Willow: an environmentally friendly way to protect our riverbanks from erosion
Bank erosion is a natural process. However, river users, dog and livestock entry points, lack of vegetation and flooding all accelerate this process. This causes sediment to enter the river which pollutes habitat and smothers species such as freshwater pearl mussels.
Green engineering is an environmentally friendly way to tackle this, it uses natural materials to re-enforce the riverbank. Willow spiling is just one example. Living willow posts are knocked into the riverbed and living willow is then woven around each post creating a strong living wall to stop erosion and catch sediment before entering the river. Brash bundles and large timber logs are then placed behind the wall to backfill the structure and promote faster recovery.
It’s great for the environment as the living structure increases biodiversity; female willow plants provide a food source for butterflies and bees whilst the structure itself creates habitat for birds and shade for aquatic species such as Atlantic salmon and freshwater pearl mussels.
The flexibility in the willow weave dissipates the power of water during high flows therefore reducing the impact of flooding and reduces damage to the structure. Encouraging the growth of vegetation behind it slows and disturbs any water flow to further reduce the impact of flooding.
Like anything that is living, willow needs long term management and is cut on a two-year cycle to ensure growth is focussed on the root system and the weight is minimised but its benefits in bank stabilisation, sediment reduction and re-vegetation have established it as a fantastic material in the challenge of against bank erosion.