Spiling is a traditional technique used for the prevention of erosion to river and stream banks, and is a very successful method of riverbank stabilisation. Willow spiling is where live willow rods are woven between live willow upright stakes which have been driven into the river bank. The area behind can be filled with soil for the willow to root into. During Spring and Summer, these living willow rods and posts send out shoots and root into the river bank, hence holding the soil firm and resolving the erosion issues.
The species of willow used are riparian, and the posts, say 5 to 10cm (2 to 4 inches) in diameter, are usually Salix alba or Salix fragilis, and Salix viminalis varieties are used for the interwoven rods. The living willow posts are driven into the bank, to a depth of approximately 30 centimetres (1ft) or more, at 60cm (2ft) intervals, and the thinner rods are woven in between.
The rods are best woven at an angle slightly above horizontal to ensure good survival rates. A row of stones, gabions or wooden planks held by posts can be added to the bottom of each spile to prevent undercutting when the willow is establishing itself if necessary. A layer of willow matting can be pegged onto the soil on top of the spiles to prevent the soil being washed out during flood events.
This method is an example of soft engineering techniques which tend to be less expensive and more sustainable than many others, helping you to work with nature, rather than against it, and requires minimal heavy equipment therefore causing least disturbance to river & stream environments. Mud and silt is gradually deposited in and around the rough surface of the willow spiling, with the spreading willow roots stabilising the river bank and creating a natural wildlife habitat.
Erosion control using willow spiling is particularly suitable on sites with reduced access, as materials can be carried onto the site and in many cases the entire project can be constructed by hand.
At Coates Environmental we grow, process and supply a wide range of willow products and materials that are ideal for waterway spiling and natural river bank stabilisation projects. We can supply willow rods, willow stakes and willow spiling for you to install your own erosion control or if you simply wish to enhance the aesthetics of your streams and river banks.
Please contact us to find out about current stocks and advice for you spiling requirements.