What is tree risk assessment?
Tree risk assessment is a systematic process in which an arborist evaluates a tree's structural condition and likelihood of failure to determine potential risk to people or property.
An arborist performing tree risk assessment examines a tree's physical structure, health, and environmental context to calculate two key factors: the probability the tree will fail and the severity of impact if it does. This evaluation follows the Tree Risk Assessment Qualification (TRAQ) standard developed by the International Society of Arboriculture (ISA), which provides a consistent framework for identifying hazardous trees across different species, sizes, and conditions.
The assessment process typically involves on-site inspection of the trunk, branches, root system, and surrounding landscape. The arborist looks for signs of disease, decay, structural defects, improper pruning, and environmental stress. They evaluate what targets are at risk (homes, vehicles, pedestrians, utilities) and how likely the tree is to strike them if failure occurs. The result is a risk rating that helps property owners and municipal managers in Westchester County decide whether a tree should be monitored, pruned, removed, or left as-is.
Professional tree risk assessment matters because it prevents costly property damage and injuries. A tree that appears healthy may have internal decay or root compromise. Conversely, a tree with visible defects may pose minimal actual risk. Rather than guess, property owners and municipalities rely on certified arborists to apply TRAQ methodology and provide defensible, science-based recommendations.