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Compiled Approved plans MCU22/0087.01 & OPW22/0140.01
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Consult Arborist
A PPENDIX 1 - D EFINITION OF T ERMS
The following criteria have been used in the VTA and arboricultural appraisal to gather information and determine
the required management options on the grounds of public health and safety. Measurements are approximate and
made visually by eye unless otherwise stated.
Age Class:
Young: Early-stage of growth, immature size
Early Mature: Fast-growing well-established tree which has not yet reached mature size
Mature: The tree reached its mature size, exhibits slowing growth rates with early stages of naturally forming dead
or dysfunctional wood.
Over Mature: Tree has reached mature size and is unlike to increase significantly in height or mass. Retrenchment of the
upper crown with increased vegetative vitality in lower crown, increased fungal activity and wood decay,
increase colonisation by flora and fauna.
Veteran: Tree with advanced retrenchment, reduced crown size and annual increment growth, extensive hollowing,
crown collapse, low vigour, advance heartwood decay, advanced colonisation by fauna and flora.
Health:
Good: Tree with no defects or disorders which are notable. Full canopy with good colour foliage. Minimal pathogen
damage.
Fair: Tree with minor defects or disorders which are notable. Some dead wood within what can be an unbalanced
canopy, foliage generally with good colour although some discolouration may be present typical of species
in location. Minor pathogen damage.
Poor: Tree with major defects or disorders which are notable. Tree has considerable deadwood present,
discoloured or distorted leaves indicating a further decline of the tree. Detrimental pathogen damage.
Dead: Dead or dysfunctional moribund tree.
Structure:
Good: Tree with good unions and no branch defects. Sound trunk with no / minor defects. Good buttress and root
structure.
Fair: Tree with minor defects or disorders which are notable. Small areas of bark missing. Small cavities or minor
unfavourable branch unions may be present. Minor damage to roots.
Poor: Tree with major defects, large hollows, weak unions and/or problematic damaged roots.
Hazardous: This implies a tree with a major defect that may fail at any time
Protection of Trees:
DBH Diameter at Breast Height - The approximate diameter of the trunk is measured visually in millimetres at a
height of 1.4m.
TPZ The Tree Protection Zone, as per AS 4970-2009 Protection of trees on development sites, is the principal
means of protecting trees on a development site. The TPZ is a combination of the root and crown area
requiring protection to be isolated from construction disturbance so that the tree can remain in a viable
condition. The TPZ incorporates the Structural Root Zone (SRZ).
The radius of the TPZ = DBH x 12
A TPZ should not be less than 2m or greater than 15m (unless crown protection is required).
SRZ The Structural Root Zone, as per AS 4970-2009 Protection of trees on development sites, is a mathematical
calculation of the surface area of protection required to maintain a tree’s stability – a larger area is required
to maintain a tree in viable health. It is only necessary to calculate the SRZ when major encroachment into
a TPZ is proposed.
Tree Retention Value:
The retention value status is based on industry recognised methods of ascertaining the retention value of a tree. The suitability
of the tree for preservation or retention is based on the individual qualities of each tree. By taking into consideration the health,
structural condition, aesthetics, age, size, longevity (Safe Useful Life Expectancy) and ability to adapt to new environments the
viability of the tree can be reasonably determined.
For trees in non-use areas (e.g. Open spaces) where a range in tree quality is appropriate, all trees may be considered suitable,
except for invasive species.
Suitability for Retention/Preservation Categories are:
High: Tree retention is the priority.
The tree has high amenity, heritage and/or environmental value. It is in reasonably good condition (any minor
structural or health problems can be mitigated), has a long life expectancy and can recover from injury or
respond to environmental changes.
Medium: Tree retention is desirable.
The tree is in fair-good condition, is a locally common species, the tree contributes to the aesthetics of its
locality and should survive for many years. The tree may have health or structural problems that can be
mitigated with treatment.
Low: The tree is not considered worthy of special measures to ensure its retention.
The tree is in poor condition with significant defects that cannot be mitigated, has a short Useful Life
Expectancy, or the tree is expected to decline regardless of treatment. The tree has low value in the
landscape or is an undesirable species.
Remove: Tree removal is recommended.
Trees are considered potentially hazardous, very poor specimens, and/or may be environmental or noxious
weeds.
22_12_01_AIA_Thynne_37 Bottlebrush Ave Page 19 of 21
Document Set ID: 24320610
22595441
Version: 1,
2, Version Date: 20/11/2025
25/09/2023
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