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What is Tree Risk and How do you Measure it?

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Tree Risk Assessment

Tree Risk is a measure of risk associated with a part or whole tree failing and hitting a target (person, building, power lines, etc).

There are several ways in which the level of risk can be represented and often is rated from Extreme to Low. There are also mathematical models such as QTRA (Quantified Tree Risk Assessment) that gives the risk rating as a fraction anything less than 1/10,000 is considered high risk and should be dealt with.


Tree risk assessment example

Identical Defective Trees in two Different Locations can have Different Risk Ratings Depending on Targets

As an example if we had two identical trees with major structural defect with a high likelihood of failure the risk rating would be as follows.

If the tree was located adjacent to a major thoroughfare it would have a high risk rating.

If the tree was located in Bush land where one person passes by per day would have a much lower risk rating.

tree risk assessment


Why Do You Need to be Aware of Tree Risk?

As a manager or owner of a site you have a duty of care to the staff, customer, visitors or any person on site for their safety.

Too often trees get forgotten when it comes to safety and it only becomes a problem when there is a tree failure.

Contrary to popular believe and the media trees are relatively predictable and in most instances tree failure can be predicted with a reasonable degree of accuracy.

When assessing Tree Risk it is based on normal weather patterns as excessive winds and storms can damage even healthy trees.

What you want to be aware of is the overall condition of your tree stock and the associated risk with defective trees. It gives you a baseline and helps you allocate appropriate budgets to managing your tree stock.

Planned preventative tree maintenance is always cheaper than unplanned reactive tree work that has not been allowed for in the budget and also reduces the long term cost of trees. management.


Tree Failure is Predictable!

Most tree failure could have been avoided if the trees had been assessed by a minimum AQF Level 5 Arborist.

They have the skills and knowledge to identify tree hazards and give guidance on the management of your trees.


Reduced Tree Maintenance Cost:

Research has shown that sites which have a tree management program are not only able to reduce their tree risk over time but are also able to reduce their tree maintenance related costs over time.

By reducing reactive unplanned and often costly tree work following an incident or storm, planned and properly allocated funding to the appropriate areas not only reduces risk but also reduces tree maintenance costs.


What you can do to Reduce Tree Risk and Stay Safe:

Just do something and don’t ignore the trees on your site. In the event of an incident ignorance will not help you.

At a minimum have an AQF Level 5 Arborist check your trees annually and document their findings. Then work to the document and address the most pressing issues first. Make sure you keep work records.

If your budget allows a Tree Management Program is the best option. It is a computerised tree management solution tailored to your site and budget. It keeps records of all inspections and tree works carried out. Data can be filtered to ensure that the highest risk trees are addressed first.

Remember you need to view your trees as assets and maintain them. Would people still visit your site if there were no trees? Look after them and everyone can enjoy them without the fear of getting hurt.

Don’t ignore your trees, they are an asset and in the event of an incident you want to be able to show that you manage and maintain your trees as part of your duty of care.

 stay safe and assess your tree risk today