Using flood-excess volume to show that upscaling beaver dams for protection against extreme floods proves unrealistic

The questions we address in the present aricle are the following: (i) whether (extreme)river floods can be prevented or seriously mitigated by the introduction of beavers inthe wild, and (ii) for which river catchments does flood mitigation by beaver activity(not) work? By using the concept of flood-excess volume (FEV) for four rivers in theUK, in the context of five (extreme) UK flood events in the last two decades, we showthat even a 10% flood reduction of the FEV, using beaver colonies and beaver dams,requires hundreds of such colonies per river catchment. Given the high number of beavercolonies and dams required for mitigation, we conclude/demonstrate that serious floodmitigation by massive introduction of beaver colonies is completely unrealistic, in starkcontrast to statements made in scientific literature and in the media. Furthermore, FEVis valuable beyond its utility as a tool in analysing the efficacy of beaver dams as floodprotection: it is demonstrated to be a useful tool for assessing in an easy-to-understandway a variety of flood-mitigation measures, including analysing the scalability of localflood-mitigation measures for overall catchment needs.