Tree Risk Assessment Qualification (TRAQ) – ISA Best Management Practices

[jomoco]

Seems to me there are tree species that have an inherently high risk of shedding limbs, and species with a much lower risk. Good ole common sense tells me the latter is the appropriate tree species for school settings.

 

Good planning obviates the need for over analyzing and charging the pants off a school district for lame landscaping decisions.

 

Jomoco

[Acer ventura]

I’ve been getting some off-forum emails about this thread. It didn’t occur to me to mention it when I started it, but if you want to join in, have an opinion, or some insight to share, but are too shy or reluctant to post on here then please email or pm me.

 

Warning. This next section can all too easily mess with your head. Not just the values but the words as well. I know it did mine when putting it together. It’s a buttock-clenchingly tedious but necessary exercise.

 

With the range values that we’ve got so far for Likelihood of Impacting the Target and Likelihood of Failure, I’m going to populate the range values in the cells of the Likelihood Matrix for Very likely, Likely, Somewhat likely, and Unlikely.

 

<<Missing matrix>>

 

I’m going do a post each for Very likely, Likely, Somewhat likely, and Unlikely, so they can be referred to separately, and then one for the completed Likelihood Matrix. So, in the unlikely event that you don't find the workings out fascinating, you can skip to the last one if you want, and check back to the other posts if you want to know how the range values were derived.

 

Cheers

 

Acer ventura

Edited May 17, 2014 by Acer ventura
Wrong attachment, and can't figure out how to upload correct on in edit pane

[Acer ventura]

 

Very Likely

Imminent & High = Very Likely

1/1 x 1/1 = 1/1

 

Cheers

 

Acer ventura

[Acer ventura]

 

Likely

 

Imminent & Medium = Likely

1/1 x <1/1 - >1/2 = <1/1 - >1/2

 

Probable & High = Likely

1/1 - >1/2 x 1/1 = 1/1 - >1/2

 

Likelihood range for Likely from the two cells

Highest value in Likely range = 1/1

Lowest value in Likely range = Greater than or equal to >1/2

 

 

Cheers

 

Acer ventura

[Acer ventura]

 

Somewhat likely

 

Imminent & Low

1/1 x <1/2 - ? = <1/2 - ?

 

Probable & Medium

1/1 - >1/2 x <1/1 - >1/2 = <1/1 - >1/4

 

Possible & High

1/2 - ? x 1/1 = 1/2 - ?

 

Probable & Medium Somewhat likely cell, less than <1/1, greater than or equal to >1/4, is the most explicit and clearly defined cell in the Risk BMP.

 

Lowest value in Somewhat likely range will be lower than >1/4 because the lowest values in Possible and Low are likely to be less than 1/2, so I’ve marked it ‘?’

 

Likelihood range for Somewhat likely from the three cells

Highest value in Somewhat likely range = Less than <1/1

Lowest value in Somewhat likely range = Greater than or equal to >1/4?

 

 

Cheers

 

Acer ventura

[Acer ventura]

 

Unlikely

 

Probable & Low

1/1 - >1/2 x <1/2 - ? = <1/2 - ?

 

Possible & Medium

1/2 - ? x <1/1 - >1/2 = <1/2 - ?

 

Possible & Low

1/2 - ? x <1/2 - ? = <1/4 - ?

 

Upper values for Improbable and Very Low not clear, so cannot work out the values for that row and column.

 

Likelihood range for Unlikely from the three cells that can be worked out.

Highest value in Unlikely range = Less than <1/2

Lowest value in Unlikely range = ?

 

 

Cheers

 

Acer ventura

[Acer ventura]

 

The Likelihood of Failure and Impacting the Target Matrix with value ranges.

I've removed the ? for the lower value of Unlikely because it being the lowest of the likely descriptors it has to stretch off to infinity and beyond.

 

Does this make sense? Any comments?

 

I'll move on to the Risk Matrix on Monday and take on board any revisions based on what comments I get back on or off forum.

 

Cheers

 

Acer ventura

[Acer ventura]

you've got to say it in a Yorkshire accent, works much better.

which also highlights the difference's in the understanding of the meaning when international standard English is used.

 

Hi Craig

 

Wouldn't your ranges for 'Likelihood of Failure' be t'will , t'might, t'could, t'unlucky then?

 

Cheers

 

Acer ventura

[Acer ventura]

Still work in progress with the upper values and boundaries of the Likelihood of Failure range Improbable, and Likelihood of Impacting the Target range Very Low, in the Likelihood Matrix. Nonetheless, this is what we know so far about the four Likelihood of Failure and Impact ranges from the Likelihood Matrix, which can now be fed into the Risk Matrix.

 

 

One thing that is readily apparent when the Likelihoods are viewed like this is the ranges are no longer explicit and there are overlaps.

 

The other axis in the Risk Matrix is populated by four rating ranges of 'Consequences', descending in magnitude; ‘Severe, Significant, Minor, and Negligible’.

 

The Risk Matrix cells are partitioned into four risk rankings, descending in magnitude; ‘Extreme, High, Moderate, and Low’.

 

 

The easiest, and probably most important, of the Consequences to have a look at first is a fatality. A fatality is the highest value in the Severe Consequences range, and in terms of probability is 1/1.

 

 

The probabilities for a fatality are the same as they are for the four Likelihood ranges because they are simply multiplied by 1/1.

 

Cheers

 

Acer ventura

 

PS Thanks to whoever fixed my post No.12 on Saturday.

[daltontrees]

Hi Jules

 

Serious answer...

 

Didn't I explain 'why' in the opening post? If not, expand more on what you mean by 'why?', and I'll try to answer.

 

Cheers

 

Acer ventura

 

Sorry for delay in replying, I have been inordinately busy lately.

 

Your original post makes it pretty clear what you would like to do. But it's still not clear why you want to do it. I mean, you are representing the commercial interests of QTRA Ltd., are you not? It wouldn't be the first time Arbtalk has been used for commercial interests, in a way that's partly what it's for, for people in the tree business to help one another. But in so doing the benefits are shared within the business. This research is generally a deserving area of work, and as far as I am concerned you are entitled to ask for people to chip in. I suspect you already have the answer.

 

I sould also explain that I have been working on this issue for about 6 months, covering it as part of a bigger piece of work that at the time you posted last week I was tidying up for submission for peer review and publication. Since then I have been doing 2 big tree surveys and using these as an opportunity to thrash out some concepts in my head regarding quantification of tree risk. One piece of information had been missing, namely a copy of Matheny & Clark's 1994 book, which I got through the post last week. I am glad I waited for it, because the hazard rating it introduced remains the foundation of most if not all proprietary quantitative and qualitative tree risk assessment methods and I was missing some of the perspectives on this that required the whole book and not just the abstracts that I have been using for my draft.