What is a Tree Risk Assessment?
A tree risk assessment is a detailed analysis of the potential risks to people and property associated with trees. The tree risk assessment NSW process is designed to identify diseases, pests and other structural issues that increase the likelihood of tree failure.
These arborist reports are especially important in high-use areas such as schools, public spaces and commercial sites, where tree failure poses a significant safety risk.
Councils, schools and property owners rely on tree hazard assessments to meet duty of care obligations and maintain a safe environment. Failure to manage the risks appropriately can result in liability, including fines or legal action in the event of damage or injury.
Methodologies used:
QTRA tree risk assessment
A quantified tree risk assessment compares the probability of harm from tree failure with the benefits of trees. The QTRA tree risk assessment consists of three different components:
- Target Evaluation: the likelihood of a target (people/property) being present
- Impact Potential: the size of the part of the tree likely to fall
- Probability of Failure: the likelihood that the tree or branch will fall
VALID tree assessment
The VALID tree assessment method combines qualitative and quantitative means to assess risk. It uses a specialised app to calculate risk levels, allowing for both simplified and detailed assessments depending on site requirements.
VTA tree assessment
A visual tree assessment is just that: a visual inspection to identify signs that a tree is under stress and likely to cause damage. This inspection considers pests, decay and cracks, and involves probing to detect internal defects.
Who needs a tree risk assessment?
Tree risk assessments for schools and tree risk assessments for commercial property sites are used to support duty of care obligations. These reports, also referred to as tree hazard assessments, are required for any site where trees have the potential to impact people, property or infrastructure.
They’re most commonly requested by:
- Schools, to ensure staff and student safety in high-use areas like ovals and playgrounds
- Councils, to manage tree populations within public spaces
- Commercial property owners and managers, where trees are located near buildings walkways and car parks.
It’s recommended that schools, councils and commercial property owners request annual tree risk assessments as part of their tree management strategies. Residential properties may also require assessments when trees pose a potential hazard.
What does the report include?
The tree risk report arborist document provides an analysis of every tree on the site and its associated risk level.
They usually include:
- Tree identification
- Assessment of overall tree condition
- Identification of defects
- Evaluation of potential targets
- Likelihood of failure
- A risk rating
- Recommendations, such as pruning, monitoring or removal
- Supporting photographic evidence
Liability and duty of care context
Schools, councils and commercial property managers have a responsibility to undertake a duty of care tree assessment to prevent potential harm.
In the event of damage or injury, a documented tree risk assessment report demonstrates that precautions were taken to manage risks. This can be critical in determining liability and distinguishing between natural events and negligence.
