Natural Flood Management - Eye on Calderdale

A Calderdale field full of trees that have just been planted

What is natural flood management?

The Calderdale landscape means that rainwater can flow rapidly down the hillsides into our valleys causing flooding to occur. This can happen in a summer thunderstorm when the ground is dry and hard or, more often, after a long period of wet weather when the ground is already very wet. Natural flood management works to naturally hold or slow the flow of water during periods of heavy or persistent rain. This helps to protect the towns and villages below.

Natural flood management complements the flood defence engineering work that is happening across Calderdale. Depending on the measures taken it can deliver other environmental benefits too, including:

Providing habitat for wildlife
Filtering water entering the river and acquifers
Helping to store carbon

It is an evolving area of work nationally, regionally and locally. It is particularly developed in Calderdale where our unique geography makes us susceptible to very rapid flood events as water runs off the hills.

Tree surrounded by beautiful blue skies.

How does it work?

Anyone with land can implement natural flood management measures. This could include anything from planting trees or a hedge to changing the way farmland and moorland is managed so that it absorbs more water.

If you’re interested in implementing natural flood management measures on your land, visit the Natural flood management in Calderdale page for more information. Here, you'll find our practical guide for farmers which provides information on:

The range of NFM measures and their purpose
Where on the landscape to use them
The benefits to the landowner
An idea of costs and maintenance

There are a range of opportunities to fund Natural Flood Management projects. This page introduces a few of the available options.

Looking straight into the plastic where the tree saplings is growing.

Tree planting and hedgerows

Planting trees helps to prevent flooding by:

Slowing rain reaching the ground
Absorbing water as the trees grow
Helping water to infiltrate the ground

Several large tree planting projects have been completed in Calderdale. Others are underway that will see thousands of new trees being planted.

Treesponsibility has planted an average of 5 hectares of new woodland per year in Calderdale over the last 25 years. Hundreds of people from all walks of life, schools, community groups and visitors, have been involved with tree planting projects of all sizes.

The Hedge Fund project is working with schools and landowners to encourage planting of hedgerows across the landscape. Work with Leeds University has modelled how hedgerows could have a significant impact on slowing water flows down hills.

Farmer stood at the edge of the empty attenuation pond whilst tending to her sheep.

Improving soils

A number of techniques can be used to improve soils to allow more water to penetrate the ground and be held by the soil. Soil can become compact, sometimes as a result of animals, which can lead to more water flowing across the land into rivers.

By aerating their land, landowners can help reduce flooding downstream. Aeration of grassland allows rainfall to filter through, reducing the amount of water travelling across the surface of a field. There are other benefits to soil aeration too:

Allowing air to get to the grass roots and soil
Helping root development
Alleviating compaction
Reducing slurry and fertiliser runoff

The Calder & Colne Rivers Trust are working with a network of South Pennine farmers to promote good farming practice such as soil aeration to help hold more water on the land.

A landscape view of a landowner standing next to a leaky dam.

Slowing surface water runoff

Using our unique landscape in innovative ways can help to slow the volume of water coming down our hillsides. Attenuation basins, similar to big ponds, store large quantities of water which slowly empty once the rain has passed. Leaky woody dams mimic natural water management by providing small amounts of temporary water storage.

Local charity, Slow the Flow Calderdale, run regular volunteer days building leaky dams at Hardcastle Crags. They also promote sustainable drainage and help to raise awareness of NFM. Techniques such as fascines and bundles of sticks on slopes help other vegetation establish, reduce soil loss and slow water runoff.

Panoramic view of Calder Valley. Rolling hills with mist sitting in the valley bottom.

Restoring our moorland

Moorland in good condition is covered in plants such as sphagnum rich blanket bog which is peat forming. This absorbs water and slows the flow of water into our valleys. Peat and moorland covers close to 35% of the total Calder catchment area. Conservation and restoration of this upland habitat is an important, ongoing and long-term commitment because of the benefits to wildlife and people.

Moors for the Future and Yorkshire Water have been carrying out large scale moorland restoration across the South Pennines for many years. This has helped to:

Store more water
Improve water quality
Boost biodiversity of the moorland

Woodland management

Active woodland management includes careful, selective removal of some trees to allow more light to the woodland floor.

Enabling more plant life to grow underneath trees helps to ‘roughen’ up the woodland floor. This creates a number of benefits, including:

Slowing the flow of rainfall
Temporary ponding
Increasing rainfall infiltration to the soil
Supporting improved biodiversity

Woodland management in action is very visible at Hardcastle Crags where the National Trust are actively delivering on NFM.

Whilst trees generally protect against erosion, beech trees are a particular challenge. They shade out the forest floor and are shallow rooted, which can present an erosion risk on steep valley sides. As a result, selective felling of beech trees is sometimes necessary, allowing the forest floor to revegetate and slow down water passing downhill.

Rolling hills in the Calderdale Valley. A large reservoir can be seen in the distance.

Reservoir management

Yorkshire Water is currently evaluating the success of recent trials to investigate using reservoirs above Hebden Bridge to store water and help reduce flood risk. These trials involved reducing the levels of the reservoirs to allow for the storage of flood water. This will help to determine whether this is feasible in the long-term. Visit our Reservoirs page to learn more about this project.

Lady watering plants with a watering can.

Sustainable drainage

While the above techniques are mainly for landowners and farmers and go 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.

Making small changes at home could result in a significant amount of water being temporarily stored during storm events in our urban areas. Measures include:

Green roofs
Permeable paving
Water butts
Raised planters
Attenuation ponds in our homes and gardens

Visit our sustainable drainage page to learn more about the simple changes you can make to your property can help to minimise flooding. If you have a watercourse running through your garden or other land you also have responsibilities to manage flood risk.