Trees and wind resistance

[jhoek]

Hello,

We had a tall silver maple fall on our car during a storm this September. We are now fighting with the city of London (Ontario, Canada) re. the trees condition. The tree was decayed inside, but we need some way to prove that the wind alone would not have been enough to snap a healthy tree of its size.

Does anyone know of any density/ wind resistance formulas?

 

Thanks!

[Stephen Blair]

Before and after pics of the tree and a cross section of the rot within the stem would help.

[woodyguy]

I would have thought the most relevant thing was the fate of surrounding trees.

If the whole street of trees went down before the wind then clearly that was exceptional. If your tree was the only one and is rotten, then you've proved your point surely?

[treequip]

This would be a good place to start

 

http://www.urbanforestanalytics.com/sites/default/files/pdf/bond_tR.pdf

[treeseer]

Here's an 11-page bibliography; knock yourself out: http://auf.isa-arbor.com/request.asp?JournalID=1&ArticleID=185&Type=2

 

all trees have decay. Your fight with the city sounds quixotic. Pics would help.

[treequip]

Here's an 11-page bibliography; knock yourself out: http://auf.isa-arbor.com/request.asp?JournalID=1&ArticleID=185&Type=2

 

all trees have decay. Your fight with the city sounds quixotic. Pics would help.

 

That's a tad harsh, I don't know how it works in Canada but if the city have been negligent in their tree management surely they are in breach of a duty of care to others?

 

I am a little confused at the direction the OP is taking to this situation.

 

Benchmarking what a healthy tree would withstand is an approach I haven't seen before.

 

In my experience (which is limited to UK law) the onus is on the failed tree.

[farmer rod]

 

In my experience (which is limited to UK law) the onus is on the failed tree.

 

does that mean that if a tree falls on something, then the landowner is liable for the cost of putting it right?

[woodyguy]

No not if they had given due attention to inspecting the tree and any defects weren't apparant. But if this tree was obviously rotten and they should have known that through regular inspection and removed the hazard, then yes they are liable.

[daltontrees]

To refine the point made by others, in UK law if the harm or damaged caused by the tree's failure was reasonably foreseeable then the owner is negligent and liable.

 

As ever the difficulty is foreseeing. Foreseeing a car being there might not be that hard. Foreseeeing that a tree falling on it would damage it isn't that hard either. Foreseeing the tree falling is the tricky bit. If the rot wouldn't have been apparent to a reasonably skilful inspector, liability would be hard to prove. If the rot was apparent, it still might not have been enough to cause concern. But if the rot was extensive and the tree's failure was inevitable (I think the ISA system uses the word 'imminent') the owner is liable. Somewhere in the middle is a degree of decay that takes the risk from acceptable to tolerable and then another degree that takes it to unacceptable. If the decay resulted in unacceptable risk the owner is liable. If it resulted in tolerable risk the owner would have to show why he tolerated it despite the risk. That's the UK situation anyway.

 

No-one yet has mentioned t/r ratios. That might be a good way of trying to quantify the residual strength. After all, if one is approaching the assessment (even retrospectively) as a VTA, the third stage is estimating the strength of the remaining parts. t/r ratio is part of the toolbox.

[felixthelogchopper]

Anybody know how the law is applied in Canada? I know there is some common ground with the UK legal system but I don't know how far the comparison goes.