Is my tree hazardous? 

The International Society of Arboriculture has developed science-based objective protocols for determining levels of risk posed by trees within striking distance of human-use areas.

An ISA TRAQ (Tree Risk Assessment Qualification) Level I assessment usually begins with a visual assessment of a population of trees near potential targets conducted from a defined perspective to identify obvious defects or conditions of concern. This limited visual assessment typically focuses on identifying trees with imminent and/or probable likelihood of failure.

TRAQ Level I evaluations are the fastest, but least thorough means of risk assessment and are intended primarily for managing large populations of trees when time and resources are limited. We offer these assessments to provide tree managers with an adequate level of information to accomplish their risk management goals for large areas with multiple potential targets.

Methodology

• Identify the location and/or selection criteria of trees to be assessed.

• Determine the most efficient route for assessing large populations of trees and documenting the route taken.

• Assess the tree(s) of concern from the defined perspective (walk-by or drive-by).

• Record locations of trees that meet the defined criteria (for example, significant defects or other conditions of concern, trees that require mitigation, or trees that require a higher level of assessment).

• Evaluate the risk based on observations and assumptions (a risk rating is optional).

• Submit a report indicating risk level(s) and mitigation options and/or recommendations.

An ISA TRAQ Level II Basic Risk Assessment is an objective protocol to categorize the risk posed to targets within striking distance in the event of a whole tree or large limb failure and provide appropriate recommendations to maintain risk at acceptable levels. This assessment assumes a specified timeframe based on observations made at the time of the site visit. 

The Tree Assessment procedure involves the examination of the following factors:

·       The crown of the tree is examined for vigor. This is comprised of inspecting the foliage, buds and branches for color, density, form, annual shoot growth, limb dieback, or disease. 

·       The bole or main stem of the tree is inspected for decay signs of which may include cavities, wounds, fungal fruiting bodies (conks or mushrooms), seams, insects, bleeding, callus development, broken or dead tops, structural defects, or unnatural leans. 

·       The root collar and roots are inspected for the presence of decay, insects, and/or damage, as well as if they have been injured, undermined or exposed, or if the original grade has been altered.  

The inspection method may include examining the tree with binoculars or sounding the trunk with a mallet.  No invasive methods are utilized.  

The Target Assessment procedure involves the examination of the following factors:

·       The ‘Target Zone’ is determined by considering the height of the tree, crown spread, likely direction of fall, slope, and potential for shattering and ejecting debris a distance of up to 1.5x the height of the tree.

·       Determine the ‘Occupancy Rate’, or the amount of time one or more targets are within the target zone.

·       Potential targets are identified as ‘Static’ such as a house or other permanent structure, ‘Movable’ such as a parked car or picnic table, or ‘Mobile’ such as a pedestrian or bicyclist. 

These observations are recorded in the field on an ISA Basic Tree Risk Assessment Form and used to inform the Risk Categorization Chart. This chart organizes the Likelihood of Failure, Likelihood of Impact, and Consequences of Failure into a matrix that determines the ‘Overall Tree Risk Rating’.