An ordinary watercourse is one of the two types of watercourse in statutory language in England and Wales. Ordinary watercourses include every river, stream, ditch, drain, cut, dyke, sluice, sewer (other than a public sewer) and passage through which water flows and which does not form part of a main river. An internal drainage board where relevant, or lead local authority has permissive powers to carry out flood defence works for ordinary watercourses at their discretion.