The Helliwell system

[AA Teccie (Paul)]

Am I right in thinking the Helliwell system was originally developed to assess the amenity value of a tree using a scoring system, hence was often used for evaluating amenity on proposed TPO trees, rather than as a monetary valuation system whereas CAVAT was the opposite way round.

 

Don't know the significance of such but perhaps has some bearing.

 

Cheers..

Paul

[daltontrees]

What systems are people using most Jules? I haven't looked at the Helliwell system since college.

 

I think by sheer volume the mostly used is CTLA, which is at the core of iTrees.

[daltontrees]

Am I right in thinking the Helliwell system was originally developed to assess the amenity value of a tree using a scoring system, hence was often used for evaluating amenity on proposed TPO trees, rather than as a monetary valuation system whereas CAVAT was the opposite way round.

 

Don't know the significance of such but perhaps has some bearing.

 

Cheers..

Paul

 

That's what I meant by Helliwell being a comparative system rahter than an absolute one. It originated as you say to quanmtify amenity, then it was later monetised. And that's the flaw with it, the points are multiplied bya published £ per point All trees valued by the Helliwell system are valued by a committee of the AA that comes up with that £ per poiint figure. There is no objective basis for it.

[daltontrees]

What would you say are the main flaws of the system?

 

See my reply to Paul. There is one main flaw, and as such Helliwell valuiations cannot be considered valuations in any conventional sense. CAVAT carries an equally fundamental flaw.

[Jon Heuch]

I think by sheer volume the mostly used is CTLA, which is at the core of iTrees.

 

Ah ha! No it is not......well it is confused and confusing. I believe CTLA is widely used in the US. I Tree incorporates a CTLA valuation (the software used to use the 8th version rather than the 9th, but being non-transparent it is difficult to tell) but the main part of it is not based on CTLA.

 

You need to read......well, it's pretty well hidden, so I can't point you to a single document. The I Tree manual (there are several and a new version comes out from time to time) tells you how to collect data in the field, collate, process etc but tells you next to nothing about value and valuation.

 

I Tree produces two types of valuation based on the same field data: it produces values for a small number of ecosystem services (carbon, water retention, pollution reduction) and quite separately uses CTLA to produce a replacement/structural value. If you don't read the reports carefully, there is an implication that in some way the two are linked - they are not. Journalists and the media however are happy to pick up the CTLA structural value and relate it to ecosystem services......which is politically useful but just plain wrong. However, that is not the message people want to hear!

[Jon Heuch]

What would you say are the main flaws of the system?

 

So you need an answer for your course work?

 

I would refer you to RICS and their valuation framework provided by the Red Book........well that might be a bit much to take for a college exercise. RICS starts a valuation exercise off with identifying a "basis" appropriate for the exercise. A basis is a statement of the fundamental measurement assumptions of a valuation......it's a useful definition for a college essay! The question for the Helliwell system (and for CAVAT) is what is its "basis"? What makes a Helliwell point worth anything and therefore how does a tree have any value at all? Of course, there isn't one...at least not in any transparent manner.....trouble is, there wasn't one when the system was first introduced (The Tree Council have been through their records and can't find one!) and every year any adjustment for inflation just builds upon the previous poor foundation.

 

The basis for CAVAT is slightly stronger in that it attempts to work off "cost" and then "replacement cost" but it is weak on the depreciation bit (depreciated replacement cost being a recognised RICS basis, but the least preferred, to be used as a last resort) and has failed to learn the lessons of CTLA in that it does not use the adjustment for trunk formula (leading to very large values for large trees).

[daltontrees]

Ah ha! No it is not......well it is confused and confusing. I believe CTLA is widely used in the US. I Tree incorporates a CTLA valuation (the software used to use the 8th version rather than the 9th, but being non-transparent it is difficult to tell) but the main part of it is not based on CTLA.

 

You need to read......well, it's pretty well hidden, so I can't point you to a single document. The I Tree manual (there are several and a new version comes out from time to time) tells you how to collect data in the field, collate, process etc but tells you next to nothing about value and valuation.

 

I Tree produces two types of valuation based on the same field data: it produces values for a small number of ecosystem services (carbon, water retention, pollution reduction) and quite separately uses CTLA to produce a replacement/structural value. If you don't read the reports carefully, there is an implication that in some way the two are linked - they are not. Journalists and the media however are happy to pick up the CTLA structural value and relate it to ecosystem services......which is politically useful but just plain wrong. However, that is not the message people want to hear!

 

I did half of the Glasgow iTree survey, it put monetary value on hundreds of individual trees. Conversely, I have used Helliwell fo about 20 trees. I will never use CAVAT. I have played with CTLA but have resorted to first principles of DRC in preference to using it fully. So for me iTrees is the commonest.

[Victor]

Thank you guys for your time and replies. Very helpful.

[Paul Cleaver]

Did you mean 'flawed'?

 

wess

[Gary Prentice]

It's just come to my attention that Rodney Helliwell passed away on the 23rd of February.

 

There's a small piece here about his background http://www.rodneyhelliwell.com/background.php and the announcement is also on the Hortweek website (sorry no link)