A watercourse is any natural or artificial channel above or below ground through which water flows, such as a river, brook, beck, ditch, mill stream or culvert.

If a watercourse runs through or next to your land you are a 'riparian landowner' and you will have responsibility for managing the watercourse.

Formerly known as 'main rivers', watercourses are designated by the Department of Infrastructure and are of general significance for flood risk management (FRM).

We may provide, maintain, improve or extend designated watercourses or FRM works to protect the Island from flood risks.

We may provide, maintain, improve or extend non-designated watercourses or FRM works only if:

  • there are circumstances posing a serious flood risk
  • to mitigate the consequences of flooding





Works Affecting Watercourses

It is a criminal offence to carry out works which affect flood defences or watercourses without permission from us. If you wish to carry out works affecting watercourses in the Isle of Man please complete an application for consent for works affecting watercourses. 

Explanatory notes are available for further guidance.  Riparian owners can find further information on watercourse management here.