Cannonball Tree - Quebec | Death by Numberwang?

2021-11-25 8:43 AM | Admin (Administrator)

This tale about the felling of the famous Cannonball Tree in Quebec because the risk was too high has some incongruous tree risk elements to it.

Cannonball Tree | Quebec

We've not been able to get hold of the reports behind this decision. Only what's in a Press Release and accompanying PowerPoint.

Cannonball Press Release

Cannonball PowerPoint - has been through translation software from French to English.

These are the main curiosities.

1) The range of risk is estimated (sic) with QTRA as being between 1 in 35 and 1 in 526. Both these two and three significant figure risks values are so accurate for a risk that has so much uncertainty, they're not credible.

QTRA Cannonball Tree Quebec

2) The two tomograms from 2009 and 2020 in the PowerPoint are clearly from different heights. As ever, the tomograms appear to undervalue the all the important outermost wood which carries the most load, and is often the strongest and stiffest part of the tree.

Tomography Cannonball Tree Quebec

3) It looks like 73% of the cross section decayed is beyond some kind of threshold, which isn't explained. There's no sound basis for making a decision about the safety factor of a cross-section in a tree based on the percentage decayed without considering the wind load, geometry, and material properties. 


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