A recent video providing an overview of why we need to slow the flow, how we are doing it and our volunteers in action!
We are very proud to announce that we have won two awards
We are a 2017 winner of the the Sustainable Water Industry Group Awards for our Sustainable Drainage System project. Huge congratulations is due to our own Amanda McDermott, who has developed this work.
Community Foundation Great & Green Award 2017 WINNERS
Case Study 1: Flood alleviation at Oldroyd, Todmorden, Upper Calder Valley
On Boxing Day 2015 the hamlet of Oldroyd (OS 3949 4241) which comprises a street of former mill or farm workers cottages dating from the 19th century, was partly inundated by flood water running off adjacent sloping fields, a total of five properties were affected, similar problems occurred during the summer floods of 2012.
The residents were keen to install large diameter pipes across fields to collect the excess water and discharge it downstream away from their properties as quickly as possible. However, such a scheme would prove to be outside of the budget of £25,000 for the works as the cost of the pipes alone exceeded this figure.
The project was funded by the Repair and Renew Grant Scheme run by Calderdale MBC following the Boxing Day floods, this was a central government grant made available to homeowners and businesses whose properties were flooded or very narrowly avoided being flooded. A much more cost effective scheme was put forward by Slow the Flow Calderdale civil and structural engineer Stuart Bradshaw which required the excavation of an attenuation pond to temporarily store water, and then slowly release it once the storm had passed.
This would solve the flooding issue for the residents of Oldroyd yet at the same time it would slow the flow of water to the River Calder with consequential benefits for the downstream communities of Hebden Bridge, Mytholmroyd, Luddenden Foot, Sowerby Bridge and Elland all badly affected by flooding on Boxing Day 2015. Neighbouring farmers who owned the land that would be used for the works were assured that their fields would be returned to pasture once the works were completed.
The scheme comprises an interception channel which is simply a trapezoidal cross sectional channel dug across the bottom of the hillside above the properties, this diverts the water away from the properties to flow into an attenuation pond with an approximate volume of 800 m3.
The attenuation pond has a 150 mm diameter outlet pipe which allows water to flow out of the pond at a rate of around 25 l/s leaving excess water to rise and be stored temporarily in the pond. The maximum depth of the water is less than 1.0 metre and due to the fall in the land most of this water is stored below the former existing ground levels by digging into the hillside and using this soil to create a low embankment on the lower side. The attenuation pond should provide protection for up to a 1 in 50 year storm, storms of a greater intensity will over top the pond but water then flows over a weir on the dam crest which directs the water away from properties and onwards downhill on a flow path that takes it away safely.
After nearly a year working with The National Trust at Hardcastle Crags, we have now built 117 leaky woody dams using over 100 volunteers. Our volunteers have worked incredibly hard in 2017 and we simply would not have achieved what we have without all this incredible help. A massive Thank you if you have helped in any way on this project.
Early indications are that these leaky woody dams in Hardcastle Crags are working to slow the flow and reducing the impact of flood water finding its way down the Calder Valley. Formal results of how much water has been slowed will be published in the New Year!
Certain in the knowledge that what we are doing works to reduce the impact of amount of water finding its way to our towns and villages, we will continue into 2018. However, we still need volunteers to continue with this important work. If you can help in any way whatsoever, please do get in touch or come to one of our volunteer days at Hardcastle Crags.
There is still lots to do, not just in Hardcastle Crags, but across the Calder Valley and we are working with our partners to identify other areas which would benefit from the installation of these leaky dams. If you know of such an area, please do get in touch so we can arrange a survey and see how we can Slow The Flow near you.
After over a year in the planning, and with the recent grant made from The Calder Flood Partnership to The National Trust for work at Hardcastle Crags to ‘Slow The Flow’, volunteers have started work in the gullies leading into the river which flows into the River Calder.
New equipment has been bought, natural materials have been sourced and managed and volunteers have been recruited and trained to build leaky dams and for gully stuffing throughout the Crags.
To date, around 100 new volunteers have worked in this beautiful part of the Calder Valley and significant progress has been made in a number of gullies leading into the main channel in the Crags.
Volunteers ranging in age from 10 to over 70 have taken part. Work ranges from sawing timber, trimming brush, digging, and moving trunks into place to form leaky dams and to stuff gullies to encourage rain water onto the banks during heavy rainfall. The channels still work in normal flow but to try and reduce the amount of water making it into the main channels, the gully stuffing and leaky dams force the rain water over the banks and onto the slops.
This programme will continue throughout the summer in the Crags so if you want to get involved, contact us here to book your place. We usually start at 9.30 am and finish by lunchtime, currently over weekends.
Work parties are also being arranged during the week so if your company or organisation would like to get involved, please contact is here register with us. We already have 3 large organisations who will be working with us throughout the summer.
You will need to fairly fit although you will not be expected to carry heavy weights or work beyond your own limitations. All we ask is that you have a desire to help ‘Slow The Flow’. There are a range of tasks suitable for all ages as we have already demonstrated with our amazing volunteers who have helped to date.
IMPORTANT INFORMATION ON CHILDREN WHO WANT TO VOLUNTEER – children under 18 are VERY welcome to volunteer but they must be supervised by you at all times. Please be aware that there are chain saws in use (solely by fully trained personnel) and dangers associated with: mechanical and manual movement of very heavy logs; unsupervised saws and other blades laid on the ground; and axes and saws in full swing. It is possible to work in areas where some of these dangers are not present but they may be adjacent to areas where they are present.
Timelapse of Hardcastle Crags on 20th-22nd November showing impact of Storm Brian and Natural Floor Management interventions.
The environment agency published a series of evidence based reports on working with natural processes to reduce flood risk.
Look here for details of the reports