This includes any structure or appliance for controlling or regulating the flow of water in, into or out of a main river.
Main rivers are usually larger streams and rivers but also include some smaller watercourses. In Wales, main rivers are legally designated by Natural Resources Wales.
If you want to carry out works in, over, under or near a main river, or in a flood plain or flood defence (including a sea defence), you will need to apply for Flood Defence Consent.
Natural Resources Wales’ powers to carry out flood defence works apply to main rivers only.
Every other open watercourse in Wales is known as an 'ordinary watercourse' and falls under the responsibility of your local authority (as the Lead local flood authority).