Arborist Risk Assessment


Tree owners and managers have a duty of care to ensure that trees are managed so that they have an acceptable level of risk associated with them. This is especially important in public areas, schools and other high use locations.

Arborists Approach to Calculating Risk from Trees

Assessing risk from trees is always difficult, yet we as professional arborists have a responsibility to do this to the best of our individual expertise. Peter Gray has trained extensively in tree risk assessment with both QTRA’s Quantified Tree Risk Assessment and VALID Tree Risk-Benefit Management.

Can an Arborist Tell when a Tree will Fail?

Predicting tree failure is very uncertain, so instead  we seek to manage the risk from tree failure by determining whether or not the risk is acceptable. This risk is calculated as a probability with QTRA and by using an App with VALID.  The outputs are given as being an Acceptable risk, Tolerable (if as Low as Reasonably Practicable) or Unacceptable.

These risk ranges can then be used by the tree manager to assist in deciding what if any measures should be taken to reduce the risk.  It is important to remember that overall, the risk from trees is extremely low and that trees provide us with many benefits.