Ditch BNG Units
Medium
Watercourse
Trusted by Developers and Landowners
What are Ditches?
Ditches are linear watercourses, usually artificial in origin, dug for drainage or water management. Many are simple farmland drains, but others have developed rich communities of aquatic plants, invertebrates, amphibians, birds, and mammals. Their biodiversity value depends on water quality, vegetation, and management.
Why It Matters for BNG
Ditches provide linear aquatic units essential for meeting metric requirements in lowland landscapes. Well managed ditches support aquatic plants, amphibians, and invertebrates.
Routine ditch management, water quality protection and vegetation control enable landowners to produce linear BNG units with limited change to current practice.
Where Do They Occur?
• Across lowland agricultural landscapes, especially in arable and grazing systems
• In lowland floodplains, grazing marshes, and fenland
• Along field boundaries, tracks, and roadsides
• As part of historic drainage systems in wet regions
How New Ditches Are Created
Inputs
• Excavate channels to hold water for much of the year
• Profile banks with gradual slopes to allow marginal plants to establish
• Maintain water supply from groundwater or surface inflow
• Avoid lining or over-engineering which prevents colonisation
Management
• Protect banks from livestock poaching with fencing or buffer strips
• Manage vegetation and silt on a rotational basis, leaving some sections undisturbed
• Avoid excessive dredging or clearance which removes all plant life
Landscape
• Position new ditches where they connect into wider ditch networks or semi-natural wetlands
• Maintain uncultivated margins alongside to buffer against fertilisers and pesticides
• Link ditches to hedgerows or grass strips to provide combined habitat corridors
How Existing Ditches Are Improved
Inputs
• Widen or restore buffer strips to reduce nutrient enrichment
• Repair eroded banks and exclude livestock where necessary
• Control invasive non-native plants and animals
Management
• Switch from annual clearance to rotational management to allow vegetation to persist
• Maintain sufficient water levels through the summer to support aquatic species
• Encourage marginal vegetation by leaving uncut stretches each year
Landscape
• Restore connectivity by linking broken sections into longer networks
• Integrate ditches with hedgerows, grassland, or field margins for added ecological value
• Enhance wetland character by diversifying depth and flow
Target Condition
Ditches in Good condition will show:
• Clear water of good quality, with low turbidity and no signs of pollution
• A range of aquatic plants, ideally more than 10 emergent, floating, or submerged species in a 20m length
• Little or no filamentous algae or duckweed (under 10% cover)
• Marginal vegetation along more than 75% of the length
• Less than 5% physical damage to banks and channel
• Sufficient summer water depth (c. 50 cm in minor ditches, 1 m in main drains)
• Less than 10% heavy shading
• Absence of non-native invasive plants or animals
The BNG Value of Ditches
• Distinctiveness: Medium
• Condition potential: Strong, with scope to support diverse aquatic and marginal flora
• Connectivity: Provide vital linear corridors across farmed landscapes
• Climate services: Store water, slow run-off, and trap sediments, contributing to flood regulation
• Time to target condition: 5–15 years depending on water quality and management
Species Typical of Ditches
🌸 Aquatic and marginal plants
• Water violet (Hottonia palustris)
• Pondweeds (Potamogeton spp.)
• Yellow flag iris (Iris pseudacorus)
• Reed sweet-grass (Glyceria maxima)
• Common reed (Phragmites australis)
🐝 Invertebrates
• Dragonflies (e.g. Aeshna mixta)
• Diving beetles (Dytiscidae)
• Water boatmen (Corixidae)
🐇 Mammals
• Water vole (Arvicola amphibius)
🐦 Birds
• Snipe (Gallinago gallinago)
• Reed bunting (Emberiza schoeniclus)
• Pied wagtail (Motacilla alba)
• Mallard (Anas platyrhynchos)
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Frequently Asked Questions
What are Ditches?
Linear, artificially excavated water channels, often for drainage purposes. They can be important habitats for amphibians and aquatic invertebrates, especially in low-lying areas.
How is BNG measured here?
Measured in linear metres. Condition is assessed by the quality of the aquatic vegetation, the profile of the ditch, and the management regime (e.g., rotational de-silting).
How can I achieve BNG?
Enhancement by managing the clearance cycle to retain some established vegetation (rotational clearing), ensuring varied bank profiles, and reducing nutrient inputs from adjacent land.
What is the BNG target condition?
A Good condition involves clear water, diverse aquatic vegetation, and a soft, shallow bank profile, managed on a long rotation to allow wildlife to persist.
What management is required?
Long-term rotational de-silting and vegetation clearance (ideally one side at a time) to maintain flow while ensuring a continuous habitat for species.
Exploring Other Habitats?
Rural Tree
Rural trees are individual trees located in the open countryside that do not form part of woodland, hedgerow or wood-pasture habitats. They include isolated field trees, parkland trees, scattered trees in paddocks, and trees along rural roadsides or watercourses where they are not part of a continuous linear feature.
Ancient and veteran trees in rural locations are also recorded under this habitat type and are additionally flagged as irreplaceable habitat, meaning impacts should be avoided wherever possible.
Upland Mixed Ashwood
Upland mixed ashwoods are species-rich broadleaved woodlands found on base-rich soils in upland landscapes. They are typically dominated by ash, though locally oak, birch, wych elm, rowan, small-leaved lime or hazel may be prominent depending on site conditions.
These woodlands often develop on limestone and other calcareous substrates, including steep slopes, ravines, flushes and rocky outcrops. Many upland mixed ashwoods are ancient woodland, while others represent long-established secondary woodland that retains strong ecological continuity.
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Ponds (Non-Priority Habitat)
Non-priority ponds are small standing waterbodies, generally up to two hectares in size, that do not meet the priority pond criteria but still function as semi-natural freshwater habitats. Non-priority ponds include many farm ponds, estate ponds, attenuation ponds with natural features, and older field ponds that support aquatic and marginal vegetation but lack the exceptional species assemblages required for priority status.
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