RPZ help

[simonm]

what should the root protection zone be for a mature copper beech?

[Mark Bolam]

For me I'd go canopy width +1m.

 

Builders would probably go butt + 1".

 

Hama will be along shortly to give you the correct answer.

[simonm]

how do you work rpz's out? ive never had anything to do with them before

[Andy Collins]

Approx 12x dbH IIRC, but take into consideration the shape of the crown, if there is a swell in a certain direction then follow that shape. So if dbh is 1foot, then 12 feet radius from the butt. If that makes sense. I think there is a link somewhere on here to a slightly more tech version.

http://www.blackburn.gov.uk/upload/pdf/area_needed_4_trees_20061208092654.pdf

Edited August 9, 2012 by Andy Collins

[Pete Mctree]

I never did find any evidence where that calculation came from Andy ( anyone help please )

Seems very random & does not take into consideration drip-line, soil type, surface type/permeability etc

To try and utilise a formula seems limiting

[Andy Collins]

I think Paul (Barton) posted a better thing which showed a more realistic Root Area diagram, but at least the 12 x dbh is what the planning Depts go by so it do for me at the moment. Don't forget, KISS, make it too complex to work out and people won't bother. most developers seem to find the 12x too complex to work out as it is, and revert to Mr Bolams theory.

[ScottF]

BS5837 prescribes a figure of 12x stem diameter at 1.5 above the ground, but it really is a rule of thumb. As Andy points out you should consider all the on-site factors that are visible and factor those in. Was of the more important ones I consider is the age-class of the tree, so I'd allow for disturbance closer to a young tree than an old one; not because the rooting area of a young tree is necessarily smaller, but rather because older trees don't recover from damage as readily.