Risk assessment involves the identification and evaluation of trees for the likelihood of failure and the severity of consequences. Tree owners and managers seek out this service to satisfy their basic legal duty of care with professional guidance. NOTE: Jerry held an active Tree Risk Assessment Qualification from 2012-2023 and has multiple publications on the topic, but no longer conducts formal assessments.
Limited visual
The simplest method of tree risk assessment involves a cursory visual inspection, often from a vehicle. It has some distinct advantages:
- It is fast
- It fits easily within most budgets
- It can efficiently identify high-risk trees needing detailed investigation
At the same time, its quality is low:
- Its perspective is limited, as commonly only one side is observed
- It can only pick up the most obvious features
- It is unable to see much of the crown
We usually only carry out this level of risk assessment during an inventory where risk assessment has not been included in the scope of work.
Basic
The bulk of tree risk assessment consists of a detailed examination of the tree and site. Only basic tools are used at this level such as a mallet, binoculars and a shovel. It is a responsible form of risk assessment:
- It supplies a thorough investigation of the tree
- It can detect many subtle but serious defects
- It evaluates important factors such as load, target and health
At the same time, the basic level has its own limitations:
- It produces little information about underground tree parts
- Defects in the upper crown can be difficult to evaluate
- It relies primarily on signs and symptoms
We offer our clients the extensive training, research and experience required for reliable assessments and recommendations.
Advanced
When significant trees or targets are in question, basic tree risk assessment can result in the recommendation that advanced techniques be applied. Some of the more common advanced techniques we employ are these:
- Aerial inspection, often using a bucket truck
- Measurement of the extent of decay
- Root crown excavation with an air tool
These and other advanced techniques–load testing, for instance–produce a more detailed and objective picture of the tree, and we recommend one or more in difficult and important cases. Some of them are quite expensive, however, and none of them removes the necessity for human interpretation of the results and judgment about the recommendation.
