Slow the Flow and Natural Flood Management

Llangattock Community Council have been exploring the possibility of a Slow the Flow scheme on the Onneu Fach initially, but also could be considered for other local streams that feed into the Usk River. We have been working alongside Powys County Council and the Wye & Usk Foundation.


What is Slow the Flow?

Natural flood management aims to reduce the downstream maximum water height of a flood (the flood peak) or to delay the arrival of the flood peak downstream, increasing the time available to prepare for floods. The myriad Slow the Flow items work together, helping to reduce flow rate in the valley, under storm events. This is achieved by restricting the progress of water through a catchment in 3 ways:

  • Increasing soil infiltrationand allowing water to soak away.
  • Storing water by using natural features such as ponds, ditches or low lying land or by creating new ponds and areas to store water.
  • Slowing water by increasing resistance to flow. For example, by planting trees on the floodplain or constructing “leaky dams” in channels.


What is a “leaky dam”?

Leaky dams form naturally when large sections of trees fall into and across the channel. These large pieces of wood start to gather smaller sticks and leaves which allows some water through, but holds back some of the water in the stream during high flows.

We can mimic nature by building leaky dams using locally sourced wood. The leaky dams can be pinned in place or dug into the bank to ensure they don't move around in high flows. Building a series of dams along a section of stream increases the effectiveness of the dams.

Woody debris helps to create pools and riffles, providing a variety of habitats for fish and aquatic insects and attracts mammals and birds. Importantly leaky dams can slow the movement of silt and sediment downstream. Silt can increase flood risk by reducing the amount of space for water in a channel.




A new type of river management:

Useful websites: 

Calderdale Slow the Flow Charity

Slow the Flow in the Calder Valley video on YouTube

Pickering Slow the Flow scheme

Susdrain: The community for sustainable drainage, more info and ideas:

Yorkshire Water: tips on water saving:

Lowland Natural Flood Management Measures – a practical guide for farmers A detailed guide to different levels of NFM interventions, their costs and benefits:

Yorkshire Dales: Natural Flood Management Measures – a practical guide for farmers Similar to the above but with examples of Upland NFM:

West and North Northamptonshire Councils: Flood Toolkit - An impressive resource of information by a pioneering Lead Local Flood Authority (LLFA), including the ‘Flood Library’ of guidance documents.



What residents can do to help

A friendly, vibrant, forward-thinking village in the South East corner of the county of Powys. We are surrounded by the stunning scenery of the Brecon Beacons National Park. 
Keep up to date
Please enter your email to receive newsletters and updates from Llangattock Community Council. This also gives us permission to use your contact details to keep in touch. For more information about how we will use this your information, see our terms and conditions at the bottom of this page.

Please select the ways you are happy to hear from Llangattock Community Council:

Click for more information

You can unsubscribe at any time by clicking the link in the footer of our emails. For information about our privacy practices, please visit our website.

We use Mailchimp as our marketing platform. By clicking below to subscribe, you acknowledge that your information will be transferred to Mailchimp for processing. Learn more about Mailchimp's privacy practices here.
Follow us on Facebook