UKTC Archive

RE: Draft Australian Standard - Protection of Trees on Development Sites

Subject: RE: Draft Australian Standard - Protection of Trees on Development Sites
From: Burke Nick \(DEL\)
Date: Dec 12 2008 08:20:19
'I hope I am right in supposing that the structural root zone radius is
13.44 X the DBH, {nominal 1m diameter  X 50 X 0.42 X 0.64 = 13.44}
rather than the 6 to 15 X DBH for the Australian RPZ  and the 12 X DBH
for BS5837 RPZ, though it says in the definition at 1.4.7 ''this zone
considers a tree's structural stability only, not the root zone required
for the tree's  vigour and long-term viability, which will usually be a
much larger area."   - even though the largest RPZ for mature trees is
15 X DBH as a radius.'


I took this equation to be similar to Matthecks VTA windthrow formula.
If you times out 13.44 against a DBH of say 60cm you get a structural
root zone of 8.06 yet if you follow the curve of the chart in the
standard you should have  an SRZ of 3m. My understanding of this is this
is the minimum amount of root that can be left before windthrow will
occur (parks and gardens not street trees etc) I think. The O.42 should
be like squared only I cant get outlook to write it like that.

Nick Burke
Planning Officer - Arboriculture
Environmental Planning,
Development Services
Sheffield City Council,
Howden House
1 Union Street,
S1 2SH

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