This guidance sets out the basis on which the Environment Agency should decide whether or not a river or watercourse is treated as a ‘main river’.
Main rivers are usually larger rivers and streams, designated as such, and shown on the Main River Map. The Environment Agency carries out maintenance, improvement or construction work on main rivers to manage flood risk. Other rivers are called ‘ordinary watercourses’. Lead local flood authorities, district councils and internal drainage boards carry out flood risk management work on ordinary watercourses.