18Slope limits and other restrictions on site preparation operations

18 Slope limits and other restrictions on site preparation operations

18 Slope limits and other restrictions on site preparation operations

(1) Slope limits for mounding, line ripping and spot cultivation are set according to erosion hazard, which is determined on a combined reading of rainfall erosivity and class of soil regolith stability.

Note—

The classes of soil regolith stability referred to in this Division (R1, R2, R3 and R4) are defined in the Dictionary to this Code.

(1A) Mounding must be constructed on the contour with grades that will not result in erosion of the mound channel or mound discharge point or erosion due to overtopping of the mounds.

(2) Subject to subclause (3), mounding, line ripping and spot cultivation of the plantable area may be carried out only if the slope of the plantable area is within the slope limit set for an area with the combined rainfall erosivity and class of soil regolith stability of the plantable area, as set out in the Table in this subclause to which the relevant operation relates—

Slope limits for mounding

| | | | R1 | R2 | R3 | R4 | | | | | 0–1999 | 30° | 20° | 25° | 10° | | 2000–3999 | 25° | 15° | 20° | 5 | | 4000–5999 | 25° | 10° | 20° | no mounding allowed | | 6000 + | 20° | 5° | 10° | no mounding allowed |

Slope limits for line ripping and spot cultivation

| | | | R1 | R2 | R3 | R4 | | | | | 0–1999 | 30° | 25° | 30° | 15° | | 2000–3999 | 25° | 20° | 25° | 10° | | 4000–5999 | 25° | 15° | 25° | 5° | | 6000 + | 25° | 10° | 20° | 5° |

(3) The slope limits apply only to the slope of the majority of the plantable area, that is, individual areas of the plantable area of up to 50×50 metres may exceed the limit by up to 5° and still be included in the operation concerned, provided the total of such areas does not exceed 5% of the plantable area.

(4) Runoff water flowing from mounds must be directed onto a stable area, or a structure, capable of filtering runoff water and trapping sediment.

(5) Machinery used for site preparation must not be operated on a site being prepared if the soil on the site is saturated or if surface runoff is occurring. (Surface runoff occurs when rain is not immediately absorbed into the soil and becomes overland flow.)

(6) Establishment operations must not cause impeded or concentrated water flow that results in soil erosion within drainage depressions.