Arboricultural Impact Assessment

Arboricultural Impact Assessments for planning applications and development projects near trees across Hampshire, Surrey, Sussex, Kent and London.

An Arboricultural Impact Assessment, often shortened to AIA, considers how a proposed development may affect existing trees on or near a site. It is usually prepared as part of a BS5837 report package, following an initial BS5837 tree survey and Tree Constraints Plan.

The assessment helps identify whether trees can be retained, whether any trees need to be removed, and how potential impacts can be avoided, reduced, or mitigated as part of the design and construction process.

What is an Arboricultural Impact Assessment?

An Arboricultural Impact Assessment is a report that evaluates the likely effects of a proposed layout on trees.

It considers the relationship between the proposed development and the existing tree constraints, including Root Protection Areas, canopy spreads, tree retention categories, proposed access, level changes, demolition, construction space, hard surfacing, services, and future use of the site.

The purpose is to provide a clear assessment of the arboricultural implications of the proposal, so that the design team, client, and local planning authority can understand how trees have been considered.

When is an AIA needed?

An AIA is commonly required where a planning application involves development close to trees, particularly where those trees may influence the layout or could be affected by demolition, construction, access, or changes in ground levels.

It may also be relevant for other types of development where planning permission is not required, such as some permitted development works, if trees are close enough to be affected. This is especially important where trees are protected by a Tree Preservation Order, located within a Conservation Area, or otherwise form an important constraint to the site.

An Arboricultural Impact Assessment is not the first stage of the BS5837 process. A BS5837 tree survey and Tree Constraints Plan are required first, as these establish the baseline information needed to assess the effects of the proposal.

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What does an AIA assess?

The assessment may consider:

trees proposed for retention
trees proposed for removal
any pruning required to facilitate the development
impacts on Root Protection Areas
impacts on tree canopies and available working space
demolition or construction activity near retained trees
proposed hard surfacing, foundations, services, drainage, or level changes near trees
site access, storage, scaffolding, plant movement, and buildability
future relationship between retained trees and the completed development
mitigation measures required to reduce or manage arboricultural impacts

The level of detail depends on the site, the trees present, and the nature of the development.

Impact Assessment Plan

The written Arboricultural Impact Assessment is accompanied by an Impact Assessment Plan.

This plan shows the proposed development in relation to the surveyed trees and key tree constraints. It identifies trees to be retained, trees to be removed, and the relationship between the proposed layout and the various arboricultural constraints present on the site, including Root Protection Areas, canopy spreads, and other factors that may influence the design.

Where needed, the plan can also identify areas where sympathetic design solutions or construction approaches are proposed to help retain trees and accommodate development within the site’s arboricultural constraints.

Draft feedback before final issue

As part of the AIA process, Flow Tree Consultancy provides draft feedback before the final report is issued.

This allows tree-related issues, design conflicts, mitigation measures, and possible amendments to be discussed with the project team before the final submission documents are completed.

This is particularly useful where trees influence layout, access, levels, construction methods, or the extent of proposed tree removal.

How the AIA fits into the BS5837 process

An Arboricultural Impact Assessment will follow the initial BS5837 tree survey and Tree Constraints Plan.

The tree survey records the trees on and near the site, while the Tree Constraints Plan shows the key above-ground and below-ground constraints that may influence the design. Once a proposed layout is available, the AIA assesses the effect of that design on the trees.

Depending on the project, the AIA may then lead into further information such as an Arboricultural Method Statement and Tree Protection Plan.

For a more detailed explanation of this stage, read our article on what an Arboricultural Impact Assessment is.

You can find more information about the wider BS5837 planning and development services provided by Flow Tree Consultancy.

Professional arboricultural advice

Flow Tree Consultancy is led by a qualified arboricultural consultant with a First Class BSc (Hons) in Arboriculture and Urban Forestry, Professional Membership of the Arboricultural Association, LANTRA Professional Tree Inspection training, and a decade of industry experience.

This includes extensive experience providing arboricultural input for planning and development projects, including BS5837 surveys and reports, Arboricultural Impact Assessments, tree retention and removal advice, and mitigation strategies for development near trees.

You can find out more about Flow Tree Consultancy’s qualifications, experience and professional approach on the About page.