National Planning Policy Framework and the Challenge of Street Trees

29th November 2022

National Planning Policy Framework and the Challenge of Street Trees

The current National Planning Policy Framework (NPPF 2021) recognises the importance of tree-lined streets and their extensive environmental benefits. Street trees have long been a key feature of the urban environment and play a vital role in defining the character of towns and cities. Trees provide invaluable ecological benefits to our towns and cities by providing habitats, absorbing carbon dioxide and releasing oxygen. For these reasons, street trees support the requirement to conserve and enhance the natural environment as set out in the National Planning Policy Framework.

Everyone recognises the role of trees in mitigating climate change but, making street trees a part of new or existing urban environments can be a challenge. At IDP we seek to challenge this by involving all the consultants in our design team. We recognise that planning for street trees affects the work of landscape architects, drainage engineers, highways engineers, utilities providers, architects and planners. Making space for them also requires inputs from regulators and authorities at both National and Local level.

Street Trees
Tree lined vs non-tree lined streets. Tree pit image supplied by GreenBlue Urban.

NPPF 2021 and the Natural Environment

In July 2021 the Government updated the National Planning Policy Framework (NPPF) to include the requirement that “new streets are tree-lined” (paragraph 131). Now, more than ever, we need a collaborative approach from all concerned. We need to reach a shared understanding of the work involved to make trees a sustainable part of our future streets. Our focus must be on successfully planting and sustaining new street trees, alongside plans that will keep these trees healthy. We must recognise the challenges that affect the longevity of proposed street trees and work with all stakeholders to maximise the benefits and minimise the difficulties trees can create.

The wording of NPPF Paragraph 131 leaves some flexibility in the regulations regarding what constitutes “tree-lined” and where exceptions can be made. These matters are being argued out by Local Authorities and planning applicants across the country. It will take time to reach something close to a consensus on this topic, but IDP is listening closely to these discussions and we will make sure we are ready to respond when these debates conclude. The outcome of these discussions will steer future planning decisions and we want to be sure that our work for clients supports them in their service to the environment and community.

Planning for Street Trees – What will Work Best in the National Planning Policy Framework 2021?

Although elements remain uncertain, the earlier the aspirations for a particular site in relation to street trees are set out, the better. This applies to many things in planning and, in every instance, we find it helpful to pay attention to macro and micro factors. We review a number of important factors with our clients at an early stage. This helps ensure their plans to include street trees are successful.

5 factors to determine when planning for street trees

  1. tree type
  2. canopy form
  3. mature height
  4. soil volume requirements
  5. proximity to foundations

All the above factors have an impact on land taken within a site. By understanding this at an early stage, we can avoid complications once we begin the more detailed stages of planning. What tends to happen is that the early visions of tree-lined streets intended at the outset of a design are whittled down. This often occurs as the focus shifts to the pressure to deliver more housing numbers and space becomes more pressured. We regularly see that the practicalities of delivering street trees alongside highways, services and so on results in fewer trees being planted and they are more dispersed as a result.

Improvement in Regulations

In order to meet the challenge of tree lined streets, we need new standard street typologies. More research is needed as highways authorities seek out and explore new methods of construction that they can adopt. We also need new in-depth guidance from the National House Building Council (NHBC) that will give designers more flexibility in terms of tree selection. Our understanding is that new guidance is forthcoming and this is not before time.

To allow developers to meet the aspirations of NPPF 2021, highways authorities need to collaborate with designers to meet this new challenge. This means they must stop refusing to adopt trees within adopted verges. Stakeholders need to investigate new construction methods that can protect the highway construction while supporting healthy street-trees. This includes delivering the requisite uncompacted topsoil volume to ensure that trees thrive and deliver on their environmental and amenity benefits.

The current NHBC guidance needs to be updated to reflect the greater variety of street trees that are now available on the market. For example, trees such as Acer campestre ‘Streetwise’ have been cultivated by nurseries for the specifically for streets and the urban environment. This is essential for us to minimise the impact of climate change on our natural environment and meet the standards that are likely to emerge from NPPF 2021.

Next Steps in Implementing the National Planning Policy Framework

We are keen to play our part in finding a way through these challenges. As a result, IDPs Urban Design and Landscape Teams sat down in a recent design workshop to look at how these issues can be addressed and progressed. The discussion explored options that will produce positive outcomes for all parties concerned. The general consensus was that parameters surrounding street tree provision should be set out as early as possible in the planning stages. The aim is to safeguard their delivery through Reserved Matters and the technical design stages. This echoes our own approach with clients and we are optimistic we can continue to take trees through from design to implementation over the years to come.

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