08/1787 - Response to Information Request [As Published] · 132008.1787

Scahaven Development Pty Ltd- 9-19 Hastings Strect Noosa QLD 4567 16

 

 

4.3.3 Trunk Space

5.1

5.2

As teces growth so to does trunk girth and the development of trunk flare at the
base, and in some situations the development of buttress roots. Typically the
trunk flare will be 2 to 3 times the diameter to the DBH on a mature tree,
therefore a tree with a 500mm DBH will have a trunk flare of up to |.5 metres.
Added to this equation is the zone of rapid taper that develops from the major
woody roots. The zone of rapid taper will be influenced by both tree species
and soil type on the site.

The interaction between the trunk flare and surrounding pavement is usually
the main cause of disturbance and uplifting of the pavement. Designs in the
opening sizes in the pavement for trec planting and the type of pavement
around those spaces are critical to minimising future conflicts. An example is
a design that allows removal of pavement to accommodate trunk expansion
over time (Urban 2008, page 273-4, incl Fig 2.5.24).

Included in this requirement for design of tree plantings, is the use of tree
grates. Tree grates are generally considered a major problem for the long-term
strect tree (sec photo No 8). Recently some citics (New York, USA) have
started to ban the use of tree grates.(Urban 2008, page 276-8).

Conclusions

Existing Tree Retention

Given the impacts on the existing site from the proposed development design
and its construction, there is no way to retain the five trees specified by
council in.a long term healthy and structurally sound condition. The major
impac will come from big changes in surrounding soil and the removal of

é ave'modifiéd root growth. These impacts are then
coimipoun ed by thet fiw strictures arid pavement. At best the trees would
sutvive,in a poor and decliding condition, therefore no long-term viability
would be achieved.

 
    

The existing and newly planted strect trecs will most likely require replanting
at the end of the construction. Currently the retention of the Ficus benjamina
isn’t recommended, as the species is inappropriate for the space available and
the recent renovations have caused problems for the tree. The best option is to
remove and replace the strect trees in conjunction with designs that increase
soil volume, stormwater collection, and increased planting arcas, thus creating
a better outcome for street tree plantings.

Design Limitations

The new podium with its fragmented planter box beams represents only a
minor limitation to tree establishment. The planting of trees underneath open
spaces between planter boxes would require only the minimum amount of
dircctional pruning and maintenance to minimise conflict between the trees
and the planter boxes.

 

Leaf and Limb Horticultural Consultancy
Prepared by Samuel Cowie 29" of January 2009

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