Wet Woodland BNG Units
High
Woodland and forest
Widespread across England in floodplains, valley bottoms and poorly drained lowland sites.
Trusted by Developers and Landowners
What is Wet Woodland?
A Wet Woodland BNG Habitat is a structurally rich, water-tolerant woodland habitat found in waterlogged conditions across floodplains, stream sides, valley bottoms and areas of permanent or seasonal flush. It is dominated by moisture-loving trees including alder, willows and downy birch, which form dense canopies over poorly drained or seasonally inundated soils.
The ground flora is characteristically diverse, supporting lichens, mosses, sedges, ferns and a wide range of wetland plants. Wet woodland is strongly associated with dynamic riparian systems and often develops naturally in redundant channels, wet carr and floodplain margins.
Why It Matters for BNG
Wet Woodland generates high biodiversity units due to its high distinctiveness and condition multiplier. Its strong BNG value makes it a credible and well-evidenced option for off-site habitat delivery, particularly on floodplain and riparian sites.
Learn more about BNG for landowners →
Where You'll Find It
Wet Woodland occurs in low-lying and floodplain landscapes, along streams and rivers, in valley bottoms, fens and poorly drained basins. It may also develop naturally on former agricultural land where drainage has ceased. Distribution is closely linked to groundwater levels and seasonal flooding patterns.
Soil & Site Requirements
Wet Woodland requires poorly drained or periodically flooded soils. Natural hydrology must be maintained, with groundwater or surface water close to the soil surface. Drainage, culverting or altered flood regimes can rapidly degrade habitat quality.
How New Wet Woodland Is Created
Inputs
• Restore or maintain natural water levels
• Plant water-tolerant native tree species where needed Avoid drainage and soil improvement
• Protect young trees from browsing
Management
• Allow natural regeneration where hydrology supports it
• Avoid large-scale soil disturbance
• Retain fallen timber and natural debris
• Prevent nutrient enrichment
Landscape
• Position within floodplains or low-lying basins
• Link to rivers, streams or wet grassland
• Maintain connectivity with other wet habitats
How Existing Wet Woodland Is Improved
Inputs
• Block artificial drains where appropriate
• Remove invasive shrubs
• Improve native species dominance
Management
• Reduce grazing pressure to allow regeneration
• Retain standing and fallen deadwood• Maintain varied age structure
• Protect saturated soils from compaction
Landscape
• Buffer woodland from adjacent agricultural runoff
• Restore floodplain connectivity
• Increase block size where feasible
Target Condition
Wet woodland in defined BNG condition should:
• Be dominated by native water-tolerant tree species
• Contain multiple age classes
• Show active regeneration
• Retain standing and fallen deadwood
• Support characteristic wet woodland ground flora
• Have limited invasive species cover
• Maintain natural hydrological function
The BNG Value of Wet Woodland
• Distinctiveness: High
• Condition Potential: Strong uplift potential through hydrological restoration and regeneration
• Restoration Pathway: Creation feasible where hydrology is restored; enhancement often more reliable
• Strategic Value: Critical floodplain woodland linking rivers, wetlands and lowland woodland networks
Species Typical of Wet Woodland
Canopy or Primary Layer
• Alder (Alnus glutinosa)
• Willow
• Downy birch (Betula pubescens)
Shrub or Secondary Layer
• Hazel (Corylus avellana)
• Guelder rose (Viburnum opulus)
• Elder
Ground Flora or Understorey
• Sedges
• Mosses
• Ferns
• Marsh herbs and rushes
Frequently Asked Questions
What is Wet Woodland?
A Wet Woodland BNG Habitat is a high distinctiveness priority habitat that is dominated by water-tolerant trees such as alder, willows and downy birch.
How is BNG measured here?
Condition is assessed across 13 scored criteria covering age structure, native species diversity, regeneration, deadwood, ground flora, vertical structure, veteran trees, herbivore damage, invasive species and disturbance.
How can I achieve BNG?
Wet woodland can deliver BNG either through creating new stands on marginal or poorly drained land, or by improving the condition of existing woodland through structural management, deadwood retention and control of invasives and browsing.
What is the BNG target condition?
Good condition requires high native species diversity, multi-layered structure, abundant deadwood, active regeneration, characteristic NVC ground flora and low levels of browsing, invasives and disturbance.
What management is required?
Long-term management focuses on maintaining structural complexity, retaining deadwood and veteran features, controlling deer and invasive species, protecting hydrological conditions and avoiding soil disturbance in the wet zone. Monitoring of regeneration and deadwood should be carried out on a five-to-ten-year cycle.
Exploring Other Habitats?
Arable Field Margins Pollen and Nectar
Arable field margins pollen and nectar are grass margins around arable fields sown with wildflowers and legumes managed specifically to provide pollen and nectar resources for invertebrates. The mix must include at least four nectar-rich flowering species and the margin is kept low-input and rotationally cut to maintain flowering through the season. The arable field must remain in a crop rotation including an arable crop.
Unlike wild bird seed margins, the management objective here is flowering continuity for pollinators rather than seed retention for birds. This habitat type sits within the Cropland broad habitat in the BNG metric and is classified separately from tussocky margins, cultivated margins and game bird mix.
Arable Field Margins Game Bird Mix
Arable field margins game bird mix are margins, strips, blocks or corners around arable fields sown with wild bird cover crops and left unharvested over winter so that seed produced by the plants remains available to farmland wildlife. The arable field must be in a crop rotation that includes an arable crop, such as wheat, barley, maize or oats, even if in certain years the field is in temporary grass, set-aside or fallow.
Mixes typically combine seed-bearing cereals, brassicas and oil-rich crops to provide food through the winter hungry gap and standing cover for gamebirds and declining farmland bird species.
Arable Field Margins Cultivated Annually
Arable field margins cultivated annually are strips along the edges of arable fields, typically 2–12 metres wide, managed under a low-input regime to support annual arable plants. They are lightly cultivated each year, usually in late summer or autumn, without herbicide or fertiliser, creating the open, disturbed soil conditions that annual arable flora requires to germinate.
Ready to buy your units?
Easily buy your BNG units online today to ensure compliance and positive environmental impact.