Yarner Woods: Creating Storm-Like Conditions to Slow the River Bovey

A Protected Woodland With a Complicated Brief

Yarner Woods is both a SSSI and SAC, so the ecological constraints were significant.

Some trees could be used, while others had to be left alone because of their size, form, age, bat potential, or the presence of rare mosses and lichens. Yarner is particularly known for its lower plant interest, so this was not a case of simply selecting any tree that happened to be in the right place.

Trees to be retained were identified through a mixture of Natural England guidance, ecological constraints and on-site marking. Our team then worked carefully around those exclusions.

Dormouse mitigation also had to be followed throughout the project. This included pre-start briefings, marked constraints, careful working methods, avoiding unnecessary root disturbance, checking material before cutting or moving it, and keeping the team aware of how they were working through the woodland.

Yarner was also open to the public during the works, which added another practical layer. We had to manage walkers, dogs and public safety while carrying out chainsaw work, winching and watercourse operations in a woodland setting.

Working Methodically Up the Valley

We mobilised a four-person team led by our operations manager.

The team worked methodically from the lower part of our section of the valley upwards, using Stihl chainsaws, ropes, pulleys, wedges, slings, brushcutters, radios, first aid equipment and a 1.6t Tirfor winch.

The winch was a key part of the work. In places, trees were deliberately winched over to retain root plates and mimic windthrow. That sort of feature is valuable because it creates a much more natural disturbance than a clean cut stump. Root plates, torn ground, lodged timber and uneven brash all help change the way water moves through the site.

This was chainsaw work, winching and woodland judgement being used as a natural flood management tool.

Species worked with included alder, oak, willow, birch, holly and beech. Some trees were felled conventionally, while others were hinged, partially felled, winched, laid, left hung or positioned to create the right kind of obstruction and flow change.

These are not techniques we would usually use in domestic tree work, where the goal is normally control, tidiness and removal. Here, the point was different. The brief asked us to create controlled disorder.

Woody Structures, Deflectors and Floodplain Flow

Across our section, we installed approximately 45 woody structures and features.

Some acted like leaky dams. Others were better described as woody debris structures, brash features, deflectors or floodplain flow features. Not every feature was intended to do the same thing.

Some slowed water directly in the channel. Some pushed flow sideways. Some encouraged water to spill out onto the floodplain. Others created small pools, varied flow routes or roughness that would hold back debris and slow the speed of water in high rainfall.

Brash bundles were used for bank erosion repairs and to pack out some of the structures. Most of the material came from site, which was important. Using site-won timber and brash meant the features belonged to the woodland and avoided importing unnecessary materials into a sensitive site.

Cut holly and brash were mainly dragged into the features, while thicker stems were left in habitat piles where appropriate. No herbicide was used.

The holly understory was cut along the riverside and floodplain corridor to open up the woodland floor. In the longer term, that should allow more light into areas that had become heavily shaded, giving native ground flora more opportunity to return.

Making the Woodland Wetter and Messier in the Right Way

Good Natural Flood Management is not about blocking water. It is about slowing it, spreading it and giving it more opportunities to lose energy before it travels downstream.

At Yarner Woods, that meant allowing the watercourse to interact more with the surrounding floodplain.

Logs were positioned across channels and low areas. Brash was used to add roughness. Root plates and felled stems were left where they could interrupt flow. Deflectors were used to encourage water into side channels and wetter areas.

The finished work looked deliberately irregular, because that was the point. Straight lines and tidy banks rarely do much for a woodland watercourse. Natural systems work better when there is variation.

The intention was that during heavy rainfall, water would be slowed through the woodland, spread out into the floodplain, and held for longer within the site before continuing downstream towards Bovey Tracey.

Storm Bert Put the Work to the Test

Almost immediately after completion, Storm Bert arrived.

That gave the project the biggest possible test, much sooner than expected.

The results were visible straight away. Water slowed through the section we had worked on, spilling out into the floodplain and creating a series of side flows, pools and small channels through the woodland. The felled and winched trees remained in place, and the woody features began doing exactly what they had been installed to do.

It is always useful to see Natural Flood Management tested in real weather. A feature can look right when the water is low, but you only really understand it when a storm arrives.

In this case, the woodland responded well.