UKTC Archive

RE: critical wind-speeds for tree failure

Subject: RE: critical wind-speeds for tree failure
From: Jim Quaife
Date: Oct 12 2017 14:28:23
I attach the Land-based Beaufort Scale as an appendix.

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
[mailto:uktc-request@xxxxxx.tree-care.info] On Behalf Of Paul Muir
Sent: 12 October 2017 15:22
To: UK Tree Care
Subject: RE: critical wind-speeds for tree failure

...and I was suggesting that it is preferable to use the observable signs one 
would expect to see during a Force 8 storm event (if that's what you've 
settled on to advise your client with) rather than the equivalent wind 
speeds, or even the term "force 8" for exactly the reasons you state 
Jim...because what does force 8 mean to the layman? They might take the 
quoted wind speeds and struggle with translating that to an action...with 
many pitfalls available in the process.



Paul Muir
Senior Arboricultural Consultant / Contracts Administrator Treework 
Environmental Practice
Mobile: 07966 XXXXXX
Head Office:  0117 XXX XXXX
www.treeworks.co.uk

Monarch House, 1-7 Smyth Road, Bedminster, Bristol, BS3 2BX


Treework Environmental Practice Covers the UK

London and South East  – Birmingham and Midlands – Bristol and South West – 
Wales – Manchester and North

Treework Environmental Practice is the trading name of Treework Services Ltd.
Registered Office & Place of Registration: Treework Services Ltd, Monarch 
House, 1-7 Smyth Road, Bedminster, Bristol, BS3 2BX

Reg No.: 1621606
VAT No.: 397 XXXX XX
  
This email including attachments is intended for the addressed recipient 
only.  It may contain confidential information and may be subject to legal, 
professional or other privilege. It must not be copied, disclosed or used by 
any other person.  If you are not the intended recipient, please notify the 
sender and then delete from your system immediately. 

Treework Environmental Practice does not guarantee the attachments or 
enclosures are secure or virus-free.


-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
[mailto:uktc-request@xxxxxx.tree-care.info] On Behalf Of Jim Quaife
Sent: 12 October 2017 14:43
To: UK Tree Care
Subject: RE: critical wind-speeds for tree failure

Just bear in mind folks the recipient of a report.  He, she or it will read 
the report but the first question is - so what?  They want to know what to do 
in laymen's terms and the Beaufort Scale is designed for lay people.  It is 
for guidance.
We arbs need to understand all we can, but there is no need to over-think 
things for clients. Force 8 has never been challenged as a benchmark and it 
is clear.  If we bung in a long paragraph explaining all the variables - none 
of which are predictable - are we actually  answering the "so what" question?
Don't get me wrong, the uktc discussion are useful, but the only reason any 
of us is here (even TOs) is because someone is paying us to provide a 
reasoned and understandable opinion and course of action.  I settled on Force 
8 a long time ago to avoid the arm-waving. 
Jim

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
[mailto:uktc-request@xxxxxx.tree-care.info] On Behalf Of Paul Muir
Sent: 12 October 2017 14:24
To: UK Tree Care
Subject: RE: critical wind-speeds for tree failure

Given the descriptive origins of the Beaufort scale, the fact that a 
particular part of the scale is equivalent to a range of wind speeds, not a 
particular speed, and that a description of a particular wind event in 
relation to the wind profile adjacent to a tree is pretty complex and open to 
all sorts of errors and misunderstandings I'd tend to steer clear of setting 
any specific wind speed in this context.

All wind events are defined by an average and a gust speed, so whilst the 
Beaufort Scale doesn't list the gust speeds in the table, there will be a 
gust speed associated with the averages that are presented. Actually a storm 
event will have different average and gusts speeds as it travels across a 
land mass from the sea (there's a wind zone map in BS6399-2 1997, and I'm 
sure foresters are familiar with this, or similar zone maps), and both the 
average and gust speeds are further affected by the roughness category of the 
land preceding the object within the path of the wind event. All of which 
means that there's a lot of uncertainty about the relationship of the wind 
speed that is measured at a measuring station, what it will be at a site, and 
how this relates to the weather event on a national or regional scale.

All of which means that the text that is at the core of the Beaufort Scale, 
describing the observable effects on trees and tree crowns, seem far more 
appropriate and useful, and far less likely to be open to significant errors 
or misinterpretation. Setting Force 8 as a threshold means one closes a site 
when the winds are strong enough to break twigs. For this observable outcome 
to occur at a sheltered site in comparison to an exposed site would require 
different wind speeds at your nearest weather station. I'd say the observable 
signs were more important in relation to the likelihood of tree failure.



Paul Muir
Senior Arboricultural Consultant / Contracts Administrator Treework 
Environmental Practice
Mobile: 07966 XXXXXX
Head Office:  0117 XXX XXXX
www.treeworks.co.uk

Monarch House, 1-7 Smyth Road, Bedminster, Bristol, BS3 2BX


Treework Environmental Practice Covers the UK

London and South East  – Birmingham and Midlands – Bristol and South West – 
Wales – Manchester and North

Treework Environmental Practice is the trading name of Treework Services Ltd.
Registered Office & Place of Registration: Treework Services Ltd, Monarch 
House, 1-7 Smyth Road, Bedminster, Bristol, BS3 2BX

Reg No.: 1621606
VAT No.: 397 XXXX XX
  
This email including attachments is intended for the addressed recipient 
only.  It may contain confidential information and may be subject to legal, 
professional or other privilege. It must not be copied, disclosed or used by 
any other person.  If you are not the intended recipient, please notify the 
sender and then delete from your system immediately. 

Treework Environmental Practice does not guarantee the attachments or 
enclosures are secure or virus-free.

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

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




--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

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


Please don't print this e-mail unless you really need to. Save paper.

Visit http://www.tandridge.gov.uk for information about services, online 
forms, payments and much more.

________________________________
IMPORTANT: The contents of this email and any attachments are confidential. 
They are intended for the named recipient(s) only. If you have received this 
email in error, please inform the sender immediately and do not disclose the 
contents to anyone or make copies thereof.

This message has been scanned for viruses.



--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

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



--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

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



--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

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



--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

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



--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

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



-- 
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

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