A First

The need to be precise is one of legal principle. As a consultant you are brought in as an expert and thus a higher standard is applied to what you put forth when called upon to render an opinion.

I assisted Phil van Wassenenaur on an assessment of a 75' Red Oak That had partially grown over a stone wall. Without the very precise testing done it would've been considered a hazard tree by most arborists by visual inspection. The analysis of the data collected, using computer modelling indicated that it was stable. The recommendation was a 1 metre crown reduction. In this case the client was hoping to save the tree but was concerned as the tree was within 15' of the main house.

Language is very important, choose your words carefully because a sharp lawyer will seize on any ambiguity they perceive.
 
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I think the hazard issue really should be for the tree or its components breaking and causing damage. I would also add trip issues to this.

I think property damage (actually) caused by a tree is a seperate issue and category and should be addressed as such.

[/ QUOTE ]This is an example of the confusion that comes about when we talk about hazard instead of risk.

Are you proposing a separate process for assessing damage by roots, and another for branches? Or one for risk to people and another for risk to property? I don't know how this could be done--care to share a draft of this? Certainly risk from trunk or branch failure to humans has a much higher target rating than risk from roots to property such as house foundations.

I'm managing a white oak that cracked a basement wall 13 years ago but the damage has not grown in that time even though the tree has. Those owners tolerate the risk of further damage. Whether or not Telluride's definition of "hazard" does not include damage to property, maybe it should stay.

I think skew has documented some possible reasons for removing the cottonwood, but how easily can one judge a tree's rooting space? Roots may have grown under around through and outside of what seem like obstacles--how do you know? Even though his opinion was biased--"skewed" if you will (sorry)--, lacking independence and objectivity and slanted toward removal, it may still be valid. Or not.

My question is why the first guy recommended an aerial inspection, and the second guy didn't (was his mind made up before he got there?), and no one has done it. Of course we are all guessing wildly without pictures or being there.
 

Attachments

Sure there is a risk of damage from a hazard tree dropping dead limbs etc., and a risk of damage to things like sidewalks. I am not sure though that a root can be called a hazard because it is lifting a driveway or cracking a wall. I think it is a different problem and should be acknowledged as such. The example of a root clogging the sewer is a risk and causing damage but is likely not hazardous.
 
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Sure there is a risk of damage from a hazard tree dropping dead limbs etc., and a risk of damage to things like sidewalks. I am not sure though that a root can be called a hazard because it is lifting a driveway or cracking a wall. I think it is a different problem and should be acknowledged as such. The example of a root clogging the sewer is a risk and causing damage but is likely not hazardous.

[/ QUOTE ]This is an example of the confusion that comes about when we talk about hazard instead of risk.


How are you defining "hazard"?
 
You raise an interesting point that I don't think I can answer immediately. Need to think on it.

I feel hazard has a more immediate (time) component than risk. So all trees have a risk component, but the hazard may be high or low but should not be applied to events which may occur in the distant future.
 
Below is one definition, interesting that damage from root pressure is not a "hazard" by this definition because it does not occur due to the failure of any part of the tree. Hmm...

Risk vs. Hazard

In the past arborists and foresters have used the term hazard assessment to describe the process of inspecting and evaluating thestructural condition of trees. In recent years, there has been concern that the term hazard has unnecessarily negative connotations. The trend now is to identify the process as tree risk assessment.

So, what is the distinction between risk and hazard?
Risk: The potential for injury or damage due to tree failure.

Risk assessment: The process of evaluating the degree of risk, the likelihood that a tree or tree part will fail and cause injury or damage.

Hazard: The presence of a condition that is likely to cause injury. In a risk assessment, a tree is hazardous when the potential for injury or damage due to tree failure exceeds a threshold that is defined by the tree owner or managing agency.
 
In this definition then the roots that may heave a section of sidewalk and create a trip potential would be a hazard.

Also, Hazard then includes an owner or managing agency risk tolerance threshold making it a subjective evaluation vs. objective.
 
I think hazards are virtually always analyzed subjectively because very little methodology provides for evaluations that can be compared.

Scaler models (ie. stem size 1-4, target 1-4 etc.) do not allow for good comparisons and do not provide anwers that do not require interpretation. The tree pulling tests do provide definitive numbers that can be compared and do not require inerpretation. I am not sure if at the moment I can think of any other tests/methods that do this.
 
OK it seems that I have found 8 pictures that I have regarding this site that show pretty well whhat we are looking at. I need to figure out how to export them from outlook to tree buzz now. Anyone?
 
As attachments in outlook you should be able to "save file as" then put them in your photo folder, and manage them from there..no?

The point about Hazard and Risk definitions and confusion is spot on. Courts seem to prefer to lean on OH&S definitions and this works for us too.

Hazard-A hazard is any source of potential damage, harm or adverse health effects on something or someone under certain conditions

Risk-The chance or probability that a person will be harmed or experience an adverse healtheffect if exposed to a hazard. It may also apply to situations with property or equipment loss.

So when I'm assessing tree risk I'm providing very specific info on what the risk is to the client, their property and others from their tree...recognising that all trees contain hazards of some kind...all my tree risk assessment are target driven, not defect driven. It is as mrtree rightly points out influenced very strongly by the subjectivity of the Arborist, and their knowledge and experience of the trees in their area.

There are some attempts to reduce somewhat the influence of that subjectivity QTRA is one such attempt, but of course there's still a heap of subjectivity in it. I do use QTRA from time to time in my tree risk assessments.
 
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...all my tree risk assessment are target driven, not defect driven. I do use QTRA from time to time in my tree risk assessments.

[/ QUOTE ]Do you think QTRA quantifies risk to a reasonable degree? I've looked it over but never actually used it.
 
How does this account for the variability of the owner/agency's risk tolerance? How would you minimize that subjective element in quantifying?
 
I think the arborist needs to provide information/analysis to the owner and let the owner determine what level of risk they are comfortable with. This is a real problem, I had one City of Toronto who said that a service drop to an elderly women's house was not important, its not like this is a school yard, he then said she should move if she did not like the (hazardous) tree.

This is interesting because he is a 50ish able body person, the homeowner was a healthy 70+ women. If the tree tore her service drop then she was in some trouble, but think if she had a husband at home on a ventalator, then her risk tolerance would drop.

I think we as arborist can state a tree is high or low hazard and presents a high or low risk, but it is the homeowners job to present their position to the municapility. We can create replanting plans for a person who wants to removal a beautiful healthy tree but it is hard for us to argue removal for the homeowners purpose if our analysis does not indicate a high level of hazard.
 
So the owner's risk tolerance is really based on some objective elements vs. feelings or misinformation.

In the case of a beautiful healthy tree the analysis could be based on the whether the species is desireable, e.g., invasive non-native.

I wonder which of the city's people you were dealing with there Mrtree?
 
Shall I be bold an say .... No. But I will say that many live in an "ivory tower" and are not reasonable. It is interesting that many of the city inspectors for private, ravine and street trees have no clue about arboriculture, hazard analysis, ID etc. There are a number that I am sure have no qualifications for their job. I actually had one who would not believe they were looking at Castenea mollis, not Castenea dentata. They intended on shutting down the project because they thought it was a rare species. Oh don't get me going.

As for customers risk tolerance. Hopeful the arborist has been able to provide information that would be replicated by another arborist, as you say objective elements. There would still be the issue of "feelings" coming into play. Think about if you tell an Italian in Woodbridge the tree is safe but they say its got to go, the real reason being they are from a culture that reveres the sun and fresh produce from the garden. Although not specifically risk tolerance, it is tree tolerance. OR suppose you tell a person in the Annex (a part of Toronto) that their tree is fine and low hazard and presents no risk. Their risk tolerance may be low because a neighbours car was recently crushed by a falling tree. This is the type of information that the customer should forward.
 
Yep, been there done that. Adds to the time involved in the job but usually worth it.

The inspectors are often more interested in CYA then anything else.
 
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