A Natural Flood Management (NFM) scheme using ‘leaky dams’ on a stretch of the Medway near Tunbridge Wells, appears to have reduced the risk of flooding to more than 100 properties.
A report into the four-year NFM project by the South East Rivers Trust (SERT), has concluded that while Natural Flood Management is unlikely to stop flooding completely, it can alleviate the risk from less extreme events.
The project involved the installation of 105 Leaky Woody Structures (LWS) in 2019 on the Alder Stream catchment, located within the 900-acre Tudeley Woods reserve, owned by the Hadlow Estate. A total of 61 LWS were installed at Pembury Walks woodland.
The landowner worked with SERT to construct the ‘leaky dams’, which are made from timber sourced from the surrounding woodland – either from fallen trees or carefully selected over-mature conifers. Steep sided streams, known as ghylls, have logs jammed across them to create a network of strategically placed timber, to slow the flow of the stream. The process also involved filling smaller tributaries with brushwood which, over time, accumulates more sticks and debris to create a natural barrier.
Time lapse data and site observations revealed that the LWS were effective in backing-up and storing water, as well as slowing the flow, particularly in extreme weather.
Report author Tom Harrisson, Catchment Officer with SERT, said: “Projects such as Medway NFM have been pioneering in our region, by displaying the reduction to flood risk that is possible when working with multiple landowners across a whole catchment.
He added: “This particular project has also illustrated significant environmental benefits that NFM can provide.”
As well as helping to prevent flooding in around 100 properties downstream of Tudeley Woods, many of them in the villages of Five Oak Green and Capel, SERT identified that the use of LWS along the Alder Stream watercourse has protected the wet woodland habitat, retaining water for longer and helping to increase biodiversity.
The Alder Stream project was one of four on the Medway catchment, carried out between 2017 and 2021, and funded by the European Union Interreg North Sea FRAMES project and Defra, in partnership with the Environment Agency.
Harry Teacher, of the Hadlow Estate welcomed the findings of the report. He said: “NFM has become a key element of flood prevention in many parts of Britain and we are pleased to have been part of this pioneering scheme in the South East.”
SERT is now recommending further NFM projects are delivered in other flood risk areas to build on the momentum created by the Medway scheme. Find out more at southeastriverstrust.org.