Tree Risk Assessment

Managing trees involves managing tree risk: failure of a tree or its parts is often predictable.

Consultants at Tree Dimensions have a Tree Risk Assessment Qualification (TRAQ) gained from the International Society of Arboriculture (ISA).

The TRAQ methodology is a systematic and qualitative process to identify, analyse and evaluate tree risk, which is consistent with
AS/NZS ISO 31000:2009 Risk management – Principles and guidelines.


Some tree defects are readily discernible from a ground–level inspection.

Some tree defects are visible from an aerial inspection only.

Tree Risk can be evaluated at three levels:

Level 1

A Level 1 inspection is a limited walk-by or drive-by inspection to rapidly identify trees with structural defects likely to lead to an imminent or probable likelihood of failure.

Level 1 inspection: walk-by and drive-by assessments.

Level 2

A Level 2 inspection is the most common assessment that requires detailed visual inspection of the subject tree and its surrounding area. A Level 2 inspection may require the use of simple tools such as binoculars, a probe or a sounding mallet.

Level 2 inspection: testing stem soundness.

Level 2 inspection: assessing crown health.

Level 3

A Level 3, or advanced, inspection provides detailed information on specific defects, tree parts, targets or site conditions. Specialised equipment, such as an Arbotom, or an aerial inspection may provide the additional information required to determine whether to retain or remove a tree.

Level 3 inspection: an aerial assessment, whether using a drone or climbing, provides clients with critical information required for successful tree management.

Level 3 inspection: a non–destructive investigation of tree roots.

Level 3 inspection: sonic tomography provides information on internal stem structure.


Tree Dimensions has highly trained assessors of tree health and structure, tree risk to its surrounds, and of the probable consequences should a tree or tree part fail structurally. The consulting team is experienced with: