Obvious Tree Risk Features

[Acer ventura]

The Elephant in the Tree

 

Why do elephants paint their toenails red?

 

It turns out elephants don’t need to paint their toenails red to hide in Cherry trees.

 

A hanging branch is so ‘f’ing obvious’, I didn’t include it in the original Obvious Tree Risk Defects* Guide. It's been coming for a while, and I’m now persuaded too many civilians don’t look up and see the elephant in the tree. Looking up is an Arborist and Urban Forester thing.

 

The final nudge came from Rick Milsom (a UK Tree Officer) who shared a tale of a picnicking couple in his patch. Of all the places they could picnic in a park, they chose to do it under a 6m long broken branch on an Ash tree that was hanging on by the skin of its teeth. If they stood up, the tip of the branch was just above their heads.

So, I’ve updated the Obvious Tree Risk Features Guide (v3.2) to include hanging branches. It's released under a creative commons license so you're welcome to use and share and it.  I’ll sort out fitting it into the strategies this week.

 

https://tinyurl.com/y679ucl4

 

* 'Defects', in the original, has been upgraded to 'Risk Features'

 

PS I've updated some of the wording as well.

Edited July 5, 2020 by Acer ventura

[Khriss]

Moment tree almost falls on pedestrians

WWW.BBC.CO.UK

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A falling tree in Ealing nearly collapsed on to pedestrians at a crossroads.

 

 

 

 

The category for this under VALID  ?   k

[Acer ventura]

13 hours ago, Khriss said:

 

 

The category for this under VALID  ?   k

Hi Khriss

 

I saw and shared the dashcam footage on LinkedIn and Facebook yesterday.  There have been some interesting responses.

 

Here's my take on it with VALID's Tree Risk-Benefit Management Strategy.  It's based on the dashcam footage and Google street view images.  So it's made with those limitations.

 

This a 'Very High' level of occupancy (on average more than one person.  Or more than one vehicle.  Or more than person and more than one vehicle).  It would've been managed by Active and Passive Assessment.  There are three levels of Active Assessment.  Basic, Detailed, and Advanced.  If you want more details, there here in the Government section.

 

https://tinyurl.com/y679ucl4

 

Passive Assessment - Risk is Acceptable

If you walked or drove past this tree, there's no obvious tree risk feature to trigger taking a closer look.

 

Basic Assessment - Risk is Acceptable

On foot.  There are no obvious tree risk features.  It looks there has been no recent major infrastructure work within the structural root zone to warrant any concern (weirdly, I know this location well).  I can't see a trigger to go beyond a Basic Assessment to a Detailed level.

 

Detailed Assessment - Risk is Acceptable

From what I can see in the video, I'm not sure a Detailed Assessment, with a sounding hammer, would've revealed the extent of decay in the roots.  There's some uncertainty about this, but the buttressing looks like it's nicely developed for a tree of this size, age, and management history.

 

Advanced Assessment - Risk is Not Acceptable

I think only an Advanced Assessment, involving a Static Load Test, would've established that the tree had a Safety Factor of less than 1.0.  But I can't see a trigger to reasonably justify this.

 

It wasn't THAT windy on Sunday in South Ealing. I wonder whether primary failure happened with the storms we had earlier (or last year), and it's only as the tree's come into full foliage, 4 years (?) into its pollard cycle, that the moderate wind load intercepted by the canopy hit the critical point. 

 

It now presents an interesting problem for the council.  That paving specification at pedestrian crossings might be of concern given how long ago it was done and the root system resembles that of spring onion.

 

Of course, it could be a 'black swan'.  Generally, the chances of regularly pollarded London Plane, with no obvious tree risk features, and no obvious recent root damage, falling are incredibly low.
 

[Khriss]

I certainly would concur on this.

My view off the cuff , Mature tree, V.High target values, no obvious damage or decay in crown or trunk,  previously pruned ( badly ) hard cover for root development,  pollution and salt in growing area.

6monthly inspection after thorough first examination. Expected Safe Lifespan 10 years.

 

Which is just from the image , and trees like that cover most of London.  And I was working in this area for 2 weeks and there are FAR more obvious Hazard tree candidates in Ealing ! Scarey occurrence if 'unforeseen ' fits this tree  ?  K