Willow Spiling: Review of Streambank Stabilisation Projects in the UK

At least 47 km of riverbank in the UK has been protected by willow spiling during the last 20 years and willow spiling is now the most widely used willow-based method for erosion control in the UK. Long willow canes are woven around vertically driven willow poles and because structures are living, resistance to erosion increases over time. Willow spiling has, alongside its geotechnical stabilisation function, numerous ecological and economical benefits for river restoration, habitat enhancement and community engagement. In this review, we select eight critical factors to consider when applying the method, based upon previous research and practical experience, and we explore knowledge gained from nearly 140 UK willow spiling projects. Information on performance has been collected from 27 % of the projects. Of these, 59 % were very successful, 30 % involved partial failure and 11 % failed completely. Although extreme flooding or drought can cause failure, most of the failures could have been limited by a better understanding of the site conditions in relation to willow requirements, by correct installation, by using good quality willow and by carrying out prompt repairs. Reasons for failure are documented and discussed. The importance of monitoring and maintaining the site after construction is emphasised.