Conservation Policy


The Black Sluice Internal Drainage Board has adopted this Policy, which sets out how it intends meeting the duty placed on Internal Drainage Boards under the provisions of the Land Drainage Act 1994 and other relevant legislation, to undertake watercourse maintenance and water level management in a way that is compatible with Nature conservation interests.

The Board recognises the need to positively demonstrate that its watercourse maintenance and water level management are carried out in a manner that reduces flood risk, safeguards nature conservation interests and wherever possible makes a positive contribution to the enhancement of the natural environment.

Defra required all IDB’s to have a Biodiversity Action Plan (BAP) written by April 2010. 

Download a copy of the Biodiversity Action Plan

The Drainage District

The Black Sluice Internal Drainage Board has an operational area covering 35,000 hectares (112,000 acres) of low lying fenland south west of Boston. The area is protected from flooding by the sea defences of the Haven and the Wash, the banks of the River Witham on the north west boundary and the Bourne Eau and River Glen banks on the southern boundary. The South Forty Foot Drain runs through the centre of the District and the southern reaches and the high level carrier drains are embanked to prevent flooding to the fen areas.

A greater part of the area is below high tide level, and the Board maintains thirty four pumping stations to control the water levels in the low lying Fens. The Board has a supervisory role in all aspects relating to the drainage of land.

Whilst the Board has powers to undertake works on any non main river watercourse within its drainage District, direct maintenance is limited to 480 miles (700km) of watercourses designated as "Board's Drains". The responsibility for maintenance of the remaining watercourses in the area, normally called dykes and ditches, rests with the landowner known in law as the "riparian owner".

Statutory Obligations

The Land Drainage Act 1991, as amended by the Land Drainage Act 1994, places a duty on Internal Drainage Boards (IDBs) with respect to the environment and recreation. In simple terms, the amended act requires IDBs, in so far as may be consistent with their functions, to further the conservation of flora, fauna and geological or physiographical features of special interest, and to have regard for protecting sites of archaeological or historical interest.

IDBs should also take into account the effect that any proposals they wish to promote could have on the beauty or amenity of any rural or urban area, or on any such flora, fauna, features, buildings, sites or objects in that area.

The Environment Impact Assessment (Land Drainage Improvement Works Regulations 1999 (SI 1999 No 1783) and 2005 (2 & 3) requires IDBs to undertake an assessment of the impact on the environment of projects likely to have significant effects and under the Countryside & Rights of Way Act 2000, IDBs must consult English Nature on proposed works or operations if these impact on the interest features of Sites of Special Scientific Interest (SSSI's).

Under the habitat Regulations 1994, IDBs are required to consider the likely significant effect of their plans or projects on European designated sites, which in the case of the Black Sluice IDB would be the Wash area Special Area of Conservation (SAC). It is however unlikely that the nature, scale and timing of operations undertaken by the Board would impact on this site.

IDBs are Section 28G Authorities under the Countryside Rights of Way (CROW) Act and will comply with the requirements of this Act.

Sites of Environmental and Conservation Interest

Within or immediately adjacent to the Black Sluice IDB District, the following sites have been designated for their environmental and conservation interest.

Special Area of Conservation:

Sites of Special Scientific Interest:

The Board

The Board consists of elected members representing Agricultural ratepayers and members appointed by District Councils. The Board agrees the policy and operation of the Board's workforce and is advised by the officers employed by the Board.

The Board has an Environmental Committee which meets on a regular basis with the following terms of reference:-

1.     To monitor the Board's performance in relation to the Lincolnshire Biodiversity Action Plan and Government's Environmental Targets.

2.     To promote best practice through employee training and awareness.

3.     To inform the public of the Board's commitment to environmental issues.

4.     To promote initiatives, within watercourses maintained by the Board under statutory powers, that result in a meaningful environmental gain.

The Board is achieving the aims in the following ways:-


o    A programme of surveying watercourses is being undertaken.

o    The workforce record Biodiversity Action Plan species seen during their work.

Best Practice

o    An agreed method of maintenance of drainage channels is followed by the workforce.

o    Regular training courses are arranged.

Informing the Public

o    Publications.

o    Exhibitions and Shows.

o    Website.

Environmental Gain

o    Improvement to watercourses.

o    Resisting unnecessary culverting of drainage channels.

Routine Maintenance Operations

Regular maintenance of the Board's drains is essential for land drainage and flood defence and for maintaining the biodiversity of the watercourse system. The maintenance work is carried out sympathetically and with nature conservation interests kept firmly in mind.

Maintenance specifications provide guidance on the appropriate standards to be achieved, taking into consideration the operational needs of the catchment served, the impact of the work on the conservation interest of the watercourse and the natural habitats provided by the watercourse. In rural catchments watercourses serving primarily agricultural needs offer the greatest scope for effecting environmental gain and the specifications adopted for these watercourses reflect the advantages to the environment, to conservation interests and to the Board in a reduced level of maintenance.

The Board pays particular attention to the fact that many drains provide habitat for water voles, and these habitats are protected under Schedule 5 of the Wildlife and Countryside Act 1981. The Board is recording locations where water vole habitat has been found so that the maintenance of watercourses at these locations can be undertaken without damaging or obstructing access to their burrows.

Annual Operations

Bank vegetation maintenance and in-channel weed clearance will be carried out on an annual basis in the Board's drainage channels. Most watercourses will only be cut once each year. The work will commence mid-way through July and the Board will aim to have completed the greater part of the work by the end of October. In most drains the bank on which the machinery will operate will be flail mown to allow the drivers of the machinery to see where they are operating. The bed of the drain will be cleared of weed growth to increase conveyance, reduce water levels, and protect the functioning of structures which may otherwise become blocked. In most cases the far bank of the drainage channel will remain uncut.

In larger watercourses fringes of uncut vegetation at the water’s edge will be left as this helps prevent erosion to the banks and provides both food and shelter for small mammals and birds.

In a small number of specified drainage channels which protect large numbers of properties, one bank will be continuously flail mown from March until September to allow the channel to be cleared early in June to minimise the flood risk to these properties.

The Board uses herbicides in a limited number of situations where the use of mechanical control of weed growth would be more environmentally invasive.

The work will be carried out in accordance with all the regulations by trained members of the workforce or contractors after approval has been given by the Environment Agency.

Desilting Operations

Desilting operations are most often undertaken during the winter months. In most cases the work needs to be carried out every ten years, and involves the removal of silt from the bed of the drain. Additional work to remove material from the banks is only undertaken when the banks have become very steep or where slips have occurred. The need for works is entirely related to flood defence needs so as to maintain capacity, stabilise banks and to maintain conveyance. Reforming (removing firm material) and regrading (bed and banks) requires a site-specific approach, always involving an ecologist, often involving River Corridor Survey and sometimes involving an Environmental Impact Assessment. Protection of existing ecological interest is paramount in desilting operations and riffles, areas of cobbles and gravels will be left untouched or replaced. One working bank only will normally be used, being chosen for ease of access, sensitivity of vegetation present, adjacent land use including presence of crops and the need to minimise works along the channel. Variation in the long-section as well as the cross-section of a watercourse will be an objective. Enhancements will be considered where possible and working undertaken wherever possible to mimic natural fluvial processes. Spoil may be incorporated into adjacent land via thin spreading, usually within 2-10m of the watercourse. On pasture, spoil may be placed into a trench and then covered with the topsoil.

Tree Maintenance

Tree maintenance may be necessary to provide access to a channel for maintenance work, to remove the risk of trees falling into the channel or to remove low-growing limbs that accumulate floating wrack and thus reduce conveyance. The Board's practice is to retain old trees and manage as few trees as possible, as lightly as possible. Felling is the last resort. When gaining access for channel works it may be possible to leave a 'tunnel' within overhanging trees. If material must be burned it will be done away from important or vulnerable areas. Where acceptable, it may be heaped above flood levels, to form "habitat piles" for invertebrates and nesting birds. Pollarding may be undertaken in appropriate areas between November and March following assessment for presence of bats. Where access is needed over hedges, then coppicing may be undertaken. A rotation of coppicing along a river helps maintain various stages of tree growth and refugia and cover for wildlife.

Water Level Management Plans

Water Level Maintenance Plans (WLMP's) provide a means by which the water level requirements for a range of activities in a particular area, including agriculture, flood defence and land drainage, conservation, amenity and recreation can be formalised, and where possible, integrated.

A formal WLMP has been completed for the Horbling Catchment to comply with the requirement that these should be completed for all areas where there is an SSSI within the catchment. In other catchments informal plans exist which raise water levels during the summer months to provide both conservation and agricultural benefits.

Conservation Objectives

The Black Sluice Internal Drainage Board will:-

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