What is a Tree Risk Assessment?
A tree risk assessment (TRA) is a professional evaluation of a tree by a certified arborist to determine the potential risk of it failing (falling or breaking) and causing damage or injury. The goal is to proactively identify and mitigate these risks to ensure the safety of people and property while promoting the tree's health and longevity.
Why is a tree risk assessment important?
1. Public Safety: Identifying and mitigating hazardous trees reduces the risk of injury or property damage from fallen limbs or trees.
2. Property Protection: Proactive assessments can prevent costly damage to homes, vehicles, and other structures.
3. Legal Compliance and Liability Reduction: Property owners may have a legal responsibility to ensure their trees are safe, and documented assessments can demonstrate due diligence, potentially reducing liability in case of an accident.
4. Tree Health and Longevity: Early detection of diseases, infestations, and structural issues allows for timely intervention to improve tree health and extend their lifespan.
5. Urban Planning and Development: Tree risk assessments can inform decisions about retaining trees during construction projects and help in sustainable urban forestry.
How is a tree risk assessment performed?
1. Visual Inspection: The arborist thoroughly examines the tree's overall health, crown structure, trunk, branches, and root system for signs of decay, disease, or structural defects. They look for visible issues such as leaning, cracks, dead or broken branches, abnormal bark, and fungal growth. (Level 1, Level 2)
2. Health and Structural Evaluation: The assessment delves deeper into the tree's health and structural integrity, identifying signs of disease, pest infestations, weak branch attachments, and root damage. (Level 1, Level 2)
3. Site Conditions: The surrounding environment is also evaluated, considering factors like soil composition, drainage, proximity to structures (buildings, power lines, roads), and pedestrian traffic. (Level 1, Level 2, Level 3)
4. Advanced Diagnostics (if needed): For a more detailed analysis, arborists may use specialized tools like resistance drilling to detect internal decay, sonic tomography to assess structural integrity, or aerial drones for examining the upper portions of tall trees. (Level 3)
5. Risk Rating: Based on the assessment findings, the arborist assigns a risk rating, often categorized as low, moderate, high, or extreme. This rating is often calculated using a formula: Risk = Probability x Consequences. (Level 2)
6. Recommendations and Mitigation Strategies: The arborist then provides a report detailing their findings and recommends appropriate actions to manage the identified risks. These may include pruning, cabling or bracing, disease treatment, or in cases of severe risk, tree removal. (Level 1, Level 2, Level 3)
Who needs a tree risk assessment?
Homeowners: To ensure the safety of their families, homes, and property, especially with large or aging trees, or after severe weather. Regular assessments can also help maintain property aesthetics and value.
Property Owners with Trees Along Sidewalks or Public Rights-of-Way: In many jurisdictions, property owners are responsible for maintaining trees that front public areas to prevent interference with public use and ensure safety.
Commercial Property Managers: To safeguard employees, customers, and visitors, protect buildings and infrastructure from potential tree failures, and reduce liability risks. Commercial properties often have high-traffic areas where tree hazards can be particularly dangerous.
Municipalities and Urban Foresters: They manage trees in public spaces like parks, street rights-of-way, and other community areas. Tree risk assessments help ensure public safety, comply with regulations, and make informed decisions about managing the urban forest.
Anyone with Concerns About Tree Health or Stability: Even if a tree appears healthy, it's wise to consult a certified arborist. They have studied hard to become certified, which means they know more than the average tree service and homeowner. A tree can look healthy on the outside but still be a high risk with unknown defects, that only a certified arborist can detect with knowledge and specialized tools. On the other hand, a tree can have a huge defect that can seem like a reason to remove a tree, when in reality there is enough response wood to keep your tree standing for decades while still enjoying all the benefits.
Land Developers and Construction Professionals: Before and during development projects near existing trees, assessments can identify potential conflicts and help implement measures to protect trees and avoid structural damage.
