UKTC Archive

RE: critical wind-speeds for tree failure

Subject: RE: critical wind-speeds for tree failure
From: Jim Quaife
Date: Oct 12 2017 11:12:24
For many years now we have indicated Force 8 on the land-based Beaufort Scale 
(handy because many of the indicators refer to trees) as being a speed which 
should prompt a check of trees we have identified.  This was a benchmark 
arrived at by a consensus of a gaggle of arbs over a few years, but of course 
it doesn't account for gusts, and nor can it possibly take account of the 
actual individual vulnerability of a tree or its oscillation movements.
In short Force 8 is probably "wrong", but it is rather more useful to a 
client than the vagueness of "have a butcher's if it's a bit windy" approach.
We have never been challenged about it, but then again how many trees blow 
over or fracture?  We have our standard caveat paragraph which I have 
published on and off for 20 years or so, so I may as well paste it below.  
(Before the howls of derision start I did construe it with a QC's opinion - 
and that wasn't cheap!). Please bear in mind that legally it - using the 
words of the QC - isn't worth the paper it is written on, but it sets the 
scene and provides guidance and perspective to the client.  In the event of a 
court claim the court would decide what is a reasonable duration period for 
my opinions - I can't divest myself of my legal responsibilities just by 
saying so!
Jim
The statements made in this Report do not take account of the effects of 
extremes of climate, vandalism or accident, whether physical, chemical or 
fire.  Quaife Woodlands cannot therefore accept any liability in connection 
with these factors, nor where prescribed work is not carried out in a correct 
and professional manner in accordance with current good practice.  The 
authority of this Report ceases at any stated time limit within it, or if 
none stated after two years from the date of the survey or when any site 
conditions change, or pruning or other works unspecified in the Report are 
carried out to, or affecting, the Subject Tree(s), whichever is the sooner.
-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
[mailto:uktc-request@xxxxxx.tree-care.info] On Behalf Of Alastair Durkin
Sent: 12 October 2017 11:58
To: UK Tree Care
Subject: RE: critical wind-speeds for tree failure

Hi Rupert

This was from the 2017 AA amenity conference in Exeter:

https://www.trees.org.uk/Amenity-Conference/Wednesday-Speakers-2017

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
[mailto:uktc-request@xxxxxx.tree-care.info] On Behalf Of Rupert Baker
Sent: 12 October 2017 11:23
To: UK Tree Care
Subject: critical wind-speeds for tree failure

Hi collective,

I googled this term when puzzling over a request to suggest a critical wind 
speed above which a woodland should be closed;  it came up with

https://www.trees.org.uk/Trees.org.uk/media/Trees-org.uk/Documents/Conferenc
e17/WED-08-Prof-Steffen-Rust.pdf which appear to be a powerpoint presentation 
from this year.  Now the main address is the AA;  anyone know which seminar 
or W.H.Y. this came from?

The authors/presenters are Steffen Rust, Lothar Gocke (with an umlaut on the
o) and Franziska Jachning



All the best



Rupert




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The UKTC is supported by Bosky Trees arboricultural consultancy
http://www.boskytrees.co.uk/