Using Willow For Environmental Protection
- Flood Control
- Bio Engineering
- Bio Filtration
Willow for Environmental Protection
Willow is naturally tough, strong and versatile and can be used in a wide range of circumstances to protect the environment and communities from both short term extreme events and longer term environmental problems.
A major contributing factor to the frequency and severity of recent flooding is land management in the upper reaches of water catchment areas. Lack of shrub and tree cover and extensive drainage over large areas of land encourages rainwater to run off the land quickly thereby causing floods in rural villages and urban areas downstream. Often referred to as surface roughness tree and shrub cover slows down the flow of water over the surface whilst the roots provide channels for water to penetrate into the soil more effectively. Willow Short Rotation Coppice, SRC, planted on the bottom of slopes and at field edges is a quick and effective method of increasing surface roughness. Willow coppice with its multiple stems is also effective at trapping any soil and debris being carried in any run off and can also be used to dam the drainage channels that were used to increase the speed of drainage off these areas. At the same time the willow coppice will also provide a carbon neutral source of wood fuel and/or serve as a windbreak for people, livestock and crops.
Bio engineering simply means using biological components in an engineering solution to a particular environmental problem. There are a wide variety of examples in use today including the following:
This is the use of living willow hurdles as reinforcement for an existing or modified river bank and as the retaining wall on a terrace system designed to prevent soil slippage on steep or vulnerable banks. The hurdles are usually made on site by weaving flexible live willow rods around thicker live willow posts driven into the ground at intervals. Soil is back filled behind the live willow hurdle enabling the woven live willow rods to root into the soil further stabilising the bank.
Brush matting is used to protect river banks that are vulnerable to scouring when a river is in spate. Live willow rods are laid on the bank with their butts dug into a trench. The live willow rods are anchored to the bank with rods and pegs. This has the effect of creating a barrier of willow protecting the river bank. Protection of the bank is further enhanced when the willow rods take root binding the soil with their fibrous root system. New growth above ground will also protect the bank by absorbing the energy of fast moving water.
Bundles of live willow known as faggots or fascines are placed in trenches dug across a slope. These prevent any further erosion down the slope and as the willow grows it traps any eroding soil to further stabilise the slope. This is a popular method in mountainous areas of Europe subject to the erosion of steep slopes by water.
As the name suggests this is filtering a range of bio degradable waste matter using plants. Willows have many qualities, most notably super fast growth and sheer toughness and versatility which make them suitable for a wide range of filtration purposes. The most simple and direct example is to use farm slurry or treated sewage as a fertiliser on a willow biomass plantation. Being super fast growing willow can absorb large amounts of waste and nutrients that would otherwise be toxic in such large amounts and convert it into useful biomass that can then be converted into heat and/or energy. Buffer zones of willow are often planted to intercept fertiliser run off from modern intensive farms thereby protecting rivers and watercourses from excess nitrification which undermines natural river ecology. When river levels are low in summer willow plantations planted on land fill sites are used to re cycle toxic run off, again preventing toxins from entering the surrounding watercourses.