About IDBs

An introduction to Internal Drainage Boards

An Internal Drainage Board (IDB) is an independent local public authority that manages water levels in England where there is a special need for drainage. IDBs undertake works to reduce flood risk to people, property and infrastructure, and manage water levels for agricultural and environmental needs.

Each IDB has permissive powers to manage water levels within their drainage district, carefully maintaining rivers, drainage channels, culverts, sluices, weirs, embankments and pumping stations.

They also play an important regulatory role, using powers to keep water courses clear of obstructions. They set byelaws to ensure the watercourse network works efficiently, and they scrutinise planning and development in their area to mitigate its impact on the water environment and flood risk.

Where can I find an IDB?

IDBs manage water levels in drainage districts; areas where there is a special need for drainage. They either occur in broad open areas of lowland such as the Fens, Somerset Levels or Humberhead Levels or within the floodplains of rivers. The drainage district each IDB covers is determined by the local hydrology and not by political boundaries such as those of counties.

There are currently 112 IDBs in England covering 1.2 million hectares (9.7% of England’s land area). Wales also has 28,500 hectares of drainage districts that are managed by Natural Resources Wales through local Advisory Groups.

How are IDBs funded?

IDBs annually invest over £60 million in managing water levels and reducing flood risk. The cost of undertaking their essential functions are predominantly funded by the local beneficiaries of the water level management work they provide.

Each IDB sets a budget for its planned work in the forthcoming year and any investments it needs to make for future projects. Section 36 of the Land Drainage Act 1991 determines that these expenses of an IDB shall be met by:

Drainage rates collected from agricultural land and buildings within the Internal Drainage District;

Special Levies issued on District and Unitary Authorities within the Internal Drainage District;

Contributions from the Environment Agency (see Higher Land Water Contributions).

Who governs an IDB?

An IDB is governed by its Board that consists of members, who are either elected for periods of three years from the agricultural drainage rate payers (‘elected members’); or appointed for periods of up to three years by levy-paying local authorities (‘appointed members’).

The number of appointed members relates to the proportion of an IDB’s total income derived from special levy but appointed members may not exceed by more than one the number of elected members. In this way IDBs retain strong local accountability to those within their drainage district that they serve.