What is "Slow the Flow" all about?
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. This is achieved by restricting the progress of water through a catchment in 3 ways:
- Increasing soil infiltration and 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.
What's happening in Shropshire?
We are currently working with our partners and private land owners in several priority catchments to map the different habitats, land uses and drainage issues. We will be looking for opportunities where we can work with nature to help slow the flow.
If you would like to know more about the Shropshire Slow the Flow project please contact Luke Neal via email at LukeN@ShropshireWildlifeTrust.org.uk
What's going on elsewhere?
See what our friends in Gloucestershire have been doing to tackle flooding in the Stroud Valleys.
The link below will take you to a shorter 3min taster version:
Stroud District Council have also just released this fantastic video that gives a great explanation of the more technical details of natural flood management. Watch it at this link:
Thanks to the Stroud Rural Sustainable Drainage Project for making these videos available.