2.67 Developments can provide a mixture of public, communal and private outdoor amenity space. The type of amenity space proposed should be suited to the use of the proposal and the site context.

2.68 Large residential developments over 50 dwellings should provide communal or public space such as garden squares or open spaces in addition to private amenity, particularly in areas where the access to or quality of open spaces has been identified as deficient – see Fig.60 overleaf.

2.69 Where the conversion of a building into multiple residential occupancy is proposed, the applicant should demonstrate how the requirement for communal amenity for all residents will be met.

2.70 Outdoor amenity space should be considered from the outset and not be made up of leftover spaces. Calculations of amenity space must not include vehicle parking areas or storage areas for waste or other items.

2.71 Proposed private amenity space should meet the relevant criteria in Fig.59 to be considered fit for purpose.

2.72 The suitability of amenity space will be assessed on a case-by-case basis taking account of both the quantum and quality of space provided.

2.73 To demonstrate compliance with the criteria, applicants should submit relevant landscape design information as specified in D04.

2.74 Landscape plans should include measured distances from habitable room windows to boundaries and play areas.

2.75 Shared amenity spaces can help in forming close ties between residents and should be designed in a positive manner to facilitate relationships with opportunities for shared activities. Innovative approaches to fostering community such as playstreets, communal growing, outdoor cooking and dining are encouraged.

2.76 Adequate quantum and type of play space should be provided, based upon the GLA Population Yield Calculator and an assessment of local provision, filling any gaps. Further guidance on major schemes will be provided in the Technical Handbook that will form Part 2 of the Design Guide SPD.

2.77 The design of play space should apply the principles of GLA publications Expanding London’s Public Realm Design Guide, Making London Child Friendly and Play and Informal Recreation SPG.

2.78 Play space should be:

• positioned within a suitable location away from sources of pollution and ground floor windows but be connected to local facilities and well overlooked
• accessible to all with suitable features for children with impaired mobility
• safe and secure with managed opportunities for children to take risks
• mentally stimulating for children. Play spaces should incorporate natural elements where possible
• inclusive to all - spaces for older children in particular should include facilities that are attractive to girls to ensure these spaces serve all genders equally

2.79 The Council will expect that development proposals result in improvements to the ecological value of a site through appropriate enhancement measures, Biodiversity Net Gain, and urban greening.

2.80 The selection of biodiversity improvement and urban greening measures should be informed by a site’s existing ecological context and local nature recovery priorities. Applicants will be expected to demonstrate how the mitigation hierarchy set out in the Context chapter D03 has been used to make decisions on the approach to the design, layout and materials used in the development, and the appropriate biodiversity and urban greening interventions proposed.

2.81 Interventions should respond positively to opportunities and potential negative effects on protected/priority species on or near the site. Proximity to Sites of Importance for Nature Conservation (SINC) or Ancient Woodland (see Fig.61), strengthen wider ecological networks by creating local wildlife corridors, improving people’s connection and access to nature, reducing deficiencies in open space and surface flooding risks.

2.82 There is a presumption in favour of retention and enhancement over removal and replacement of natural features to meet biodiversity and greening aims. Existing features of natural value should be enhanced and incorporated into the design and layout, and connections between ecological features enhanced.

2.83 The forthcoming London Local Nature Recovery Strategy (LNRS) currently in development by the GLA and the proposed Bexley Local Nature Recovery Plan will aid applicants to identify priorities and opportunities to deliver nature recovery across the Borough.

2.84 Applicants should refer to Meet biodiversity net gain requirements: steps for developers’ guidance by DEFRA, to find out what is needed to meet the mandatory Biodiversity Net Gain (BNG) requirements. Unless a development meets an exemption to the BNG requirements, the development must provide 10% BNG on all habitats within the redline boundary.

2.85 For the purposes of BNG, biodiversity value is measured in standardised biodiversity units, using a calculator called the statutory biodiversity metric tool. The tool calculates the value of a wide range of habitat types, such as vegetated gardens, individual trees within private gardens, woodland, grassland, hedgerows, ponds and watercourses. The metric records the area of habitat in hectares. However, for individual trees, the metric uses set values based on the root protection area to represent the tree’s canopy biomass; this value is dependent on the tree diameter at breast height. Refer to the metric user guide for detailed guidance.

2.86 For major developments, an ecologist should enter information about the existing baseline and any planned development or enhancements in the statutory biodiversity metric tool.

2.87 For minor developments, the statutory biodiversity metric can be used, or a simpler version of the metric tool, called the Small Sites Metric (SSM). However, the SSM cannot be used if a priority habitat, protected site, or European protected species such as a bat is present. The information used to assess the wildlife and ecology of the site at the beginning of the project will help you determine which metric to use - see D03. If unsure, the statutory biodiversity metric is recommended.

2.88 Information on the existing habitat baseline and any post development interventions should be submitted with the application and reflected in the proposal.

2.89 The application should demonstrate that the design and layout has maximised opportunities for achieving BNG on-site. Should any offsite provision be necessary to achieve the full 10% BNG, this should be delivered as close to the application site as possible and within the borough, unless it can be demonstrated that no suitable sites are available within the area.

2.90 In addition to BNG, the introduction of artificial habitat features such as bat and bird bricks such as swift bricks, bee bricks, log piles, bug hotels, or artificial reefs, are also required by Local Plan Policy DP20 Part 1c. A range of artificial nest and roost enhancement measures should be incorporated within the design of all new building development and refurbishments across the Borough. Further detail relating to specific types of development such as those on industrial sites will be provided in the forthcoming Area Types document that will form Part 2 of the Design Guide SPD.

2.91 Residential schemes should provide at least two artificial bird nesting, bat roosting and invertebrate features for the first house; plus one bird nest, one bat roost box and one invertebrate feature for each additional residential unit, unless an alternative approach is justified. Tall buildings over 20m should also include Peregrine Falcon nest boxes. In accordance with best practice guidance such as BS 42021, the design of artificial features should be appropriate for the target species, suitable to the scale of development, in the correct location and be integrated into the building fabric.

2.92 Active management of existing or new features and habitat should be used to maximise value over the long-term.

2.93 Given the requirement to provide both Biodiversity Net Gain and Urban Greening, it is recommended that schemes use measures that achieve both aims to maximise the natural value of sites. Urban Greening for Biodiversity Net Gain: A Design Guide by the GLA and London Wildlife Trust sets out the urban greening factors for different surface coverings and their design considerations.

2.94 All major development should contribute towards London’s green infrastructure by ensuring that urban greening is incorporated into proposals during the early design stages. The Urban Greening Factor (UGF) is a tool that helps developers and designers identify how much and what type of greening they should be bringing forward as part of their proposals. Local Plan Policy DP21 requires that all major developments should have the aim of achieving a UGF score of at least 0.4 for major residential schemes and at least 0.3 for major mixed-use or commercial schemes.

2.95 For major proposals of more than 10 homes, applicants must submit a UGF plan, which is a site plan colour coded according to surface cover types with a key. The plan should be supported by a table demonstrating to officers how levels have been achieved (see Fig.63). Refer to the Urban Greening Factor LPG for information on calculating UGF scores.

2.96 For minor development, applicants are still required to set out what measures have been taken to achieve urban greening. Applicants should submit a simplified colour plan of the existing and proposed greening with a table showing how existing levels of greening have been retained. Refer to Fig.64.

2.97 When deciding the appropriate type of greening, consideration needs to be given to how the greening measure can help to address environmental issues that are specific to that location. For example, if the site is in an area that floods regularly then rain gardens could be considered or if it is next to local woodland then native trees could be used to extend green links into the site. Some types of greening carry a greater UGF value than others, with those that contribute most to nature and the environment scoring higher.

2.98 The Council will expect that designers actively seek opportunities to plant trees within the site – see D34. Collectively this approach will make a valuable contribution towards greening and will help to provide environmental corridors for wildlife. As outlined in D04, applicants should demonstrate that any new trees are appropriate to the context through their landscape submission.

2.99 Artificial lawns do not contribute towards biodiversity or urban greening, have a relatively short lifespan and are currently often not recyclable. Their use within development will generally not be considered appropriate.

2.100 Green roofs can be used to provide greening and enhance biodiversity. Design considerations for types of green roof will be included in the Technical Handbook. For further information refer to GRO Code of Best Practice for UK.

2.101 Green roofs can be designed to cater for many different needs or situations. As a priority, biodiverse green roofs should support local wildlife that are a priority in London and the local area as identified by ecology surveys and species. Due to limited biodiversity gain, sedum only roofs will be considered appropriate only if there is no other viable alternative.

2.102 Roof space may be required for energy generation. Green roofs and photovoltaic (PV) panels are mutually beneficial technologies and can be combined to create a biosolar roof.

2.103 Biosolar roofs are considered appropriate for industrial buildings given their lighter weight. It is important to explore opportunities in the early stages of the design process.

2.104 Sustainable drainage systems (SuDS) work by capturing rainfall and slowly releasing water into either an existing drainage system or directly into the ground. Bexley’s Level 1 Strategic Flood Risk Assessment (SFRA) identifies and assesses flood risks from different sources within the borough, such as surface water from rainfall. The Council has also co-produced detailed guidance titled Sustainable Drainage Design & Evaluation Guide for information on how to design and evaluate SuDS at each application stage.

2.105 The four objectives that proposed SuDS should meet as defined in the guidance are:

• quantity – manage water flow
• amenity – help form attractive spaces
• quality – prevent water pollution
• biodiversity – maximise wildlife habitats

2.106 Due to significant flooding issues throughout the borough, the Council requires development to include, where relevant:

• natural SuDS with multi-functional purposes that improve water quality, biodiversity and manage surface water
• permeable paving for all car parking areas and footpaths
• water reuse on site either for indoor or outdoor purposes with evidence of suitable use
• for development involving existing watercourses, these should be de-culverted or kept exposed and incorporated as natural features

2.107 Artificial water features such as rills in place of naturalised watercourses are unlikely to be acceptable.

2.108 Appropriate example features that can be used include:

• rain gardens – see Designing Rain Gardens - A Practical Guide by Urban Design London
• open water bodies, such as ponds
• swales and areas of open landscape planted with grasses, and drought and flood tolerant plant species
• green and blue roofs, which can either slow down or store rainwater
• planting of trees, particularly species with light foliage

2.109 Adequate provision must be made to ensure that surface water does not drain onto the highway, particularly footpaths, as this is an offence under s163 of the Highways Act 1980. Equally, any new access should be designed to ensure that highway run-off does not drain onto the development site.

2.110 Applicants should consider future maintenance and ensure easy removal and replacement if features have finite lifespans.

2.111 Drainage solutions should consider the infiltration potential of soils/geology, groundwater levels and vulnerability along with the location of Source Protection Zones (SPZs) in relation to the site. Refer to Level 7 of the Bexley Level 1 SFRA and its flood risk maps to inform SuDS suitability.

2.112 Developers must make provision for proper drainage to surface water drainage to ground, water courses or surface water sewer, avoiding drainage to foul sewer.