BS5837 categorisation

[Paul Barton]

Ok, not strictly a legal issue but this part of the forum seems relevant to the planning process...

 

I have recently started doing some work with another arboriculturist and we have discovered that we have a slightly different approach in categorising trees on potential development sites. It has got me thinking and re-evaluating my approach - I thought it would be useful to find out how others view it.

 

The 2012 BS states:

"the tree survey should be completed and made available to designers prior to and/or independently of any specific proposals for development" (4.4.1.1).

 

My understanding of this section is that the tree survey should be an objective excercise - the trees should be considered on their own merits, and in the absence of any knowledge of development proposals, in their current context. i.e. are the trees in good condition and do they make a positive contribution to the landscape as it is?

 

But then in section 4.4.2.2 the BS says:

Individual trees, groups of trees and woodlands should be assessed for their quality and benefits within the context of the proposed development, in a transparent, understandable and systematic way. The quality of each tree ...shall be recorded by allocating it to one of four categories.

 

To me this seems contradictory and confusing.

 

So, for example, lets say we are surveying an overgrown plot of land in a residential area. The trees on the site are sycamore, hawthorn and birch - say 5-10 metres tall and around 10-15 years old. They are self-sown trees, growing vigorously and likely to do so for at least 20, maybe 40 years if left alone.

 

To my mind many of these trees could conceivably be categorised as 'B' trees; moderate value trees in their current context. After all, there is nothing wrong with them per se - they have no serious defects and are a long life expectancy.

 

But should these trees really be considered as a material constraint? After all, they are merely young self-sown trees - and probably not 'significant' enough to pose a serious site constraint surely?

 

The table in 4.5 gives a little hint in this direction: the words "unremarkable trees of very limited merit" in category C. But - very little merit in what context?

 

I am always aware that much of what is written in BS5837 reports goes unread (perhaps I am under-selling some tree officers?). My experience suggests that most readers quickly flick through the report and head straight for the tree survey/constraints plan - if there are lots of green and blue trees then beware, but grey trees can go!

 

So, how do you approach using the BS5837 categories? Are you happy with how it works or is the method just too blunt an instrument?

[armybloke]

I have some concerns myself Paul. I will print this off and have a little bit of a think especially as this is my bread and butter nowadays - good thread!

[daltontrees]

The contradiction between 4.4.1.1 and 4.4.2.2 jumped out at me a couple of weeks ago, I have been trying to reconcile the two in my head ever since. So far I have only managed to do this partially by taking the 'survey' of 1.1 to mean no morr than a recording of species size and position of trees. I expect though that this is all a drafting error in the BS and can't be reconciled. I agree that the underlying intention should be for the tree categories to be decided objectively, but this cannot really be achieved meaningfully without the context of the proposed development.

Generally BS5837 is used to manage the planning aspects of a development as they relate to trees. As such the LPA is well used to considering the change not just to the site and its use but to the area around it. Isn't the important thing the amenity provided by the trees as they are (and the extent to which they are or are not currently protected) and the amenity of such trees as are retained, newly planted or pruned (and the extent to which they will be protected)?

If so, there are quite a few things to get the head around. But you would have to write yourself a set of sub-rules that both the client developer and the LPA would have to agree to. Before the trees are categorised. But it could be after they are surveyed?

[oslac]

The British Standard is just that, it is a standard and is generally accepted to be the lead document in relation to trees when considering planning. That said, it is also a load of old billhooks in many respects.

 

The BS appears to be a document which has lost touch with reality and that was brought out during the road show last year when the author explained the ins and outs of it.

 

The caregorisation of trees (the cascade chart) gives a category value to trees but as we all know, development has to go ahead and will go ahead and so the arb consultant is immediately squashed between the needs of the developer and the requirements of the LPA. The catergory rating is based on two values , both of which are subjective. There's the quality value and the remaining contribution value. Both of which must be achieved for any particular category to be applied.

 

The context is another subjective point. Context normally relates to the relationship of the development with its surroundings. So a block of flats in a field has a poor contextual relationship but just about anything in an urban area has a good (or less bad) contextual relationship.

 

All in all, no arb consultant can get it right. The developer sees it one way whilst the TO sees it another. All you can do is what you think is right, stick to your own independent views, be consistant, remember who is paying you and realise that at the end of the day the TO is only trying to save trees for the benefit of the local community.

 

I should think that in a residential or overgrown or self sett situation, the majority of trees will be categorised as C. Which is just as well.

 

By the way, Tree Constraints Plans are a thing of the past. Not mentioned in the BS and only used as an internal design tool.

[kevinjohnsonmbe]

Interesting thread, I'm typing up a report right now....

 

I found 5.1.1 useful in leading my thought process, the trees are only 1 factor in many that contribute to a planning decision. I've been mentally challenging the 'amenity value' tag which seems to be somewhat over applied. There are some appropriate definitions which I've found and they have been useful in supporting a recommendation for removal of a TPO tree - who'd have thought it!

 

5.1.1 The constraints imposed by trees, both above and below ground (see Note to 5.2.1) should inform the site layout design, although it is recognized that the competing needs of development mean that trees are only one factor requiring consideration. Certain trees are of such importance and sensitivity as to be major constraints on development or to justify its substantial modification. However, care should be taken to avoid misplaced tree retention; attempts to retain too many or unsuitable trees on a site can result in excessive pressure on the trees during demolition or construction work, or post-completion demands for their removal.

[Callum]

Hi All

 

I interperate the BS to mean that trees should be assessed in the general context of the site being used for 'development', but that's as far as it goes.

 

The arboriculturist should not be influenced by specific plans or layout design when carrying out the tree survey, because the idea is that the design stage should happen after the tree survey taking into account the constraints posed by the trees.

 

(Although as we all know, the arb usually gets involved after all the plans are drawn up )

[Paul Barton]

There's the quality value and the remaining contribution value. Both of which must be achieved for any particular category to be applied.

 

For me this is another sticking point. I looked at a site yesterday where the best trees were mature Silver Birch. In terms of amenity value they were the most significant trees, but given their relatively short lifespans when compared to the surrounding young Oaks and even Sycamores I didn't feel able to award them a higher retention category.

 

What's particularly odd about this is that TPOs are often applied the other way round - on fully mature trees that have a relatively short-term expected contribution.

 

I do get, and agree with the concept that the planning process should aim to secure long-term benefits for the site but this often conflicts with the present realty of the current visual impact.

 

 

By the way, Tree Constraints Plans are a thing of the past. Not mentioned in the BS and only used as an internal design tool.

 

I think the 2012 BS just re-names the Tree Constraints Plan as 'Tree Survey Plan' now...surely a plan that has the canopy spreads and RPAs of each tree is essentially still a constraints plan

[ScottF]

Trying to stick slavishly to the BS standard is an excellent way of giving yourself a headache.

 

In an ideal world the arb assessment would be carried out prior to any layout being produced and should directly inform that assessment. In my experience, 80%+ of the time the layout arrives as a done deal and we have to try to make the trees "fit" using special construction methods, protective fencing and so on. These are the facts, irrespective of the standard.

 

I've seen excerpts of the standard quoted and referred to in planning appeals and hearings, and any competent brief or planning consultant can deal with these with a conflicting passage from the same standard.

 

In terms of tree life spans I'm always mindful of the typical "life spans" of modern developments- so many of the sites I've looked at recently are redevelopments of sites originally developed in the 70's and 80's, sometimes more recently. I think a nice silver birch, 300-400mm dbh would be an ideal tree for a modern development as it will be in its prime during the ACTUAL working life of the building, would never get too big or cast an overly-heavy shade. In your example, Paul, I think the birches you mention would probably be a better fit to a typical modern development, compared to sycamores or even oaks. Does that make sense?

 

As someone else suggested above, to me the standard provides a rough framework approach for dealing with trees and development and everyone does it differently.

[oslac]

For me this is another sticking point. I looked at a site yesterday where the best trees were mature Silver Birch. In terms of amenity value they were the most significant trees, but given their relatively short lifespans when compared to the surrounding young Oaks and even Sycamores I didn't feel able to award them a higher retention category.

 

What's particularly odd about this is that TPOs are often applied the other way round - on fully mature trees that have a relatively short-term expected contribution.

 

I do get, and agree with the concept that the planning process should aim to secure long-term benefits for the site but this often conflicts with the present realty of the current visual impact.

 

 

 

 

I think the 2012 BS just re-names the Tree Constraints Plan as 'Tree Survey Plan' now...surely a plan that has the canopy spreads and RPAs of each tree is essentially still a constraints plan

 

If the trees have a remaining contribution of less than 40 years, they cannot be given an A category, no matter how wonderful they are. It is not for the arb consultant to rewrite the BS, bend it maybe but not rewrite it.

 

Sustainability is an issue but think about this> The TO has a mature tree happily growing on site, why would he/she allow that tree to be removed and then replaced with a sapling tree with a limited chance of reaching maturity. At the same time, the removal of that tree may allow the developer to cram another house or as usual, another car parking space onto the site and the removal of the tree is essential to maximise profit. The obvious argument is to remove the tree on the grounds of sustainability i.e. the replacement tree will live for 100 years whilst the existing tree will remain for 20 years. You can see the dilemma and as usual, the arb consultant is caught in the middle. I was once called 'the enemy' because I agreed with the council, that a proposed building was too close to a retained tree . . . and that's from my Client.

 

The Tree Constraints Plan has been deliberately left out of the BS as too many TO's were relying on it at the expense of the far more important - Arb Impact Assessment. You are free to provide a TCP to your Client and it would be sensible to do so, however the BS does say that the RPA's should be plotted onto relevent drawings including the site layout plan. So you are right, its a TCP but with a different name.

 

In my view, the BS is OK. It has flaws especially with modern technical solutions to development proposals and it allows the TO to rely on its litteral content rather than seeing the document as a tool. Where I see its greatest failing is that, in a lot of cases, the document is based on subjectivity but wrapped up in objective language and as such interpretation is very variable especially between the TO and arb consultant/developer. That is why poorly qualified TO's with limited experience can cost a developer a lot of money and time over nit picking the detail within the BS rather than looking at the bigger and more holostic picture of the real world.

[Paul Barton]

Trying to stick slavishly to the BS standard is an excellent way of giving yourself a headache.

 

Quite. The clue is in the title isn't it: 'recommendations'. I realise that you can write anything you want in a report so long as you can justify it. What prompted the thread was just the recent experience of working with another arb that has a slightly different approach.

 

In my experience, 80%+ of the time the layout arrives as a done deal and we have to try to make the trees "fit" using special construction methods, protective fencing and so on.

 

Ditto.

 

 

In terms of tree life spans I'm always mindful of the typical "life spans" of modern developments- so many of the sites I've looked at recently are redevelopments of sites originally developed in the 70's and 80's, sometimes more recently. I think a nice silver birch, 300-400mm dbh would be an ideal tree for a modern development as it will be in its prime during the ACTUAL working life of the building, would never get too big or cast an overly-heavy shade. In your example, Paul, I think the birches you mention would probably be a better fit to a typical modern development, compared to sycamores or even oaks. Does that make sense?

 

It does, thanks Scott. As it happens the Birches I looked at where 650mm DBH and 20 metres tall - lovely trees but in my opinion unlikely to exceed 20 years further.