Slow with the flow

By Kathy O'Leary | 17 August 2020

Slow the flow and store more. That’s the essence of the Stroud Rural Sustainable Drainage (Rural SuDS) project in Gloucestershire, an innovative natural flood management project working to reduce flood risk and restore biodiversity throughout the catchment of the River Frome and its tributaries.

The project has been highlighted as an exemplary approach to tackling flooding in the Environment Agency’s National Flood and Coastal Erosion Risk Management Strategy for England (produced in July), which highlights the impacts of climate change and the need to create climate resilient places. What distinguishes it is its community-led approach and strong local, supportive partnership to manage the flow of water through the environment.

In June 2007, Stroud suffered badly from flooding when heavy rainfall rushed down the brooks and streams in the steep valleys leading into the River Frome, flooding homes and businesses. Described as an unprecedented and rare event, six weeks later it happened again.

Local residents were understandably angry and upset. Community Flood Action Groups were set up in the Slad and Painswick valleys, in the middle Frome at Chalford, and lower Frome at Bridgend and Eastington to campaign for better flood protection.

The Environment Agency had designated the Slad valley as at risk of destructive flash flooding, similar to the event that destroyed parts of Boscastle, Cornwall in 2004. A hard engineering solution – a concrete dam – was initially proposed in this most environmentally sensitive of landscapes in the Cotswolds Area of Outstanding Natural Beauty. Unviable, geologically unsuitable and unwanted by the residents of Stroud, this was not pursued.

Determined to find a better solution, local communities, championed by persistent and influential district and county councillors, worked with far-sighted individuals at the Environment Agency. The Environment Agency then commissioned a study to scope out a natural flood management proposal for the Frome catchment in 2012, following further disastrous flooding in Stroud that year.

The study achieved regional buy-in from district and county councillors from Painswick to downstream Bath, and acting on study findings, the Severn and Wye Regional Flood and Coastal Committee (RFCC) in 2014 agreed a three-year pilot to fund a project officer from the Local Levy Fund. A formal partnership between the RFCC, the Environment Agency, Gloucestershire CC and Stroud DC was established and under a collaborative agreement, the district council agreed to employ a project officer based at its offices at Ebley Mill, next to the River Frome, to implement and promote rural sustainable drainage in the Frome catchment.

The project officer built relationships with local communities, landowners and their contractors, encouraging them to take ownership and responsibility, and to design and construct natural flood management measures on their own land.

The measures deployed broadly fall into three categories, the first of which is slowing the flow by increasing resistance through planting flood plain or riverside woods or constructing dams of large woody debris in channels and gulleys or on flood plains. Leaving or placing fallen trees and adding further woody debris to create ‘leaky dams’ can be beneficial, changing the shape of the channel and pushing flows onto the bank to create pools and riffles which provide a variety of habitats for fish and aquatic insects, attracting mammals and birds to feed on them.

The second category of measures is attenuating water, using and maintaining the capacity of ponds, ditches, embanked reservoirs, channels or land to store more in the event of heavy rainfall. The third is to slow the flow by increasing soil infiltration, allowing water to soak away through free-draining soil to reduce surface run-off. Combined, the measures reduce the flood peak and delay its arrival downstream by restricting the progress of water through a catchment, working with natural processes. This gives downstream communities more time to prepare.

So far the Stroud Rural SuDS Project has worked in partnership with 42 different landowners, including the National Trust and Gloucestershire Wildlife Trust, whose volunteers have also worked on a significant number of the 559 natural flood interventions implemented. Other key partners include the Wildfowl and Wetlands Trust and the University of Gloucestershire. More than 1,500 trees have been planted and some 26,390 metres of riverine length enhanced, resulting in improved habitat, biodiversity and water quality. The project has also engaged 2,500 people through talks, workshops, conferences and project site tours.

The early impact of the project showed when in the 2015-16 winter floods, peak flood level at the Slad Road gauge in Stroud was reduced by up to 1.4m and fewer homes and properties were flooded. The RFCC agreed funding for the project officer for a further three years, and the partnership is now working to secure funding for the next six years from the RFCC, to build on the success it has already achieved and improve climate resilience in the years ahead.

Kathy O’Leary is chief executive of Stroud DC

Preparing for the storms ahead

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