The law in relation to land drainage is generally to be found in the Land Drainage Act 1991. This area of law includes such matters as:
- duties on landowners to drain land and protect land from flooding and the powers of drainage authorities (variously, IDBs, NRW and the Welsh Ministers) to do so;
- powers to undertake drainage works;
- controls of obstructions and structures;
- powers to make drainage byelaws;
- environmental duties of drainage authorities, and Ministerial powers of direction of an IDB;
- improvement works, subject to restrictions including those relating to environmental impact assessments.
Internal Drainage Boards are independent statutory bodies responsible for land drainage in areas of special drainage need in England and Wales, sometimes referred to as internal drainage districts (IDDs).
They are long established public bodies operating predominantly under the Land Drainage Act 1991 and have powers to undertake work to secure drainage and water level management within their districts, including undertaking flood defence works on ordinary watercourses.
IDBs also hold a number of duties and functions under other items of legislation, and many have their roots in private Acts; Acts of Parliament that relate to a specific area.
Since 1 April 2015 NRW exercises the land drainage functions in respect of the IDDs in Wales. The IDBs operating in Wales were abolished with functions transferred to NRW.