Guidance note: SuDS and Biodiversity

Schedule 3(2) of the Flood and Water Management Act 2010 defines sustainable drainage as: "managing rainwater with the aim of: reducing damage from flooding; improving water quality; protecting and improving the environment; protecting health and safety; and ensuring the stability and durability of drainage systems".

The Act requires that all new developments of one or more dwellings, or where the hard construction area is 100m2 or greater, require on-site surface water to be managed by SuDS. The local authority in its role as SuDS Approving Body (SAB) manages the process of approval and adoption of SuDS.

The Sustainable Drainage Standards for Wales recognise the opportunities presented by SuDS to maintain and enhance biodiversity and ecosystem resilience. Standard S5 - Biodiversity: "addresses the design of SuDS to ensure that, where possible, they create ecologically rich green and blue corridors in developments and enrich biodiversity value by linking networks of habitats and ecosystems together. Biodiversity should be considered at the early design stage of a development to ensure the potential benefits are maximised."

How can SuDS add biodiversity value?

If implemented well, SuDS can:

• Enhance existing habitats and species in the local area;
• Provide multi-functional green infrastructure;
• Help with delivering local biodiversity objectives;
• Connect habitats, thereby supporting wider ecosystem resilience and climate change adaptability; and
• Create new, diverse, self-sustaining local ecosystems.

SuDS should consider the species that may already be present on or near a site. For example, consider the needs of otters, water voles, reptiles and amphibians. Riparian woodland/thickets/grassland should be retained or created to provide refuge for wildlife. Incorporate flowering native species to encourage pollinators, which will in turn provide a food source for birds, bats and other small mammals.

These documents contain best practice and guidance regarding SuDS and biodiversity:

• Construction Industry Research and Information Association (CIRIA) SuDS Manual 2015:
  o Chapter 6 Designing for Biodiversity
  o Chapter 29 Landscape
• Royal Society for the Protection of Birds (RSBP) and World Wetlands Trust (WWT) Sustainable Drainage Systems - Maximising the potential for people and wildlife, A guide for local authorities and developers
• Freshwater Habitats Trust The Ponds Creation Toolkit
• Scottish Environment Protection Agency (SEPA) Guidance on good practice in the management and creations of small water bodies in Scotland

Native species that may be suitable for SuDS schemes

Shrubs:

• Dogwood (Cornus sanguinea)
• Guelder rose (Viburnum opulus)
• Willow (Salix spp.)
• Broom (Cytisus scoparius)
• Alder buckthorn (Frangula alnus)

Climbers:

• Ivy (Hedera helix)
• Honeysuckle (Lonicera periclymenum)
• Dog rose (Rosa canina)

Perennials:

• Hemp-agrimony (Eupatorium cannabinum)
• Pendulous sedge (Carex pendula)
• Flowering rush (Butomus umbellatus)
• Royal fern (Osmunda regalis)
• Yarrow (Achillea millefolium)
• Bugle (Ajuga reptans)
• Knapweed (Centaurea nigra)
• Cowslip (Primula veris)
• Self-heal (Prunella vulgaris)
• Thyme (Thymus polytrichus)
• Ox-eye daisy (Leucanthemum vulgare)
• Common birds-foot trefoil (Lotus corniculatus)
• Devil's-bit scabious (Succisa pratensis)
• Ragged robin (Silene flos-cuculi)
• Cuckoo flower (Cardamine pratensis)

Aquatic/marignal plants:

• Yellow flag iris (Iris pseudacorus)
• Purple loosestrife (Lythrum salicaria)
• Marsh woundwort (Stachys palustris)
• Gipsywort (Lycopus europaeus)
• Brooklime (Veronica beccabunga)
• Marsh marigold (Caltha palustris)
• Meadowsweet (Filipendula ulmaria)
• Water mint (Mentha aquatica)
• Water forget-me-not (Myosotis scorpioides)
• Frogbit (Hydrocharis morsus ranae)
• Water crowfoot (Ranunculus aquatilis)

Invasive species

Invasive non-native species (INNS) should never be planted in SuDS (or other landscaping schemes), as they are very damaging to biodiversity and it is illegal to grow or otherwise cause them to spread in the wild. The following are some examples of aquatic and terrestrial INNS:

• Montbretia (Crocosmia x crocosmiiflora)
• Three-cornered garlic (Allium triquetrum)
• Few-flowered leek (Allium paradoxum)
• Japanese rose (Rosa rugosa)
• Himalayan balsam (Impatiens glandulifera)
• Japanese knotweed (Reynoutria japonica)
• Rhododendron (Rhododendron ponticum and Rhododendron ponticum x Rhododendron maximum)
• Yellow azalea (Rhododendron luteum)
• Floating Pennywort (Hydrocotyle ranunculoides)
• Parrot's Feather (Myriophyllum aquaticum)
• New Zealand Pigmyweed also known as Australian Swamp stonecrop (Crassula helmsii)
• Water primrose (Ludwigia grandiflora and Ludwigia uruguayensis)
• Floating water primrose (Ludwigia peploides)
• Water fern (Azolla filiculoides)
• Curly waterweed (Lagarosiphon major)
• Waterweeds (Elodea spp.)
• Giant rhubarb (Gunnera tinctoria)
• Water hyacinth (Eichhornia crassipes)
• Fanwort (Cabomba caroliniana)
• Water lettuce (Pistia stratiotes)
• Broadleaved arrowhead (Sagittaria latifolia)
• Giant salvinia (Salvinia molesta)