Internal Drainage Boards (IDBs) are independent ‘operating authorities’, created under statute to manage land drainage in areas of special drainage need and are mainly to be found in the lowland areas of East Anglia, Somerset, Gloucestershire, Yorkshire and Lincolnshire.

Each Board operates within a defined area, known as a Drainage District, in which it is empowered under the Land Drainage Act 1991 to undertake flood defence works, on any watercourse except those that have been designated as ‘main river’, and consequently come under the control of the Environment Agency.

Internal Drainage Board membership includes elected members representing the occupiers of the land within the Drainage District and members nominated by the local authority to represent the interests of the general public and other interest groups.

IDBs are funded by a Drainage Rate charged on the occupiers of agricultural land and by a ‘Special Levy’, charged on the local authority.

Where an IDB undertakes capital flood defence works, Grant Aid is normally available from DEFRA to meet a proportion of the cost. Usually this is at a rate of 45%, but special rates are available for works to implement water level management plans (WLMPs) on certain sites of conservation interest. The special rates, which may be as high as 80% for sites of international conservation importance, are made in the recognition that IDBs are partly funded by private landowners, while the works in question are intended to provide benefits nationally.

West Mendip Internal Drainage Board

The West Mendip Internal Drainage Board has an operational area (Drainage District) covering some 5,859 hectares (14,477 acres) of low-lying land extending from the coast at Uphill, inland through Hutton and Banwell, to Sandford, Churchill and Congresbury, then along the Congresbury Yeo to the coast at Wick St Lawrence. The boundary then continues around the coast, skirting inland of Sand Point to Sand Bay and Kewstoke, then through Worle, Milton and the central part of Weston-super-Mare, back to Uphill.

The boundary of this area is broadly defined by the 8.0metre (25foot) contour line and all the land within the Drainage District is below sea level at the Mean High Water Spring Tides.

Within this area the Board has a duty to exercise a general supervision over all matters relating to the drainage of land.

The Board directly controls and maintains 92.1km (57.25miles) of Viewed Rhynes [will increase to 97.1km (60.3miles) when West Wick and St Georges Areas included] and 37 water control structures. In addition, the Board has direct responsibility for two major sea outfalls, one at Sampson’s Sluice on the Oldbridge River and the other at Hucker’s Bow on the Kewstoke Rhyne system.

Whilst the Board has powers to undertake works on any non-main river watercourse within its District, direct maintenance is limited to the Viewed Rhynes, which form the strategic arterial drainage system. All other minor watercourses and field ditches are the responsibility of the adjoining, riparian, landowner to maintain.

The Board also manages water levels in the arterial drainage system, particularly during summer months, to maintain an adequate water supply for agricultural purposes and wet grassland conservation.