Approved Plans & Document OPW21-0272

DETERMINING THE ROOT PROTECTION ZONE

The purpose of the RPZ is to protect the area of roots required to maintain the tree’s vigour and stability
during the development process and into the long term. The RPZ is calculated for each tree based on its
age class and vigour class. Each tree may be fenced off to form an enclosure with the tree at the centre,
or an existing structure may be utilized, being retained such as a wall or fence.
Table 2 provides the means for determining RPZ based on the age and vigour of the tree, as assessed by
the project arborist.
The minimum radius of the RPZ is determined by multiplying the DBH, in metres, by the appropriate
multiplier, given in Column 3 of Table 2.


                                              TABLE 2
                                   CALCULATING THE MINIMUM RPZ
                             (EXCEPT FOR PALMS, CYCADS AND TREE FERNS)

                    Tree Age                         Tree Vigour                  RPZ radius (M)
  Young trees (age less than 20% of life     Good Vigour                             6 x DBH
  expectancy in situ)
                                       Poor Vigour                                    9 x DBH
  Mature trees (age between 20% and 80%Good
                                       of Vigour                                      9 x DBH
  life expectancy in situ)
                                       Poor Vigour                                   12 x DBH
  Over mature trees (age greater than  Good Vigour                                   12 x DBH
  80% of life expectancy in situ)
                                       Poor Vigour                                   15 x DBH

 NOTES:

 1.   Radial distances are measured from the centre of the stem at ground level.

 2.   The RPZ distances in this table are based on a good species tolerance to site disturbance. There
      are no scientific data of tree tolerances for Australian conditions.

 3.   No tree should have RPZ less than 2 m or greater than 15 m. The RPZ of palms and other
      monocots, cycads and tree ferns must be 1 m outside the dripline edge of the crown.




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