Slowing the Flow at Pickering

Slowing the Flow at Pickering is a Defra pilot project exploring how natural measures can help manage flooding. It features a number of innovative, cost effective techniques for storing more water in the landscape and reducing its rate of flow downstream.

Slowing the Flow at Pickering uses natural measures to control floodwaters – such as large woody debris (LWD) dams.
Slowing the Flow at Pickering uses natural measures to control floodwaters – such as large woody debris (LWD) dams.

Slowing the Flow at Pickering is exploring a new approach to flood management. Situated in North Yorkshire, England – across the catchments of Pickering Beck and the River Seven – the project is about working with nature to try and store more water in the landscape and slow its passage downstream. Whilst this will not prevent all flooding, it is expected to reduce the frequency of future floods in the towns of Pickering and Sinnington, as well as deliver a range of other benefits to the local environment and community.

Project Details

Location: Pickering, North Yorkshire, England
Cost: £3.2m
Date of completion: Ongoing/long-term demonstration study
Client: Department for Environment, Food and Rural Affairs (Defra)
Main Contractor: Forest Research
Project manager: The Slowing The Flow Partnership Board
Challenge summary: Pitt review recommendation 2007: deliver flood risk management involving greater work with natural processes
Challenge solution: catchment management approach incorporating natural measures and traditional flood storage

Need for the Scheme

Sir Michael Pitt's review of the devastating UK floods of 2007 made 92 recommendations for improving flood risk management, including specific measures to implement partnership approaches and better "working with nature" processes. In response, Defra commissioned three pilot schemes at Holnicote, Kinder Scout and Pickering. The Pickering project was initiated in April 2009 with a clear brief to demonstrate how the integrated application of a range of land management interventions can help reduce flood risk at the catchment scale, as well as provide wider multiple benefits for local communities.

The town of Pickering is situated in North Yorkshire, England. Pickering Beck flows through the town, fed from the North Yorkshire Moors in the higher ground to the north. Adjacent to the Pickering Beck catchment is that of the River Seven, which flows through the town of Sinnington.

Pickering and Sinnington both have long standing issues with flooding. Pickering flooded four times between 1999 and 2007, the last of which caused around £7m damage to homes and businesses. Proposals were made for a flood alleviation capital scheme in the town, but cost-benefit analysis showed plans to be unaffordable when set against national cost-benefit thresholds and other priorities.

Instead, a catchment level land management approach was devised to deliver improved flood protection through "working with nature" processes. A crucial element of the approach was to better understand how floods are generated in a catchment and how land use and management affects the speed and volume of flood flows (four principal land use types were identified in the Pickering catchment – forest, arable, heather moorland and improved grassland).

Slowing the Flow at Pickering is a partnership project. It is led by Forest Research, closely supported by Forestry Commission England, The Environment Agency, The North York Moors National Park Authority, Durham University, Natural England, Local Authorities and the wider community. The lead funder is Defra. Representatives of all partner organisations formed the Slowing the Flow Partnership Board.

A total of 19ha of riparian woodland was planted within the Pickering Beck catchment
A total of 19ha of riparian woodland was planted within the Pickering Beck catchment

Design & Construction

At the core of the whole-catchment approach at Pickering is the implementation and evaluation of a number of land management interventions to help slow down and reduce flood flows. By attenuating flow upstream, water flow can pass through Pickering within an identified safe conveyance level, alleviating pressure at major pinch points such as at the Ropery Bridge. Across the scheme, most intervention measures were targeted at the Pickering Beck catchment though some extend into the neighbouring River Seven catchment, helping to manage flood risk to Sinnington.

The solution for the site involved two main strands – natural catchment measures and traditional floodplain storage.

The natural catchment measures strand of the project was led by the Forestry Commission. Through detailed "opportunity mapping" by Forest Research and hydrological/hydraulic modelling by the University of Durham, a number of locations were identified within both the Pickering and Seven catchments which could deliver positive impact by reconnecting the water course with its flood plain, and consequently slow the flow of water downstream. The range of interventions applied include:

  • Construction of large woody debris (LWD) dams – a total of 129 timber dams were constructed in the upper catchment area of Pickering Beck. The dams consist of a "leaky" framework of logs and branches that straddle the water course, secured in place by wedging and wiring the logs to bankside stumps or posts. At just £55-500 each to build, depending on size, they represent a relatively cheap and sustainable option for flood storage. The leaky nature of the dams also means that passage of fish is unaffected.
  • Construction of timber bunds – a bigger version of the LWD dams. Two were constructed in the River Seven catchment as part of a trial, at 16.5m wide and 57.5m wide, each with a 1.5m high wall of stacked logs across the full width of the floodplain to form a leaky bund.
Central part of one of the two experimental timber bunds in the River Seven catchment
Central part of one of the two experimental timber bunds in the River Seven catchment
  • Blocking moorland drains and controlling erosion – three moorland drains identified as discharging too much run off were blocked. Nearly 200 small check dams were assembled using heather bales, helping to alleviate run off from other drainage points. Reseeding of other sites and repair of footpaths also helped reduce run off.
  • Establishing no-burn buffer zones – heather burning can exacerbate surface run off by reducing roughness of soil and increasing its hydrophobicity. Ten-metre zones were established alongside watercourses to protect riparian vegetation and soils.
  • Planting riparian and floodplain woodland – this technique can be effective by increasing channel and floodplain hydraulic roughness, delaying flood flows and raising upstream water levels (i.e. flood storage). A total of 19ha of riparian woodland was planted within the Pickering Beck catchment and 10ha in the River Seven.
  • Planting farm woodland – land use for farming, both arable and livestock, can lead to increased run off through compaction of soil, whereas woodland planting increases soil infiltration and water evaporation. A total of 15ha of farm woodland was planted in the River Seven catchment.
  • Farm scale measures – examples include installing sediment ponds, swales and check dams, cross drains on tracks and small scale storage. This approach involved close engagement with farmers and advising them of grant support on offer to implement such measures.

The Environment Agency led the more traditional flood storage approach. After extensive investigation, a suitable site was found for construction of a bund (a large raised reservoir) 2km upstream from Pickering village.

Bund (large raised reservoir) providing flood storage, situated at Newbridge
Bund (large raised reservoir) providing flood storage, situated at Newbridge

Designed by Arup, the reservoir has a capacity of 120,000m3 and features 1km of embankment split into two sections: a spillway 2m above natural ground level and a lateral embankment protecting the adjacent North York Moors railway. A concrete control structure positioned in the centre of the reservoir restricts the flow of water downstream to Pickering to the target safe conveyance rate of 14.5m3/s.

Benefits Delivered

Outcomes and benefits of the Slowing the Flow project include:

  • Risk of flooding in the town of Pickering reduced from a 25% chance in any year to less than 4%
  • A strong and enthused local partnership in place to take the project forward, by maintaining the implemented measures and seeking opportunities to extend them to further reduce the risk of flooding in Pickering and Sinnington
  • An engaged local community, who have embraced the concept of working with natural processes and have faith that this approach makes a positive difference to flood risk management – the scheme having performed successfully already during high rainfall events in 2012 and 2015
  • A much more joined up and inclusive approach to flood, water and land use management, driven by stronger local and regional delivery partnerships
  • Greater national awareness and consideration of the benefits of working with natural processes, e.g. through strong brand recognition of "Slowing the Flow"
  • Positive influence on Government policy and support for woodland creation
  • Raised awareness of the multiple benefits/services provided by working with natural processes and informed better economic evaluation of ecosystem services

Further Information

Slowing the Flow at Pickering featured at ICE Flooding 2016. Tom Nisbet, Head of Physical Environment Research at Forest Research, presented an in depth view of the project, covering:

  • Background on Defra pilot project and description of catchment approach
  • Technical details of project measures, including cost-benefit
  • How the project measures performed during Boxing Day 2015 flood

Further details and updates on the continuing research at the site are available at www.forestry.gov.uk/fr/slowingtheflow.

Interested in seeing your project featured?

Do you or your company have a project you'd like to share with civil engineers from across the globe?

Our Knowledge Marketing team sources content from across the world of civil engineering, as well of as offering opportunities for sponsorship.

Training opportunities from ICE

ICE provides world class training for civil engineers looking to develop their skill set.