CTSP Hazard and Risk Assessment 3 — Questions and Answers
Question 1: In the ISA Tree Risk Assessment Qualification (TRAQ) framework, which three factors combine to determine overall tree risk?
- Species, age, and crown density
- Likelihood of failure, likelihood of impact, and consequences (Correct answer)
- Root depth, stem taper, and canopy spread
- Decay presence, lean angle, and wind speed
Correct answer: Likelihood of failure, likelihood of impact, and consequences
TRAQ defines overall risk as the product of likelihood of failure, likelihood of impact on a target, and the consequences of that impact.
Question 2: Which condition would most likely place a tree into the 'Poor' structural condition rating?
- Minor deadwood less than 2 inches in diameter
- Large open cavity occupying more than 30% of the trunk cross-section (Correct answer)
- A single codominant stem with no included bark
- Slightly uneven crown distribution
Correct answer: Large open cavity occupying more than 30% of the trunk cross-section
A large open cavity removing more than 30% of the trunk's cross-sectional area severely compromises structural integrity.
Question 3: What is the primary purpose of establishing a tree risk tolerance threshold for a site?
- To set a minimum height for tree removal
- To define the highest risk level acceptable before mitigation is required (Correct answer)
- To calculate the appraised value of hazard trees
- To determine the pruning cycle for the property
Correct answer: To define the highest risk level acceptable before mitigation is required
A risk tolerance threshold defines the maximum acceptable risk level, triggering mitigation actions when that level is exceeded.
Question 4: A street tree with a significant lean over a sidewalk also shows root plate lifting on the tension side. What does root plate lifting indicate?
- Healthy lateral root development
- Active windthrow failure in progress or high failure potential (Correct answer)
- Normal growth response to soil compaction
- Successful cable-bracing installation
Correct answer: Active windthrow failure in progress or high failure potential
Root plate lifting signals that the tree's root system is losing anchorage and the tree may be in the early stages of windthrow failure.
Question 5: Which of the following best describes a 'residual risk' after mitigation measures have been applied?
- The original risk rating before any work was done
- The remaining risk that still exists after mitigation actions are completed (Correct answer)
- The financial cost of removing a hazard tree
- The risk posed only by secondary targets near the tree
Correct answer: The remaining risk that still exists after mitigation actions are completed
Residual risk is the level of risk that remains after mitigation measures such as pruning, cabling, or removal have been implemented.
Question 6: An oak tree shows conks of Ganoderma species at the base. How does this finding affect risk assessment?
- It is cosmetic and does not affect structural integrity
- It indicates significant root and butt rot, elevating failure likelihood (Correct answer)
- It suggests a nutrient deficiency requiring fertilization
- It only affects the outer bark and is of minor concern
Correct answer: It indicates significant root and butt rot, elevating failure likelihood
Ganoderma species cause white rot of roots and the butt, substantially weakening the tree's foundation and increasing failure likelihood.
Question 7: When quantifying consequences in tree risk assessment, which target classification carries the highest weight?
- Occasionally occupied open lawn
- Infrequently used forest trail
- Permanently occupied residence or frequent-use area (Correct answer)
- Unoccupied storage shed
Correct answer: Permanently occupied residence or frequent-use area
Permanently occupied or frequently used structures and areas carry the highest consequence weight due to constant human presence.
CTSP Hazard and Risk Assessment 3
In the ISA Tree Risk Assessment Qualification (TRAQ) framework, which three factors combine to determine overall tree risk?