Are ‘free-flowing rivers’ a good idea? The challenge of removing barriers from our rivers

The removal of barriers from rivers is a controversial topic. Barriers come in many forms including weirs, dams, sluices and bridges. Mills are listed in the 11th-century Domesday Book and shown on early Ordnance Survey (OS) maps, often with their use marked ‘corn’, etc. So, what are the arguments for removing them? As this article shows, these relate to the creation of more natural flow regimes and the re-establishment of a connection between the river channel and the floodplain. The most obvious practical benefit is that migratory fish will find their upstream passage easier. The disbenefits are provision of access for invasive species and the loss of flood control structures. On the River Rother in West Sussex, UK, the release of sediments stored behind weirs is a potential ecological hazard. In Britain, few barriers have been removed and instead fish ladders have been installed. In the USA and Europe, dam removal is well advanced. The European Commission (EC, 2020) aims to achieve 25,000km of ‘free-flowing rivers’ by 2030 with a focus on removing ‘obsolete barriers’.