2022-08-09 Services & Organisation Committee Agenda

SERVICES & ORGANISATION COMMITTEE MEETING AGENDA   9 AUGUST 2022




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SERVICES & ORGANISATION COMMITTEE MEETING AGENDA                                                                9 AUGUST 2022

                                                                                                       Noosa Shire Council
                                                                                    Guiding Principles for Tree Management

                     e   Atree or tree part with the potential to fail;
                     e   Anenvironment that may contribute to that failure; and
                     e   Person or object that would be injured or damaged (i.e. the target and occupancy rate).
                 The following is a general overview of the tree risk assessment process that the arborists follow and
                 methods of determination used when assessing trees on behalf of Noosa Council:
                 Visual Tree Assessment (VTA):
                 Generally, a visual assessment of a tree primarily takes into consideration the tree’s physical attributes,
                 structural condition, health, suitability for the location and weighs that with the rate of occupation and value
                 of the targets beneath the tree that would be struck if failure was to occur onto the target. This takes into
                 account the core risk principal and assesses potential targets and occupancy rate, the likelinood of failure,
                 and the consequences of partial or whole tree failure.
                 Risk Assessment:

                 The framework of the ISA TRAQ is to establish tree risk using a qualitative risk matrix. It encompasses a
                 broad spectrum of questions and criteria which are based on the likelihood of an event occurring and the
                 likelinood of that event impacting a target and the consequences of that impact. It must be noted that while
                 all assessments undertaken are based on the knowledge and principals provided by the ISA TRA, a
                 complete form-filled assessment is not undertaken on every tree as for most trees this is unnecessary.
                 The qualitative risk matrix used by arborists under the ISA framework is attached in Appendix C.
                 The aim of both methods is then to specify mitigation options or arboricultural interventions such as
                 pruning to reduce the overall tree risk rating where required to an acceptable overall residual risk.
                 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 (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 (€.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 — 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.
                 Very Low - Tree removal is recommended. Trees are considered potentially hazardous, very poor
                 specimen, and/or may be an invasive plant.

                 Noosa Shire Council                                                                         5

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