Approved Plans OPW21-0038

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               Good Vigour                     9 x DBH
  80% of 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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