worth from £60 per hectare for unimproved land to £300 per hectare for arable land.

It sounds like a lot of money, but for landowners, it is still a difficult decision to make, Andrew admits.

Land set aside for woodland cannot be used for anything else. While in the long term, the trees will be valuable crops – harvestable for fuel or timber – it will take many years for them to mature to the point where realistic income can be generated.

But the value of the woodland will steadily increase over the years, he points out – and it would be a real legacy to leave, especially on land that was not suitable for much else. As well as helping prevent floods, and offering landowners a future source of income from timber harvesting, the woods will be beautiful. “And they will provide habitats for wildlife too.”

ANDREW McDermott, the 23-year-old project officer whose job it is to persuade landowners to plant woodland under the scheme, comes from a family that has a historic connection with the countryside. Generations ago, he says, his family were farmers in Ireland.

He himself is a city boy, brought up in Fishergate, York. He went to St George’s RC Primary School, then Bootham School.

Before going to Harper Adams University in Shropshire to study countryside and environmental management, he took a year out, during which he worked as an assistant warden with the National Trust at Brimham Rocks.

He now works for Yorwoods, a publicly funded woodland initiative based at Ripon, which works with the Forestry Commission, local authorities and other public bodies to advise on woodland management and offer forestry training.

As project officer for the Forestry Commission’s Forestry and Flooding grant scheme it is his job to persuade landowners to apply for grants to plant woodland.

Part of that involves letting landowners who approach Yorwoods for advice on forestry management know about the scheme. But he is also being more proactive – and will, for example, be touting the grant scheme around at the Great Yorkshire Show.

He is keen to hear from any landowners in North Yorkshire who may be eligible for a grant.

Such land does not necessarily need to be near a big river to qualify, he stresses – because the scheme extends to higher land.

• To find out more about the scheme, phone Andrew MacDermott at Yorwoods on 01765 609355.

Pickering shows way

THE Forestry Commission’s Forestry and Flooding grant scheme is essentially an extension of an ongoing DEFRA-funded project in Pickering, Slowing The Flow, which effectively piloted methods of using tree-planting to manage flood risk.

The Slowing The Flow project began following the 2007 floods, which caused an estimated £2.1 billion of damage across Yorkshire and the Humber. “Climate change may increase the frequency of such floods, resulting in a major recurrent cost with significant implications for the regional economy and for affected communities,” a Forest Research report on the project said.

The Pickering Beck catchment area was identified as the ideal location in North Yorkshire to explore how land management and woodland planting could help reduce flood risk.

“Pickering has a long history of flooding and while a flood levitation scheme has been proposed in recent years, it is of too low a priority in terms of cost-benefit to be considered for approval,” the report said. “The town is particularly at risk from summer flash floods due to the steep nature of the catchment.”

The project included the Pickering Beck catchment area and that of the River Seven, which causes similar risk of summer floods in Sinnington.

Over the past two years, with funding from DEFRA, the Forestry Commission has been planting trees along streamsides and in the flood plain of the two catchment areas, and has also been restoring woody debris dams in small streams to help reduce and delay the flow of water off the hills and downstream.

That scheme helped develop and refine the techniques that are now being expanded, through the Forestry and Flooding grant scheme, across the whole area.

The key, however, is in the new mapping data the Forestry Commission has, which has enabled it to pinpoint fairly precisely the areas of land it feels would provide most benefit in terms of reducing flood risk.

It is these areas of land that are eligible for the grants.

Grants already made under the scheme include:

• £15,618 for four hectares (ten acres) of new woodland at Levisham Estate near Pickering

• £56,050 for 15 hectares (37.5 acres) at Skipster Hagg Farm near Pickering

• £4,446 for one hectare (2.5 acres) at Beacon Farm near Whitby

• £3,192 for one hectare (2.5 acres) at Gibralter Farm, near Hebden Bridge

• £17,024 for 4.5 hectares (11.25 acres) at Backstone Beck Wood, near Pateley Bridge