In any planning or development of a site, the local environment must be protected. An Arboricultural Impact Assessment (AIA) is needed for a planning application covering the impact on trees from construction to after the development is complete.

There are two key impact areas to cover, which are:

  1. Below ground impact risks (including roots and soil),
  2. Above ground impact risks (including the tree trunk, canopy, branches and bark).
  3. Future property impact risks (potential issues after development has completed).

The arboricultural impact assessment report on the site will categorise trees in accordance with BS5837 Trees in relation to design, demolition and construction.

Consequently, the uses of the AIA report will ultimately produce a conclusion for an Arboricultural Method Statement

What’s included in an Arboricultural Impact Assessment?

An arboricultural impact assessment will form part of an arboricultural report from a qualified Arboriculturalist tree surveyor. They will attend the site with surveying equipment. This AIA is accompanied by the following information.

Tree Survey

A tree survey provides detailed information about the trees within the site of private or public planned development. This first stage will include above-ground impact risks of the trees specifications and their:

  • species,
  • height
  • diameter of the trunk,
  • crown spread,
  • clearance from the ground to the lower canopy,
  • stage of life,
  • overall health in regards to disease and damage.

Furthermore, an Arboriculturalist will tag these trees for future observations and updating records.

Tree Constraints Plan

In most cases, an arboricultural tree survey will use highly specialised equipment to help draw a Tree Constraints Plan (TCP). This is the method of creating a precise and clear plan onto a topographical site survey.

This TCP contains the GPS positions, dimensions and spread of all trees in the area, plotted at the time of the tree report. Consequently, this will be used to make an informed decision on management of the trees, tree protection and preservation.

Tree Impact Plan

In this part of the report, all trees that will be impacted by future development will be listed, with help from the Tree Constraints Plan. This will also highly any areas where construction or groundworks could impact any below-ground risks. The tree impact plan will cover:

  • Trees suitable for retention
  • Trees to be removed
  • Trees to be pruned
  • Tree loss evaluation
  • Tree protection
  • Shading
  • Direct Damage
  • Root Protection Areas

Conclusion of the Arboricultural Method Statement

Finally, an Arboricultural Method Statement will detail how to manage the impact of construction and development on the trees. In the tree surgeon industry, it’s basically a plan of action to avoid damage to the crown or roots of the protected trees.

Furthermore, local authorities expect all Arboricultural Method Statements to be completed in accordance with BS5837. All identified tree work will also need to be carried out to BS3998.

The statement will indicate exactly when and how construction or groundwork in the area will be completed. To protect trees this will usually detail the:

  • banning of the use of diggers in tree protection zones,
  • installation of protective fencing,
  • use of above-ground boarding to avoid soil compacting,
  • routes of heavy machinery through a site,
  • locations of chemical storage and fires,
  • landscaping methods after construction.

It’s extremely important the Arboricultural Method Statement addresses all data collected in the tree survey, tree constraints plan and Arboricultural Impact Assessment  – to avoid a future development plan being rejected by its local authority.

Using the Arboricultural Impact Assessment for future landscaping

In fact, most of the Arboricultural tree survey can be used after construction has been completed for tree management purposes.

The trees, both old and new, will require monitoring to ensure there is no risk to the public or property. The data will help identify the need for a crown reduction, crown raising or tree pollarding.

In the long term, it is always best to contract an arborist for future tree management and tree care. By monitoring and keeping the tree survey up to date it, the risks to protected trees, public and property are kept highly manageable.

Arboricultural Impact Assessment screenshot

Tree Constraints Plan in Norwich