New earth bunds, scrapes and leaky dams have been popping up in the Purbeck countryside as part of a scheme to reduce the flooding risk along the Swan Brook, which flows down to the sea at Swanage in Dorset.
The first phase of work, funded by a £325,000 grant from the Environment Agency, has just been completed by the National Trust, and an update on the project will be discussed at a Swanage Streams Partnership meeting, hosted by Planet Purbeck at 7.15 pm on Wednesday 26th November 2025 at The Swanage School.
The areas circled in yellow where natural flood management measures have been introduced in Purbeck
Slowing the flow of rain water
The heads of the river scheme is aimed at slowing the flow of rain water from the hill sides and fields, along the ditches, and into the local river network, giving the Swan Brook, which is classified as being in ‘poor’ condition, more time to cope with the volume of water when a sudden downpour happens.
And rather than using concrete man made features, the project is using natural flood management techniques like building low earth bunds which are similar to embankments, creating scrapes which are shallow seasonal ponds, and placing tree trunks across ditches to create leaky dams.
The various interventions don’t change the direction of flow, or prevent flooding altogether, but are intended to spread water across the natural floodplain.
A leaky dam made from old tree trunks slows down the flow of rainwater in a ditch
Project officer Ben Cooke with the tree trunks put in place to slow the water run off coming down the hillside at Spyway
“Hold water then gradually release it”
National Trust’s project officer for rivers and coast Ben Cooke, who will be speaking at the Swanage Streams event, said:
“We are using various methods to hold water then gradually release it as it runs off the hillsides. The aim is to prevent storm water from careering down towards Swanage.
“It’s a more natural way of flood management, replicating obstructions in rivers caused by falling trees or, of course, the eco-engineering done by beavers.”
A newly created scrape and a bund slowing the water heading towards Langton Matravers
After rainfall, the scrape temporarily holds the water, allowing it to soak away gradually
Monitoring the measures
The six sites in Purbeck where the natural flood management measures have been installed are on National Trust tenanted farmland at the headwaters of tributaries that feed into the Swan Brook.
The farms taking part in the innovative scheme are Westwood Farm, Spyway Farm, Godlingston Manor Farm, and land in Langton Matravers.
To work out how effective the measures are over winter 2025/6, monitoring devices have been installed to record the water levels and flow rates.
In addition, local residents are being asked to help monitor what is working and what could be improved by recording video or taking photos during or after periods of heavy rainfall and sending them to the National Trust.
However early indications of how the natural flood management techniques are working are encouraging.
The level of the leaky dam is kept much lower than the ditch to prevent it from overflowing
Not an unusual gymkhana course at Spyway but an attempt to spread out water running down the hill over a wider area and slow it down
“I’m sure it will help reduce flooding downstream”
Paul Loudoun, a farm tenant in Langton Matravers, said:
“I’m very pleased to help by having flood relief measures like the attenuation ponds on my land. It’s vital that we direct this life-giving resource to a place of benefit and so help nature create new habitats.
“After just a few heavy showers, the system is working and I’m sure it will help reduce flooding downstream when it gets really wet in January and February.”
A scrape, like this one at Godlingston, can create a new habitat for wildlife
“Already attracting birds”
As well as reducing the flood risk, the measures retain water in areas longer, helping to counteract the effect of dry summers.
It also filters run off from fields, and creates habitats for a range of wildlife, from dragonflies and aquatic insects to migrating birds.
Ben Bowerman of Godlingston Manor Farm, said:
“We are long-term tenants of the National Trust and work in partnership with them towards an overall goal of nature conservation. The scrapes created for this project are already attracting birds, so we look forward to seeing how they develop as wildlife habitats.
“Farming has changed since my father started here in 1949, and my son’s future will be finding ways to work the land not just for food, but also for nature restoration.”
A bridge has been built at Spyway to allow walkers to cross the field during periods of heavy rainfall despite the widening of the flood plain
The cows are clearly not bothered about the new and unusual features in their field!
“Just the beginning of widespread adoption”
Footpath routes have been considered as part of the project. On one of the flood plains near Langton Matravers, a culverted wooden crossing has been built, so walkers can still use the footpath when the groundwater is high.
Ben Cooke added:
“Individually, each of these nature-based flood mitigation measures may not seem like much. However, they all form part of the jigsaw puzzle that when put together can benefit people, properties and wildlife.
“We hope this is just the beginning of widespread adoption of these types of nature-based solutions, throughout our rural and urban landscapes.
“Natural flood management techniques need not be restricted to National Trust land in Purbeck – other landowners can deploy these relatively cheap measures and there are grants available.
“And of course anyone with a garden can think about installing a waterbutt, digging a pond, planting trees, and avoiding too much impermeable landscaping. It all positively contributes just as much as the work we’re doing on the National Trust land.
The Swan Brook may start in the Purbeck countryside but flows through Swanage’s town centre…
…before heading out to sea by The Mowlem
Swanage Streams Partnership event
The Swanage Streams Partnership, which includes the National Trust, Dorset National Landscape, Planet Purbeck and Swanage Town Council, was launched in November 2024. It was formed to improve the condition of the Swan Brook and the other local streams.
At the public meeting at 7.15 pm on Wednesday 26th November 2025 at The Swanage School, speakers will include:
- Nick Reed – Retired Environment Agency officer and Swanage streams expert
- Ben Cooke – National Trust rivers and coast project officer
- David Brown – National Trust land and nature programme manager
- Culvin Milmer – Swanage Town Council
- Luke M Luke and Peter Floyd – Planet Purbeck
Everyone is welcome to attend the event, which will not only update on the progress of the project but also look forward to future events.
Further information
- Anyone who would like to help with the project by photographing or videoing the flood measures during or after heavy rainfall, should email purbeck@nationaltrust.org.uk
- More about the Swanage Streams Partnership
