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 →
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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
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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?
Line of Trees
A Line of Trees in BNG is a row or corridor of trees forming a clear linear feature in the landscape. It is made up of individual trees spaced closely enough to create a recognisable boundary or route through farmland, estates or river corridors. These lines often follow historic field edges, green lanes or trackways and can include banks or ditches alongside them.
Some lines are simple boundary features, while others hold greater ecological value because they contain mature or veteran trees, standing deadwood, cavities and other natural features that support birds, bats and invertebrates.
Native Hedgerow
A Native Hedgerow BNG habitat is a linear woody habitat where more than 80% of the shrub and tree cover consists of native species. Structurally, native hedgerows consist of a dense shrub layer commonly dominated by species such as hawthorn, blackthorn and hazel, often with standard trees including oak or ash emerging above the canopy.
Ecologically Valuable Line of Trees
An Ecologically Valuable Line of Trees is a high-distinctiveness linear habitat consisting of a continuous or near-continuous arrangement of trees over 20 metres in length, typically less than 5 metres wide between major stems, and distinguished by structural features that support specialist wildlife. Unlike standard lines of trees, this habitat includes at least one tree with veteran characteristics or natural ecological niches such as cavities, standing or attached deadwood, ivy cover or loose bark.
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