Slowing down

Taken mainly from the final report for the ‘Slowing the Flow’ Project

The ‘Slowing the flow’ project is now completed, ahead of approaching winter. The purpose of the project has been to reduce the risk and severity of flooding in Pickering and nearby Sinnington.

The approach has been to slow the flow of water from off the moors into Pickering Beck and the River Severn and subsequently down into the settlements below.

The last element has been the creation of a flood storage area at Newbridge, upstream of Pickering – a site to hold up, and so slow down, extreme flows of water. It can hold up to 120,000 m3.

The ‘Slowing the Flow’ project was one of a number of Defra pilot projects looking into reducing flood risk and impacts. The idea was to make the best use of natural processes by adapting land use and land management to slow down and delay the passage of water.

Phase 1 of the project concentrated on building up a working partnership including with the local community. The National Park Authority were heavily involved in Phase 1 of the project as a major landowner in the area. The National Park Authority owns Levisham Estate upstream of Pickering and a number of tributaries into Pickering Beck arise on the Estate’s moorland.

View of Hole of Horcum (part of Levisham Estate) - copyright Mike Kipling, NYMNPA

The land management work undertaken in the two sub-catchments included establishing no burn buffers along moorland watercourses to protect soils and retain vegetation, impeding moorland drains using heather bales to lessen erosion, constructing ‘woody debris dams’ which slow but don’t halt watercourse flow, creating riparian buffer zones in forestry, and large scale tree planting and long term woodland creation because trees prevent sediment runoff and hold and use more water than other habitats. Two timber bunds were also constructed in the River Severn catchment. 

Large woody debris dam during flood - from Forest Research: appendices to Phase 2 Final Report, May 2015

Large woody debris dam secured by angled posts and wire on Pickering Beck - from Forest Research: appendices to Phase 2 Final Report, May 2015Face of upstream timber bund within Forestry - from Forest Research: appendices to Phase 2 Final Report, May 2015Small woody debris dame - Horcum, Levisham Estate - NYMNPA

 

 

Heather bale 'check' dams within moorland drain - from Forest Research: appendices to Phase 2 Final Report, May 2015

Drainage channel - Fen Moor, Levisham Estate - NYMNPA

Slowing the Flow in action - Levisham Estate - NYMNPA

 

 

 

Slowing the Flow tree planting - Levisham Estate - NYMNPA

Phase 1 (2009 – 2011) led to Phase 2 (2011 – 2015) which allowed for the implementation of the outstanding land management interventions planned. One of the lessons learned was that five to six years is a more effective time scale for delivering a demonstration project, especially one that includes persuading landowners to change land use. Another lesson is that the measures undertaken have to be at an effective scale – the bigger the contribution to flood protection required, the larger and/or more extensive the measures need to be at the catchment level to make a difference.  The use of smaller, more diffuse, storage features can collectively contribute a sizeable flood storage volume, depending on their design and management – however catchment level planning/modelling is needed to guide and achieve the optimum placement and combination.

The ‘Slowing the Flow’ project was led by Forest Research, and the partnership that made it happen included the Forestry Commission, the Environment Agency, Natural England, North Yorkshire County Council, Ryedale District Council, the North Yorkshire Moors Railway, Durham University, Pickering Town Council and Sinnington Parish Council and the local community including vital landowners, and us. The project was possible only because of this joined up and inclusive approach to flood, water and land use management. Another lesson from the project is that efforts to reduce flood risk via land management interventions can be accidentally counteracted by other activities in the same catchment.

Although the main purpose of the project was to lessen the risk of flooding in Pickering, and also the village of Sinnington, the methods used will provide added benefits to biodiversity and the wider ecosystems. The piloting of the practical demonstrative measures have allowed the sharing of good practice, knowledge and skill development (e.g. NYMNP Apprentices).

Some issues…

Concerns over the stability of ‘woody debris dams’ and the potential for debris to wash out and damage downstream structures need to  allayed by the construction methods that use slot trenches and bracing logs to attach the structures to the banksides.

Having a National Park – a designated landscape – in the north of the sub-catchments had implications for the siting and design of land management interventions. For instance from a National Park point of view there was a limit on how much tree planting could be/should be accommodated on the Levisham Estate because of the ecological value of the existing moorland habitats which are designated as a Site of Special Scientific Interest and in some places also a Special Protection Area/Special Area of Conservation.

Persuading people to create woodland can be difficult. The selection of Pickering Beck as a demonstration sub-catchment was partly because of the relatively high level of public land ownership e.g. National Park, Forestry Commission. In the future achieving the necessary sizeable level of change on privately owned land is likely to require greater financial incentives. The new, integrated, Countryside Stewardship scheme should help by providing grant for planting that provides benefits, including reducing flood risk and diffuse pollution.

Conclusions…

Land management measures can make a significant contribution to downstream flood alleviation. They vary in type, size, scale of operation and mode of action but are most effective in combination as part of a whole catchment approach to managing flood risk. More modelling and experience of actual flood peaks is required to better understand the cumulative effect of the measures. In view of the level of commitment and investment required, resources are best focused on small to medium sized catchments that can be expected to deliver large-scale changes in land use and/or management.

It is not suggested that the ‘Slowing the Flow’ project will prevent all flooding in the two sub-catchments, but it is anticipated that there will be less flooding. It has been suggested that the previous 25% chance of flooding in any given year in Pickering, has now been reduced to a 4% chance or less…

Soggy moorland helping to stop soggy carpets

Rachel Pickering – Conservation Officer

I wish that my favourite view in the National Park was tucked away somewhere that nobody else knew about – but it isn’t.  Instead it’s one of our most photographed views – the Hole of Horcum within Levisham Estate. Not only is the view stunning but it has also proved to be a key location for landscape works towards the Slowing the Flow in Pickering project.

Work began on 8 January 2014 on the bund at Newbridge which will store flood waters upstream of Pickering. This work is a culmination of efforts by a number of partner organisations over the last few years to make changes to upstream land management to slow down the water running off the North York Moors and into Pickering Beck before it gets into Pickering town.  For the last three years the National Park Authority has been busy carrying out the following work on its own land at Levisham Estate.

Slowing the Flow - tree planting

Tree planting

Wooden dams created

Slowing the Flow - moorland gully blocking photo taken November 2012 - shows heather bales holding water back

Moorland gully blocking

  • The National Park Authority has spent £7,000 on partially blocking natural occurring moorland gullies with heather bales on various parts of the Estate.


Re-vegetation work

  • Heather brash has been spread in the Hole of Horcum to aid re-vegetation after the previous years’ bracken control left areas of bare ground.

Footpath repair work

  • An eroding footpath into the Hole of Horcum has recently been repaired with improved drainage that will slow down run off along the route.

Heather burning buffers

The hope is that with this type of beneficial land management established upstream of Pickering, along with the creation of the bund just to the north of the town, the chance of extreme flooding events will be lessened in the future.