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Trees on Development Sites

Trees on development sites may be protected by Tree Preservation Orders (TPOs) and/or by conditions attached to a planning permission. It is important that such trees are properly protected during construction.

Trees can occupy a substantial part of a site and because of their potential size can have a major effect on the planning and use of a site. Existing trees of good quality, well sited and appropriate for their surroundings will greatly enhance any new development by providing an immediate appearance of maturity, in such situations existing trees should be retained. However, if new or existing trees are poorly sited or an inappropriate size and species for their surrounding, they may become resented and burdensome to the owners and no amount of legal protection will ensure their retention and survival. To avoid such problems and to ensure a harmonious relationship between trees and buildings, careful planning is needed. Misplaced enthusiasm for the retention of inappropriate trees can create as many problems as the deliberate removal of good trees.

A tree may take a century to reach maturity, but it can be damaged or felled in only a few minutes. This damage is usually caused accidentally, because of a failure to appreciate the vulnerability of trees, particularly the root system, and how easily and unknowingly they can be damaged. Irreparable damage is frequently done to trees in the first days of contractors occupying the site.

Identifying important trees Pre-development
Early and good identification and protection of important trees on development sites is essential from the outset. The only way to prevent damage occurring is to exclude construction from around significant trees to be retained. For further details of how the process of assessing trees for development purposes should occur please see Figure 1 of BS 5837: 2005 - which highlights how trees and their assessment fits into the development process.

Tree Survey
In basic terms, for the purposes of the council, if there are significant numbers of trees, large trees or TPO'd/CA trees on or adjacent the development site a tree survey will be required. Principally, this survey should contain the following information:

  • Health
  • Vigour
  • Condition
  • Species
  • Height
  • Trunk diameter at 1.5 AGL
  • Category
  • Age
  • Relevant details/significant defects
  • Remedial works required

Illustrate:

  • Colour coded accurate existing true crown spreads
  • Tree protection zone (including BRE requirements where applicable)
  • Professionally assessed mature crown spread (where significant growth still expected)

This report will generate the information required to complete an Arboricultural Implication Assessment and Tree Constraints Plan (TCP)

Tree Constraints Plan and Arboricultural Implication Assessment:
The tree constraints plan will take into account the influence that trees will have on the proposed layout. The tree constraints plan will show all above and below ground constraints (information regarding this is available in BS5837:2005)

Certain trees are of such importance and sensitivity that they may prevent the development occurring or modify the design/layout. Care must be taken to avoid misplaced tree retention. An attempt to retain too many or inappropriate trees on a site will cause an excessive pressure on the trees during the development process and may subsequently require their removal. The end result of trying to retain inappropriate trees may actually cause the development to lose more trees than was necessary if suitable retentions were provided to begin with.

During the design stage the following factors need to be taken into account:

  • TPO/CA
  • The effect that the proposed development will have on the amenity value of the trees both on and near the site.
  • Above and below ground constraints
  • Construction of the proposed development
  • Can the design layout be changed to accommodate the retention of trees that would be at risk or lost.
  • Infrastructure requirements including such aspects as substations, refuse stores, lighting, signage and CCTV requirements.
  • End use of space
  • Can tree loss due to development be mitigated acceptably by new tree planting.

Of particular importance are old trees that will become enclosed within a development. Such trees are often less resilient to change and are likely to die before the proposed buildings become obsolete. In these instances the retention of large old trees should be limited to large open spaces and large gardens such that any future removals are easily undertaken. Realistic assessment of the likely impacts on the final development must be made. This is to say the completed building in 10 years time. The proposal must take into account the full characteristics of the tree and allow space for it's growth and future development. Relationships between windows and trees are important where light may be an issue. Obviously orientation and aspect are important as is the growth habit and leaf type. Both trees and structures can be damaged by constant whipping of branches against roof/walls. Future growth of large branches may also create direct damage to buildings. Leaves and fruit of some species can cause problems with damage to vehicles, footpaths, blocking gullies etc. Also to consider are those tree species that produce large amounts of pollen i.e. Cedar. The tree constraint plan and arboricultural implication assessment then advise which trees are desirable to retain and how the proposed development will affect them.

Arboricultural Method Statement:
Some development works may occur within the root protection areas that, if done in certain ways will not be detrimental to the health of the trees to be retained. In these instances an Arboricultural Method Statement will be required such that the impact on the tree will be limited or non-existent, this is usually for items such as digging for foundations, demolition works prior to construction or 'no-dig' driveways.

Implementation and Monitoring:
Sites containing a large number of, or extremely important trees will require a schedule of implementation and monitoring with regard to trees to be retained. This ensures that a qualified professional arboriculturist will monitor the site at regular intervals to ensure that the fencing is being maintained correctly. Monitoring or site supervision will also be required if works are being undertaken within RPAs or CEZs in order that there are no detrimental affects to the retained trees. The implementation and monitoring report will be provided to both the developer and the local authority and is a rolling record of the tree protection etc on the site.