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, protecting 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 - but 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. Our practical guide for farmers gives information on a range of measures including their purpose, where on the landscape to use them, the benefits to the landowner, an idea of costs and maintenance.

If you’re interested in implementing natural flood management measures on your land, visit the Natural flood management in Calderdale page for more information.

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 they grow and 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 Calderdale funded Hedge Fund 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. Compaction of soils, sometimes by animals, 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 greater infiltration of rainfall, reducing the amount of water travelling across the surface of a field and reducing soil erosion. 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.

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, promoting sustainable urban drainage and helping 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, helping to store more water, improve water quality and the 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 understory 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 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 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.

Lady watering plants with a watering can.

Sustainable drainage

Whilst the above techniques are mainly for landowners and farmers and could g oa 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 at home.

Making small changes such as green roofs, permeable paving, water butts, raised planters and attenuation ponds in our homes and gardens could result in a significant amount of water being temporarily stored during storm events in our urban areas. Find out more.

If you have a watercourse running through your garden or other land you also have responsibilities to manage flood risk.

Landowner standing next to a leaky dam made with large sticks.

Natural Flood Management in Calderdale

There are a number of projects across Calderdale designed to naturally manage flood risk. This interactive map shows completed and ongoing Natural Flood Management projects across the Calder catchment, detailing the types of interventions, funding sources and partnerships that have made this work possible. This spreadsheet summarises all of the information presented in the map.

Open up the map, then press the ‘Present’ arrow and allow the map presentation to fully load which, can take a couple of minutes depending on your internet speed. The orange hexagonal shapes at the top of the map explain how to move around the map and take a look at the project information presented.

View the map

Natural Flood Management Opportunities

While lots of work is already underway to naturally manage flood risk, there are a number of sites across the Calder Valley that would benefit from NFM initiatives.

The implementation of NFM measures can vary in terms of complexity, cost, and the benefits provided. This guide provides advice on the range of NFM measures available, the benefits provided and key information for landowners and farmers to consider which measures might be appropriate for their land. Information is also provided on the potential sources of grant funding available to help support the work.

This Natural Flood Management Opportunity map sets out the land areas where new NFM measures are likely to make the greatest impact for flood resilience and where ecological impacts are likely to be low, or where there may be some ecological constraints. The land across Calderdale is colour coded to show potential high-level opportunities based on our current ecological knowledge and catchments which have been prioritised through modelling.

Thinking about implementing NFM on your land? Get in touch for assistance and to hear about any funding opportunities that may be suitable: NFM@Calderdale.gov.uk.

To ensure we protect the biodiversity of Calderdale and don’t create flooding issues elsewhere, there are a number of steps that must be taken before NFM can be undertaken. This document explains these, and aims to assist landowner’s in the implementation of NFM upon their land. The NFM Project Officer is also available to assist landowners with any element of this, get in touch via: NFM@Calderdale.gov.uk.