Wavin Spotlight

SuDS and biodiversity net gains

The government is to introduce a requirement for developers to deliver a biodiversity net gain on new housing and commercial developments. In this post we take a look at what biodiversity net gain is and what it could mean for Sustainable Drainage Systems (SuDS) and surface water management.


What is biodiversity net gain?

Quite simply, biodiversity net gain is the increase in biodiversity when measured before and after a development. Developers can work to increase the ‘biodiversity score’ when designing the development by incorporating natural spaces and using sound ecological principles including providing habitats for a range of species and providing corridors for the movement of wildlife.

How is biodiversity net gain measured?

The Defra biodiversity metric which has been developed by Natural England can be used to measure biodiversity net gain. It is a habitat based approach to determining a proxy biodiversity value. To apply the metric, a site will need to be surveyed and mapped and divided into parcels of distinct habitat types using a recognised habitat classification system. The biodiversity value of a habitat parcel is then evaluated based on area and quality which includes distinctiveness, condition, strategic significance and habitat connectivity. The metric was piloted by Defra in 2012 and has been recently improved by incorporating some of the features requested by industry experts including improved consideration of ecological connectivity, consideration of an extended range of habitats including green infrastructures and rivers and a spreadsheet-based tool to support the application of the metric in practice.

Why is biodiversity net gain so relevant now?

Following a consultation last year, the government is to introduce a requirement for developers to deliver a biodiversity net gain on new housing or commercial developments. Planning for this net gain would be necessary when granting planning permission. This means that wildlife habitats would need to be enhanced and left in a better state than they were pre-development. The plan would apply to developments currently covered by the Town and Country planning act in England. The improvements could come form a range of initiatives such as tree planting, swales or drainage ponds. In situations where such measures were not possible, developers could also be charged for habitat creation at a different location. The deadline to submit responses to the consultation is 10 February 2019.

What could biodiversity net gain mean for SuDS?

When created inline with the four pillars of SuDS (water, quantity, water quality, biodiversity and amenity), SuDS provide an effective way of both managing surface water and creating diverse habitats for wildlife. Up until now uptake of SuDS has been slow due to a lack of effective legislation and planning policy. However, a requirement for a biodiversity net gain could make incorporating SuDS into new developments a more attractive option for developers.

What additional benefits could a requirement for biodiversity net gain have?

It is well recognised that incorporating natural open spaces into developments can also play an important part in building thriving communities that contribute to the positive health and well being of the people that live there. The benefits of nature are known to include reduced stress and anxiety, improved physical health and opportunities to connect with others.

Further information

Department for Environment Food and rural affairs – Net gain consultation proposals
Natural England net gain and new housing developments creating gains for people and nature
RSPB – Sustainable Drainage Systems – maximising the potential for people and wildlife

Spotlight on drainage

This article is part of Wavin's Spotlight campaign, an initiative to promote "out of the box" thinking around the connected challenges posed by flood waters, climate change and urban development.

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