Main rivers

Our flood risk map shows the watercourses defined as main rivers in Wales.

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 a Flood Risk Activity Permit.

Find out how to apply for a flood risk activity permit for work on a main river 

Natural Resources Wales carries out maintenance, improvement or construction work on main rivers in Wales to manage flood risk.

Every other open watercourse in Wales is known as an 'ordinary watercourse'. Your local authority (as the lead local flood authority) or Natural Resources Wales (as the internal drainage board) carries out maintenance, improvement or construction work on ordinary watercourses in Wales to manage land drainage. 

If you own land or property next to any river, you will have responsibilities as a riverside property owner.

Find out more

If you would like to understand more about main river designations, or discuss potential changes to the main river map, please contact us.