Beavers’ dams cause localised flooding, creating wetland areas which benefit biodiversity, but they actually help to reduce the risk of flooding lower down in river systems, since the dams moderate water flow.
This system is effective in dealing with normal levels of rainfall.
The cause of the Alyth flood was exceptionally heavy, prolonged rainfall which significantly increased the volume of water in the burn.
The torrent of water carried everything with it – trees, large branches, and, no doubt, beavers’ lodges.
The obvious conclusion to be drawn from the presence of lodge material is not that the lodges caused the flood, but that they, and the beavers, were also victims of the flood.