Purpose of an Internal Drainage Board

IDBs cover 1.2 million hectares of England (9.7% of England’s total land area) and 28,500 hectares of Wales (1.4% of Wales’ total land area), 90% of the indicative flood map zone 3 for England and Wales.
24 of the county councils in England include one or more IDB in their area as do six metropolitan districts, and 109 unitary authorities or district councils.

IDBs are geographically concentrated in the Broads, Fens in East Anglia and Lincolnshire, Somerset Levels, Kent, Nottinghamshire and Yorkshire covering growth areas such as the Thames Gateway and Milton Keynes & South Midlands, and existing developed areas of the Thames gateway, East Midlands and the Humber Estuary.

Their 570 staff operate and maintain over 500 pumping stations, 22,000 km of watercourse, 174 automatic weed screen cleaners and have a part in providing flood risk management to 879,000 properties. They also have responsibilities associated with 398 Sites of Special Scientific Interest plus other designated environmental areas.

IDB Districts include the majority of England and Wales’ highest grade agricultural land, urban areas providing 879,000 homes, industries of national importance and much of UK’s critical infrastructure, including; 20 oil refineries and power stations, 68 other major industrial premises and 208 km of motorway. This essential and critical IDB activity must continue alongside and complimentary to any new role.


To realise this Vision we need IDBs to:
  • be recognised as competent FCERM authorities
  • play a full part in local partnerships
  • have a distinct role working with other relevant authorities
  • become ‘delivery partner’ of choice for Local Lead Flood Authorities and other partners
  • build capacity and adjust to deal with new challenges
  • adapt in the face of climate change.


  • carefully manage water levels within their drainage districts for;
    • land drainage,
    • flood risk management,
    • irrigation,and environmental benefit.
  • work within hydrologically defined catchments.
  • operate in areas of special flood risk.
  • be recognised as the land drainage authority within their Districts.


  • through the functions listed above, sustain land use, including inhabitation, agriculture,industry, recreation and natural habitats.
  • play their part in delivering UK food security:
    • by providing and regulating irrigation and drainage for hundreds of thousands of hectares of agricultural land (including land of the highest quality) in England & Wales.
  • contribute to the security of civil infrastructure within their Districts.
  • aid the sustainability of rural and urban communities.
  • help maintain Defra’s commitment to the ABI over flood risk management to properties, and the consequent availability of flood insurance.


  • liaise with all relevant stakeholders, FRM delivery partners and Government.
  • conduct their activities with regard to Local and National Government strategies.
  • actively shape and comment on local and regional policy decisions.
  • play an active role in development planning decisions within and surrounding their Districts.


  • be representative of the communities they serve through elected and appointed Board membership.
  • raise funds locally for water level management.
    • IDB Special Levy
    • Agricultural Drainage Rates
  • balance the priorities and stakeholder views within their Districts.


  • promote the ecological wellbeing of their Districts.
  • work to help maintain and improve all SSSIs and other designated environmental areas within their Districts
  • develop and implement IDB Biodiversity Action Plans
  • work towards reducing and mitigating their climate change impact.

The full ADA vision can be found here - A Vision for Internal Drainage Boards in England and Wales

NB: The above information is published under the kind permission of the Association of Drainage Authorities.

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