West of England Woodland Opportunity Study

Data Source:

Ordnance Survey OpenRoad

Ordnance Survey OpenMap

Ordnance Survey OpenRivers

National Grid

BEIS

Aerial imagery

Assumption:

For woodland planting of all scales, the following physical constraints preventing woodland planting were treated as constraints:

• Buildings
• Major gas pipelines +20m buffer
• Consented and operational solar farms + 20m buffer
• Consented and operational wind farms + 50m buffer
• Water courses and bodies

For existing wind developments, it was assumed these were of notional medium scale tip height and occupied a 5 x 3 rotor diameter oval spacing, with the major axis of the oval oriented towards the prevailing wind direction, taken to be south-west (see turbine spacing below). (To mitigate impacts on the productivity of wind turbines located close to one another caused by wind turbulence, it is standard practice for developers to maintain an oval of separation between turbines that is equal to 5 times the turbine rotor diameter (the cross sectional dimension of the circle swept by the rotating blades) on the long axis, and 3 times the rotor diameter on the short axis.)

For small-medium to large sized woodland, the following additional physical constraints preventing woodland planting, were also treated as constraints:

• Roads
• Railways
• Major transmission lines +80m buffer
• Airports and airfields
• Water courses defined by linear datasets

Justification:

Physical features were excluded that prevent woodland planting.

For small-medium scale to large woodlands, an 80m buffer along major transmission lines (40m each side) was treated as a constraint to woodland planting. This acts as a safety buffer to enable falling tree clearance. National Grid do not provide rules on required buffer distances, but do provide guidance on clearance distances dependent on transmission pole and tree heights. This buffer was therefore applied using a pragmatic approach based on industry knowledge.

Small scale woodlands have the potential to be sited beneath major electricity transmission lines and therefore these were not treated as a constraint for small scale woodland planting. Further study would be required to make consideration of transmission lines operated by the local DNO National Grid (Formerly Western Power Distribution).

For all woodland scales, a 20m buffer along major gas pipelines (10m each side) was treated as a constraint to woodland planting. This acts as a safety buffer to prevent root damage to pipelines. This is in line with National Grid guidance on tree planting restrictions on pipelines. For security reasons National Grid do not provide the exact locations of the pipelines but a buffered dataset of approximately 25m in width. The 20m buffer was applied in addition to this current buffer.

It is noted that regionally operated transmission lines and additional pipelines and underground utilities may also require safety buffers to restrict planting. However, this is beyond the scope of this study and would require separate site-specific assessment.

A 20m buffer around existing and consented solar farms was treated as a constraint. This accounts for potential shading impacts on solar output.

A 50m buffer around existing and consented wind farms was treated as a constraint to account of standard practice endorsed by Natural England guidance set out in ‘TIN051’. A 50m horizontal buffer is a reasonable proxy clearance for the purposes of a strategic study given unknowns concerning tree height and turbine dimensions. A 50m buffer cannot be applied to all linear habitat features and individual trees due to a lack of data for a study of this scale.

Note: Only line data for roads was available and in order to create a footprint from the road centre, it was assumed that single carriageways are 10m in width, dual carriageways 20m and motorways 30m. In order to create a footprint from the railway centrelines data, it was assumed that railways are 15m in width. OS surface water area data includes waterways of a minimum of 2m width approximately.

OS Rivers and surface water line data are line data, and so a 1m buffer was applied to approximate a footprint of smaller waterways. In addition, many drains are included in the OS Survey OpenMap Local surface water area data that may not be a constraint to woodland planting. However,he majority of these are also covered by priority habitats, and therefore are constraints to woodland planting in this way.. Further site-specific study may therefore be required in relation to field drains when planning woodland planting.

Small sized woodlands (<5ha) including linear planting such as hedgerows with hedgerow trees have the potential to be integrated adjacent to linear physical features (such as roads, railways and water courses). In order to prevent such potentially suitable locations for this type of planting being identified, these linear datasets were not treated as constraints to small scale planting.

In addition, small sized woodlands have the potential to be integrated in the corners of airports and airfields and in conjunction with hedgerows and therefore planting in such locations may not be inappropriate.

The suitability of any scale of woodland adjacent to these types of physical features in specific locations requires detailed site-specific assessment and liaison with local stakeholders to ensure their suitability. For example, liaising with the Canal and River Trust regarding the suitability of riverside woodland to increase river shading to benefit fishing.

Data Source:

• South Gloucestershire Council
• North Somerset Council

Assumption:

For small sized woodland, no open space is treated as constraint.

For small-medium to large sized woodland, the following designated open space types have been treated as constraints:

• South Gloucestershire Council open space over 5ha
• North Somerset Local Green Space

Justification:

Open space is protected by local policy and therefore woodland planting may be inappropriate.

However, small sized woodlands (<5ha) have the potential to be integrated alongside open spaces, in the corners of fields and in conjunction with hedgerows. Therefore, their impact on designated open space would be minimal and planting on this scale may be appropriate.

Data Source:

• South Gloucestershire Council
• North Somerset Council

Assumption:

For small sized woodland, no settlements were treated as a constraint.

For small-medium to large sized woodland, the following settlement boundaries have been treated as constraints:

• South Gloucestershire CS5 settlement boundary
• North Somerset settlement boundaries

Justification:

Areas of unconstrained land within urban areas mainly comprise of residential private gardens and other small pockets of green space, unsuitable for small-medium to large woodland creation. However, such land may be suitable for small sized woodland.

The suitability of any scale woodland within or adjacent to urban settlements would require more detailed site-specific assessment and liaison with locally knowledgeable stakeholders to ensure sites are suitable.

Data Source:

• South Gloucestershire Council

Assumption:

Site allocations from the adopted local plans were treated as constraints

The following South Gloucestershire planning datasets were treated as constraints: live large sites, large pending sites and S106 sites. 

Justification:

Generally, these allocations are unsuitable for significant woodland creation, although there may be some potential for planting on undeveloped land/open space. Identification of this potential would require site-specific assessment, which is beyond the scope of this study.

The national Agricultural Land Classification dataset is dated as 1988 and so will not reflect development on Grade 1 or 2 land since this date. Therefore, this constraint will not be present around many urban areas where development has occurred since 1988.

Data Source:

• Natural England

Assumption:

For small sized woodland, no agricultural land is treated as a constraint.

For small-medium to large sized woodland:

• Land classified as Agricultural land grades 1 and 2 were treated as constraints

Justification:

Excellent quality (Grade 1) and very good quality (Grade 2) agricultural land has the potential to deliver the highest crop yields and as such woodland planting on this land is inappropriate for woodlands above 5ha.

Small sized woodlands (<5ha) have the potential to be integrated alongside crops in the corners of fields and in conjunction with hedgerows, including as part of agro-forestry schemes. Therefore, impact on agricultural land loss would be minimal and planting on Grade 1 and 2 land may not be inappropriate. However, further site-based assessment and consideration of planting density refinements would be required to ensure sites are suitable and to ensure opportunities are taken for agri-environmental gains.

Good quality agricultural land (Grade 3a) is capable of consistently producing moderate to high yields of some arable crops and cereals, and as such, woodland planting on this land may be less appropriate. However, there is no full dataset of Grade 3a/3b agricultural land covering the study area. Moreover, the Forestry Commission advise Grade 3a would be of up to only low sensitivity to woodland creation. As such Grade 3 land is not considered a constraint to woodland planting.

Data Source:

• Natural England: Peaty Soils Location

Assumption:

Areas of deep peaty soil were treated as constraints

Justification:

Peat soils are capable of absorbing and storing large amounts of carbon, but if disturbed, peaty soils can release carbon. Woodland planting on these soils would be inappropriate and as such it is considered a constraint.

Data Source:

• CEH Land Cover Map 2021

Assumption:

Land cover types not suitable for woodland planting were treated as constraints:

• Fen, Marsh, and Swamp
• Inland rock
• Littoral rock
• Littoral sediment
• Saltmarsh

Justification:

These land cover types would not be suitable for woodland planting.

Note: Bog; Supra-littoral rock and Supra-littoral sediment would have also been excluded but these land cover types are not present within the study area.

The following land uses were not treated as constraints as tree planting may be feasible in these locations:

• Acid grassland (none present in study area)
• Arable and horticulture
• Calcareous grassland
• Heather
• Heather grassland (none present in study area)
• Improved grassland
• Neutral grassland

The suitability of these land cover types for woodland planting would however require further site-specific assessment, for example to ensure that planting would not threaten undesignated land that is functionally linked to designated Natura 2000 sites, and that planting density refinements are considered on agricultural land to ensure opportunities are taken for agri-environmental gains.

In addition, the following categories were not excluded as these were considered using other more detailed datasets:

• Broadleaved woodland
• Coniferous woodland
• Freshwater
• Saltwater
• Suburban
• Urban