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.