How are NFM techniques being used to alleviate flood risk in Calderdale?
Since its formation in 1998, Treesponsibility has planted an average of 5 hectares every year – that’s over 12 acres of new woodland per year. The new woodlands will help to reduce the risk of flooding by increasing the capacity of soils to absorb water during heavy rainfall, improving infiltration, intercepting rainfall in the canopy and helping stabilise hillsides.
Hundreds of people from all walks of life have been involved with the project, including local volunteers and landowners, schools from Calderdale and beyond, a wide range of community groups, and visitors from further afield joining them for their tree planting weekends.
They are always looking for new volunteers to help them achieve their ambitious tree planting targets, so call volunteer coordinator Christina on 07709 690368 or email firstname.lastname@example.org if you would like to get involved. More information can be found on www.treesponsibility.com.
Of course, the responsibility to plant trees and protect existing ones does not belong solely to Treesponsibility, and all projects and new developments should be mindful of the need to include/retain trees.
Blanket bog restoration
MoorLIFE 2020 is a 5 year project that aims to protect remaining active blanket bog in the South Pennines Special Area of Conservation, hosted and managed by the Peak District National Park and delivered by the Peak District National Park Authority, National Trust, RSPB and Pennine Prospects.
The moorland blanket bog habitat that surrounds Calderdale is rarer than rainforest, and home to unique plants and animals. It’s where our drinking water comes from too. Special bog moss helps to slow down the flow of rainwater when it falls, reducing the risk of flooding in the local area.
Conservation works to protect blanket bog in the South Pennines SAC include bare peat stabilisation works, raising water tables and improving water quality by blocking erosion gullies, re-introducing native shrubs, managing invasive species, and increasing the diversity of and amount of Sphagnum moss.
More information on the project is available at www.moorsforthefuture.org.uk/moorlife2020. If you would be interested in volunteering with Moors for the Future, you can find out about their current roles here.
Slowing surface water runoff
Slow the Flow Calderdale (STFC) was set up to look scientifically at the issue of why and how the Calder Valley floods and to look at natural flood prevention measures and solutions to slow the volume of water which comes down the hillsides into the River Calder, thereby reducing the flood peak and limiting out of bank flow where it matters, in our towns and villages.
This can be done using rural interventions such as leaky woody dams, plate weirs, tree planting and attenuation ponds, and urban measures such as swales, green roofs, permeable paving, and rain gardens.
They are currently working on a pilot project with the National Trust at Hardcastle Crags. Early indications are that the leaky dams there are working to slow the flow and reducing the impact of flood water finding its way down the Calder Valley. STFC are attempting to scientifically monitor their interventions, and are working with dissertation students from Leeds Beckett University. They hope to publish results during 2018 that will help towards a growing evidence base for the benefits of this type of NFM approach.
They are also working with partners to identify other areas which would benefit from the installation of leaky dams, so if you know of such an area, please get in touch. Information on upcoming volunteer days can be found on http://slowtheflow.net.
River and canal improvements
A number of local and national organisations work hard to conserve our waterways with a view to protecting plants and wildlife, improving water quality and increasing flood resilience. This includes measuring the health of the river by monitoring wildlife, water quality and pollution, removing litter, debris and vegetation from the waterways and controlling invasive plants to protect native species.
Calder Future (part of Calderdale Sustainability Forum) is a partnership between the local community and agencies that have responsibility for waterways within the Calder Valley, which was formed to bring a coordinated approach to river and canal improvements.
As part of this work it has joined forces with Calderdale Council and the Environment Agency on a river stewardship scheme which aims to involve local people and businesses in the clearing of waterways.
You can learn more about Calder Future’s activities and find out how to get involved at http://calderfuture.org.uk.
In addition, the Calder Rivers Trust runs a River Health project which has trained dozens of volunteers to monitor the invertebrate life in our rivers to investigate changes in water quality. They are also active in improving river habitat by removing barriers to fish passage with the ultimate goal of allowing migratory fish such as salmon to return to the Calder. To find out more about their work or to get involved, visit www.calderandcolneriverstrust.org.
It is important to carry out prompt action to deal with and stabilise landslips after a flooding event before further rainfall transports the soil into the drainage systems below. Since the Boxing Day Floods, Environment Agency funding to the SOURCE partnership has paid for the treatment of nine landslips at six locations.
The work has been carried out by BlackBark and Sticks And Stones using brash from woodland management – this is an ideal resource for erosion control as it can be processed into tight bundles called fascines which are then pegged into the ground across the contour to stabilise the soils.
The partnership is always on the lookout for new sites to treat, so if you have a site that could benefit from fascines or know a landowner with such a site then please arrange a visit by contacting email@example.com
Whilst trees generally protect against erosion, beech trees are different because they shade out the understory and are shallow rooted, which can present an erosion risk on steep valley sides. EA funding has paid for selective felling of beech at Brown Bottom Farm and Hebden Hey.
Similarly, Himalayan Balsam is an annual plant which out-competes native perennials, resulting in bare soils in winter months. The SOURCE Partnership has put effort into balsam eradication in Colden Clough – a programme that will be continued in the next few years.
Yorkshire Water is currently evaluating the success of a recent trial involving a change in how it manages its reservoirs in the Hebden Bridge catchment to help reduce flood risk in the area.
This trial involved reducing the levels of the reservoirs above Hebden Bridge to allow for the storage of flood water. This will help them to understand whether this is feasible and whether a longer-term change to reservoir management is possible.
To help keep the reservoirs lower, they increased the flows in to the aqueduct to Albert Water Treatment Works in Halifax so the water could be treated and put into supply. Not all the excess water was able to go into supply as they still needed to take water from other reservoirs in the area so they needed to put more water into the downstream watercourse.
These reservoirs already provide compensation flows into the downstream becks for environmental reasons and Yorkshire Water needed to alter these flows, so this change was advertised with the Environment Agency before the trial to allow interested stakeholders to comment on the proposals.
More information on the trial can be found at www.yorkshirewater.com/hebdenbridgereservoirs.
Millponds and swales
Two recent projects have taken place to optimise existing bodies of water for flood water storage.
An abandoned mill pond at Stone Booth Cottage in Crimsworth Dean has been restored and modified so that it can attenuate up to approximately 1500 m3 of water during a storm event. The pond had silted up over the years and the restoration required around 1000 m3 of silt to be dredged out and encapsulated in a nearby excavation.
The feature has been landscaped and should return to its natural state within around two years.
Over at Tipside, the Todmorden Riverside Improvement Group has been working to protect and manage a biodiverse area of open space in the town centre for people and wildlife since 1998. Tipside is already a flood zone, lying immediately alongside the Calder, with bunds at either end, installed by the Environment Agency.
The latest project has been to construct a shallow swale on a particularly wet bit of the site to create a new wetland habitat, prevent water ponding on the existing footpath, and help to slow the flow by taking some surplus water during wet periods. Read more here.
Urban Sustainable Drainage Systems (SuDS)
While the above initiatives are going a long way towards improving Calderdale’s flood resilience, there are a number of ways that members of the community can contribute on an individual level and Slow The Flow: Calderdale’s ‘You Can Slow The Flow’ project helps to explain how.
Placing small interventions such as green roofs, permeable paving, leaky water butts, raised planters and attenuation ponds in our homes and gardens, businesses, schools and public spaces could result in a significant amount of water being temporarily stored during storm events in our urban areas.
This could help to reduce peak flows which, together with catchment management and traditional flood defences, would contribute to reducing the scale and damaging effects of flood events. You can find out how you can slow the flow here.
Urban Sustainable Drainage Systems (SuDS) complement rural NFM measures by mimicking the natural water cycle, thereby retaining water where it lands (instead of shedding it quickly to drains and watercourses, which can lead to floods).
Calderdale Council is currently revising its drainage design guidance for developers for flood risk purposes, including the use of sustainable drainage systems (SuDS).