Basic Tree Risk Assessment Form - International Society of Arboriculture (Isa)

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Basic Tree Risk Assessment Form
Client _______________________________________________________________ Date ___________________ Time _________________
Address/ Tree location _________________________________________________________ Tree no. ____________ Sheet _____ of _____
Tree species _________________________________________ dbh_____________ Height ___________ Crown spread dia. ____________
Assessor(s) __________________________________________ Time frame_____________ Tools used______________________________
Target Assessment
Target zone
Occupancy
rate
1– rare
Target description
2 – occasional
3 – frequent
4 – constant
1
2
3
4
Site Factors
History of failures _____________________________________________________________ Topography Flat Slope _________% Aspect _____
Site changes None  Grade change  Site clearing Changed soil hydrology Root cuts Describe _____________________________________
Soil conditions Limited volume Saturated  Shallow Compacted Pavement over roots ______% Describe __________________________
Prevailing wind direction ______ Common weather Strong winds  Ice Snow Heavy rain  Describe ______________________________
Tree Health and Species Profile
Vigor Low  Normal  High 
Foliage None (seasonal)
None (dead) Normal _____ %
Chlorotic _____%
Necrotic _____%
Pests_____________________________________________________ Abiotic ________________________________________________________
Species failure profile Branches  Trunk Roots Describe ____________________________________________________________________
Load Factors
Wind exposure Protected Partial  Full  Wind funneling  ________________________ Relative crown size Small  Medium Large
Crown density Sparse Normal Dense
Interior branches Few Normal Dense Vines/Mistletoe/Moss  _____________________
Recent or planned change in load factors _________________________________________________________________________________________
Tree Defects and Conditions Affecting the Likelihood of Failure
— Crown and Branches —
Unbalanced crown  LCR ______%
Cracks  ___________________________________ Lightning damage 
Dead twigs/branches  ____% overall Max. dia. ______
Codominant  __________________________________ Included bark 
Broken/Hangers Number __________
Max. dia. ______
Weak attachments  ___________________ Cavity/Nest hole ____% circ.
Over-extended branches 
Previous branch failures  _______________
Similar branches present 
Pruning history
Dead/Missing bark 
Cankers/Galls/Burls 
Sapwood damage/decay 
Crown cleaned 
Thinned 
Raised
Conks  Heartwood decay  ________________________
Reduced
Topped 
Lion-tailed 
Flush cuts
Other
Response growth
Main concern(s)
Load on defect
N/A 
Minor  Moderate  Significant 
Likelihood of failure
Improbable
Possible
Probable
Imminent
— Trunk —
— Roots and Root Collar —
Dead/Missing bark 
Abnormal bark texture/color 
Collar buried/Not visible  Depth________
Stem girdling 
Codominant stems 
Included bark 
Cracks 
Dead 
Decay  Conks/Mushrooms 
Sapwood damage/decay  Cankers/Galls/Burls  Sap ooze 
Ooze 
Cavity  _____% circ.
Lightning damage  Heartwood decay  Conks/Mushrooms 
Cracks 
Cut/Damaged roots  Distance from trunk _______
Cavity/Nest hole _____ % circ. Depth _______
Poor taper 
Root plate lifting 
Soil weakness 
Lean _____ ° Corrected? ________________________________
Response growth
Response growth
Main concern(s)
Main concern(s)
Load on defect
N/A  Minor  Moderate  Significant 
Load on defect
N/A  Minor  Moderate  Significant 
Likelihood of failure
Likelihood of failure
Improbable
Possible
Probable
Imminent
Improbable
Possible
Probable
Imminent
Page 1 of 2
Basic Tree Risk Assessment Form
Client _______________________________________________________________ Date ___________________ Time _________________
Address/ Tree location _________________________________________________________ Tree no. ____________ Sheet _____ of _____
Tree species _________________________________________ dbh_____________ Height ___________ Crown spread dia. ____________
Assessor(s) __________________________________________ Time frame_____________ Tools used______________________________
Target Assessment
Target zone
Occupancy
rate
1– rare
Target description
2 – occasional
3 – frequent
4 – constant
1
2
3
4
Site Factors
History of failures _____________________________________________________________ Topography Flat Slope _________% Aspect _____
Site changes None  Grade change  Site clearing Changed soil hydrology Root cuts Describe _____________________________________
Soil conditions Limited volume Saturated  Shallow Compacted Pavement over roots ______% Describe __________________________
Prevailing wind direction ______ Common weather Strong winds  Ice Snow Heavy rain  Describe ______________________________
Tree Health and Species Profile
Vigor Low  Normal  High 
Foliage None (seasonal)
None (dead) Normal _____ %
Chlorotic _____%
Necrotic _____%
Pests_____________________________________________________ Abiotic ________________________________________________________
Species failure profile Branches  Trunk Roots Describe ____________________________________________________________________
Load Factors
Wind exposure Protected Partial  Full  Wind funneling  ________________________ Relative crown size Small  Medium Large
Crown density Sparse Normal Dense
Interior branches Few Normal Dense Vines/Mistletoe/Moss  _____________________
Recent or planned change in load factors _________________________________________________________________________________________
Tree Defects and Conditions Affecting the Likelihood of Failure
— Crown and Branches —
Unbalanced crown  LCR ______%
Cracks  ___________________________________ Lightning damage 
Dead twigs/branches  ____% overall Max. dia. ______
Codominant  __________________________________ Included bark 
Broken/Hangers Number __________
Max. dia. ______
Weak attachments  ___________________ Cavity/Nest hole ____% circ.
Over-extended branches 
Previous branch failures  _______________
Similar branches present 
Pruning history
Dead/Missing bark 
Cankers/Galls/Burls 
Sapwood damage/decay 
Crown cleaned 
Thinned 
Raised
Conks  Heartwood decay  ________________________
Reduced
Topped 
Lion-tailed 
Flush cuts
Other
Response growth
Main concern(s)
Load on defect
N/A 
Minor  Moderate  Significant 
Likelihood of failure
Improbable
Possible
Probable
Imminent
— Trunk —
— Roots and Root Collar —
Dead/Missing bark 
Abnormal bark texture/color 
Collar buried/Not visible  Depth________
Stem girdling 
Codominant stems 
Included bark 
Cracks 
Dead 
Decay  Conks/Mushrooms 
Sapwood damage/decay  Cankers/Galls/Burls  Sap ooze 
Ooze 
Cavity  _____% circ.
Lightning damage  Heartwood decay  Conks/Mushrooms 
Cracks 
Cut/Damaged roots  Distance from trunk _______
Cavity/Nest hole _____ % circ. Depth _______
Poor taper 
Root plate lifting 
Soil weakness 
Lean _____ ° Corrected? ________________________________
Response growth
Response growth
Main concern(s)
Main concern(s)
Load on defect
N/A  Minor  Moderate  Significant 
Load on defect
N/A  Minor  Moderate  Significant 
Likelihood of failure
Likelihood of failure
Improbable
Possible
Probable
Imminent
Improbable
Possible
Probable
Imminent
Page 1 of 2
Risk Categorization
Likelihood
Consequences
Failure & Impact
Failure
Impact
(from Matrix 1)
Risk
rating
of part
Conditions
Target
(from
of concern
protection
Tree part
Matrix 2)
1
2
3
4
Matrix 1.
Likelihood matrix.
Likelihood of Impacting Target
Likelihood
of Failure
Very low
Low
Medium
High
Imminent
Unlikely Somewhat likely
Likely
Very likely
Probable
Unlikely
Unlikely
Somewhat likely
Likely
Possible
Unlikely
Unlikely
Unlikely
Somewhat likely
Improbable Unlikely
Unlikely
Unlikely
Unlikely
Matrix 2.
Risk rating matrix.
Consequences of Failure
Likelihood of
Failure & Impact
Negligible
Minor
Significant
Severe
Very likely
Low
Moderate
High
Extreme
Likely
Low
Moderate
High
High
North
Somewhat likely
Low
Low
Moderate
Moderate
Unlikely
Low
Low
Low
Low
Notes, explanations, descriptions
_____________________________________________________________________
________
Mitigation options
Residual risk
____________________________________________________________________________________
________
Residual risk
____________________________________________________________________________________
________
Residual risk
____________________________________________________________________________________
________
Residual risk
Overall tree risk rating
Work priority
Low
Moderate
High
Extreme
1
2
3
4
Overall residual risk
Recommended inspection interval __________________
Low
Moderate
High
Extreme
Data Final  Preliminary Advanced assessment needed No Yes-Type/Reason ________________________________________________
Inspection limitations None Visibility Access Vines Root collar buried Describe ___________________________________________
This datasheet was produced by the International Society of Arboriculture (ISA) and is intended for use by Tree Risk Assessment Qualified (TRAQ) arborists – 2013
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Download Basic Tree Risk Assessment Form - International Society of Arboriculture (Isa)

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