Boxing Day 2015 saw one of the most significant natural disasters in the Calder Valley in hundreds of years: a huge flood event. It stretched from the very start of the River Calder at Walsden, on the edge of Lancashire, right through to Brighouse, and Wakefield, affecting thousands of residents, homes and businesses.
In 24 hours, between 60–100mm of rain fell on already saturated ground, which meant the rain had nowhere left to go, so it submerged roads, towns and villages along the Calder Valley. Flood water affected 4,000 homes and 2,000 businesses. For many people, life was never quite the same again.
The Calder Valley, with its steep-sided valleys, is a ‘rapid response’ catchment, one that responds rapidly to large amounts of rainwater cascading down steep sided valleys, resulting in rapidly rising flood waters in the valley below. This resulted in all the excess water accumulating in one small area all at once. Typical river levels at Mytholmroyd are usually between 0.4m–2.7m, but on Boxing Day 2015, the levels reached 5.74m which resulted in extremely significant flooding. In Hebden Bridge, the river level hit around 3.31m, setting an unwelcome new record in this very vulnerable town.
Many householders and businesses lost everything to the flood water, with water rising as high as 2m above street level in places. Everything was polluted with raw sewage as the flood water dominated the low-lying valley towns and villages. Beyond the obvious physical damage, the floods triggered long-lasting impacts on mental health, housing security, insurance access and the viability of local businesses.
The Boxing Day aftermath
In the days following Boxing Day, and for many subsequent weeks, the incredible community came out in force to help friends and neighbours. The local authority set up several flood hubs to co-ordinate the relief effort to help residents and businesses deal with the after-effects of this disaster.
The Calder Valley appeared in the media for days after, as the relief effort took hold and many millions of pounds were raised by The Community Foundation for Calderdale (CFFC). The CFFC distributed this money to homes and businesses to enable them to recover. Volunteers from around the UK arrived to help, and donated their time along with providing cleaning materials, kitchen appliances, beds, furniture as well as fresh and hot food.
It became apparent that flooding was now to become a more frequent feature, not just in Yorkshire but in the UK and around the world. Climate change suddenly became real and tangible for many people for the first time.
The birth of Slow The Flow
From out of this mayhem, Stuart Bradshaw, a local Hebden Bridge resident and a civil and structural engineer, decided to try to find out more about why communities flood, and to explore some simple solutions that might help deal with such a huge challenge. An initial, small group of likeminded local people – landscape architects and engineers, communication specialists and educators – came together and formed the catchily titled ‘Calder Catchment Flood Studies Network’ (CCFSN). They wanted to look at what could be achieved on a local level, and to figure out if, by working with nature, they could implement simple solutions for the Calder Valley and for communities around the UK. They knew they had the professional skills and enthusiasm to offer, without being hindered by the red tape faced by government organisations trying to co-ordinate ‘top-down’ solutions. (This theory was borne out by the fact that, a decade later, the Environment Agency’s ‘hard engineered’ Flood Alleviation Scheme (FAS) for Hebden Bridge has still not commenced).
The group started by measuring and assessing the rivers and tributaries along the Calder Valley to understand the capacity of the river network. It soon became clear that the challenge was to slow the rainwater and runoff from the hills and, in so doing, reduce the peak of the flood in the densely populated valleys below.
Slow The Flow was a focused group born out of the CCFSN in the summer of 2016; becoming constituted in late 2016 when it started looking for funding and land to work on to slow the flow!
The Environment Agency was offering funding for Natural Flood Management (NFM) projects that could lead the way in demonstrating what is possible. However, as a newly-formed voluntary group, Slow The Flow did not have its own land, or a bank account and constitution large enough to apply by itself. As one of the biggest landowners in the country, and with a prominent and well-loved site just above Hebden Bridge, The National Trust (NT) offered to partner with Slow The Flow. The NT granted permission for Slow The Flow to use their land at Hardcastle Crags, and were wonderfully supportive as Slow The Flow developed its flagship pilot NFM project.
Innovation on a local level
Hardcastle Crags is a large and beautiful NT woodland covering over 400 acres (160 hectares) of unspoiled valley featuring tumbling streams, waterfalls, and steep ravines, with more than 15 miles of footpaths for exploration and the historic, off-grid Gibson Mill. Close to one of the worst-hit 2015 flood sites near Hebden Bridge, West Yorkshire, it was the ideal location for trialling some of the simple solutions Slow The Flow had developed.
Under the watchful eye of NT rangers, Slow The Flow recruited volunteers to build leaky woody dams throughout Hardcastle Crags. Over the next eight years, this unique partnership and hundreds of volunteers built over 1,000 leaky woody dams, miles of contour logs, and storage for rainwater near the river at strategic locations, all with the aim of slowing the flow of rainwater into the river network in the valley bottom.
At Crimsworth Dene, a valley running towards Walshaw Moor and part of Hardcastle Crags, monitoring equipment and time lapse cameras were installed to study how the leaky dams were slowing the flow and measuring their efficacy. Monitoring and citizen science have always been important parts of Slow The Flow’s work – one of the reasons that nature-based solutions (NBS) don’t receive the funding they deserve is that their benefits are harder to quantify; the more their worth can be proven, the easier those holding the purse strings find it to invest.
This pioneering work at Hardcastle Crags continues, with the NT now managing the work completed over the past eight years. A smaller project is also under way at Broadhead Clough, a Yorkshire Wildlife Trust (YWT) site in Cragg Vale, to install a smaller number of leaky woody dams.
You can read more about these projects, and all of our other work that there isn’t space for in this article, at www.slowtheflow.net.
Building a communication strategy
Slow The Flow and its volunteers became regular contributors to local and national media as other communities became aware of the work being carried out at Hardcastle Crags. Robust and strategic communication played a huge part in ensuring that communities from around the UK and further afield could learn from Slow The Flow’s knowledge and experience of these pioneering, nature-based solutions.
Connecting with a broad audience was, and remains, key in advocating for nature-based solutions (NBS) to become the go-to solution to flooding. Hard engineering also has its place; working with nature, however, is not only often less financially costly, but offers benefits to water and air quality, biodiversity, and public amenity. Unlike hard-engineered schemes that address flooding at a single point, nature-based solutions can work across whole catchments, delivering multiple benefits simultaneously. The Slow The Flow website, newsletter and social media channels provide a wealth of information, ranging from the easily accessible to contributions from top scientists working in the field.
In 2020, Slow The Flow was awarded charitable status as an educational charity; and in 2021, as the UK came out of Covid-19 lockdown, the Lord Lieutenant of West Yorkshire awarded Slow The Flow the Queen’s Award for Voluntary Service. This accolade is ‘the MBE for volunteer groups’, recognising Slow The Flow and its volunteers’ crucial work to reduce flood risk in our towns and villages
You too can Slow The Flow
Using its practical work as example, Slow The Flow has led the way in promoting the merits of NFM and Sustainable Drainage Solutions (SuDs) schemes, both in Calderdale and nationally. As a result, nature-based groups, public bodies like Calderdale Council and The Environment Agency, private companies like Yorkshire Water, individual landowners and households have begun to invest in nature-inspired schemes to reduce the risk of flooding.
NFM has now broadly been accepted, but there is still a lot of work to do to make NFM and SuDS more mainstream and fundamental to policymakers and legislators around the UK.
The imperative is to promote NFM and SuDS to an ever wider audience and encourage their installation as ubiquitously as possible.
Slow The Flow acknowledges that NFM and SuDS alone will not prevent flood risk. Communities will still also need hard-engineered schemes to protect them, particularly when flooding is only likely to get worse and more frequent due to climate change, but NFM and SuDS can make significant contributions (see our ‘opportunity mapping’ and report) while offering cost-effective methods of reducing flood risk which can sit very sympathetically alongside traditional flood alleviation schemes.
Slow The Flow has published many articles on how individuals and communities can make small incremental changes to their homes, businesses, public buildings and schools. Leaky dams, tree planting, attenuation ponds, de-paving, rain garden planters and water butts at our homes, and thinking about using natural solutions in all developments all contribute to reducing flood risk. Slow The Flow believes that we all have a responsibility in our communities to ensure such simple and low-cost solutions are developed, innovated and exploited.
The simple call to action, You Can Slow The Flow is one everyone can participate in to play a small part in reducing flood risk.
Our Five Key Messages
Slow The Flow has now visited the Houses of Parliament twice, and also made a short film to promote its Five Key Messages:
1. Rebalancing of the funding formula to support nature-based solutions.
2. Education on Natural Flood Management (NFM) in schools.
3. Promotion of Green Economy jobs and infrastructure.
4. Implementation of Schedule 3 of the Flood & Water Management Act (FWMA) for SuDS.
5. Resolve sewage overflows and improve water infrastructure.
These Five Key Messages have become instrumental in the Slow The Flow communications strategy to educate legislators and decision makers, and to ensure they are pro-active in their policy making around NFM, SuDS and water management.
Slow The Flow continues to court the attention of legislators and decision makers. After Slow The Flow’s first visit to Parliament, Emma Hardy MP, now parliamentary under-secretary of state for water and flooding, came to talk with trustees and subsequently visited the work of Slow The Flow sister project, West Wolds Slow The Flow. The government’s recent announcement of a re-balance of flood resilience funding towards nature-based solutions is an indication of the influence that communities can have.
In the Spring of 2025, Slow The Flow briefed several members of parliament at Hardcastle Crags on its work and on the Five Key Messages. The MPs included the two Calderdale MPs; Josh Fenton-Glynn, MP for The Calder Valley, and Kate Dearden, MP for Halifax, as well as Toby Perkins, MP for Chesterfield and chair of the Environment Select Committee.
The importance of peat
Slow The Flow has also written extensively on upland management and the importance of peat. At present, this information is proving useful in promoting understanding of the flood risk implications of wind farm development on deep peat moorland. It is clear that for best NFM practice, deep peat should not be disturbed. Josh Fenton-Glynn MP has taken this message to parliament to argue that peat bogs should be protected and Slow The Flow is delighted that this message has been conveyed through the channels at Westminster.
What about the next 10 years?
Slow The Flow’s focus is now firmly on providing education on and exploring and developing the merits of working with nature to reduce flood risk. Slow The Flow has developed modules aligned with the National Curriculum in Geography at KS2 and KS3 to provide in-school education on the issue of flooding and the solutions around NFM.
Slow The Flow has already taught this module at around 20 schools in Calderdale and has ambitions and plans to increase this capacity to other locations, ultimately throughout the United Kingdom. If you are an educator and would like to help Slow The Flow realise this ambition, contact secretary@slowtheflow.net.
In 2026, Slow The Flow is also looking to appoint its first paid Project Manager to build upon the success of the last 10 years by working with schools and communities to promote and utilise NFM here in the Calder Valley and further afield. Having a full-time member of staff will mean that the work undertaken in the last 10 years can be developed and escalated. If you are in a position to assist with funding this next step, please get in touch at secretary@slowtheflow.net.
Work with central and local government continues and, as the climate crisis intensifies, it is imperative that communities find solutions to reduce and manage the growing threat of flood risk. There are numerous other groups like Slow The Flow in the UK, like Harborough Woodland in the north Midlands, West Wolds Slow The Flow in East Yorkshire, and Flooded People UK who work with flooded communities. The National Flood Forum and the wonderful ‘Flood Mary’ Dhonau all make huge contributions to this work, and professional bodies like the Construction Industry Research and Iinformation Association (CIRIA), Institution of Civil Engineers (ICE) and the Landscape Institute are helping to raise awareness amongst their members. These combined efforts will continue to pressure and lobby the government to do more on this issue.
The voluntary sector makes a huge contribution to so many areas in our society and our communities. Groups like Slow The Flow need to continue to influence and lobby to rebalance the flooding funding formula, to ensure that water companies improve the water infrastructure including the implementation of Schedule 3 of the Flood & Water Management Act, ensuring there is no automatic right of developers to connect to the sewage system and to provide a sustainable drainage solution in every build, as well as having a Natural Flood Management strategy in every local authority and to promote the green economy.
Born out of the basic desire to make a difference and reduce flood risk on a local level here in the Calder Valley, Slow The Flow’s influence has now permeated throughout the UK and beyond.
Slow The Flow is hugely proud of all that has been achieved in the last 10 years and looks forward to what might be achieved in the future. Dedicated people, working on a local level, innovating and collaborating to find simple solutions, and educating both the public and decision makers, including working to influence policy locally and nationally, is what has made Slow The Flow a success.
