Tree Risk Assessment
Most tree risk assessments don't start with a question about the tree — they start with the surrounding site and potential targets. Does this tree actually need to come out, or does it just look intimidating? Tree risk assessment is how you get a defensible answer instead of a guess.
What "Risk" Actually Means
Risk is three separate factors multiplied together: how likely a failure is, how likely that failure is to hit a target (a person, a house, a car), and how bad the consequences would be if it did. The formula I use, straight from ISA's Best Management Practices, is Likelihood of Failure × Likelihood of Impact × Consequences of Failure = Risk. The job of an assessment is to work through that math methodically instead of going with however alarming the tree looks at first glance.
Three Levels of Tree Risk Assessment
Limited Visual (Level 1)
A one-sided visual assessment from a defined vantage point — a sidewalk, a parking lot, a property line. It's the right tool for screening a lot of trees quickly, or for situations where you can't access the full site. It catches the obvious stuff: dead trees, major broken limbs, visible cavities. It won't catch much beyond that, and it's not meant to.
Basic (Level 2)
A full 360-degree, ground-based visual inspection of the crown, trunk, trunk flare (the base where trunk meets root system), and visible roots, along with the site conditions and targets around the tree. This is the level that fits most situations — a concerned homeowner, an HOA board, an insurance claim, an attorney who needs an opinion backed by industry consensus methodology. I may use a mallet to sound the trunk for decay or a probe to check cavities.
Advanced (Level 3)
Where Level 2 isn't enough — usually because there's a defect that needs more than a visual assessment. The Advanced (Level 3) assessment brings in tools like resistance drilling or sonic tomography to see what's happening inside the trunk. It costs more and takes longer.
What the Process Looks Like
I visit the site and inspect the tree, documenting species, condition, defects, and targets within the target zone. I take my notes and data back to the office for analysis and report preparation. Within a couple of weeks you’ll have your photodocumentary tree risk assessment report detailing methodology, observations, findings, and mitigation options.
Your Options After an Assessment
A risk rating isn't a verdict, it's information that helps you make an informed decision. After a Limited Visual or Basic assessment, there are five typical paths forward:
Monitor
Advanced assessment
Remove targets
Treat the tree
Remove the tree
Which one makes sense for you may depend on the risk rating, the cost and likely success of treatment, and how much risk you're willing to live with. The decision is always yours.
Appropriate for: HOAs, property managers, attorneys, homeowners with a specific concern, institutional properties.
Not sure if your situation calls for a Level 1, Level 2, or something else entirely?Get in touch and we'll figure out the right scope together.
How to Get Started
Every engagement begins with a proposal. Reach out with a brief description of your situation — what you're dealing with, what you need, and when — and I'll follow up promptly to discuss scope and fees.
JP McDonnell | jp@shakeragconsulting.com