Land disturbance occurs when the soil and covering vegetation is removed or disturbed. It includes excavating, infilling, recontouring, earthworks, trenching, and quarrying.
Land disturbance can be a result of road works, recontouring for subdivision, excavation of building foundations, retaining walls, trenching of underground services - anything where ground is moved or altered.
Land disturbance can have serious negative effects - soil loss or damage, soil instability, sediment mobilisation and subsequent deposition and contamination of waterways.
Such disturbances may adversely affect natural ecosystems or impact archaeological sites.
The Separation Point Granites are readily eroded when exposed. Particular care is needed during earthworks and with stormwater control.
Here we provide details of the location and properties of Separation Point granites.
The Separation Point granites are a strip of granitic bedrock about 10 kilometres wide that extends for over 100 kilometres from Abel Tasman National Park in the north to Mt Murchison in the south.
At the land surface this rock is deeply weathered. This weathered surface can be up to several metres in depth and is extremely erodable and readily breaks down to its constituent components forming a coarse sand. It is sand derived from these rocks that form the golden beaches of Abel Tasman National Park.
Because of the highly erodable nature of the Separation Point Granites particular care is needed when undertaking any form of land disturbance. In particular, all stormwater needs to be appropriately controlled and any areas of exposed soils stabilised.
The extent of the Separation Point Granite terrain is mapped as Land Disturbance Area 2 in the Tasman Resource Management Plan planning maps. There are specific rules pertaining to land disturbance activities undertaken on this geology.
The undertaking of land disturbance activities is controlled by rules in the Tasman Resource Management Plan (TRMP). Land Disturbance activities can range from minor vegetation removal to large earthworks associated with major subdivision projects. Some activities may be undertaken as a Permitted Activity subject to complying with the relevant rules within the TRMP, whereas others may require a resource consent.
The land disturbance rules in the TRMP are found in section 18.5. Further detail on the issues, policies and objectivs underlying these rules are in chapter 12 of the TRMP.
Land disturbance activities often result in the mobilisation of sediment that inevitably ends up in waterways if adequate control measures are not adopted. There are specific rules in Tasman Resource Management Plan that address sediment control associated with land disturbance.
There are a range of land disturbance practices and sediment control measures available to limit the impact on the environment. The Council's Engineering Standards contain guidelines for erosion and sediment control. Additional detail can be found in Auckland Council's Erosion & Sediment Control - Guidelines for Land Disturbing Activities in the Auckland Region (Technical Publication 90).
If you are considering undertaking land disturbance activities and require further information, please contact Council's compliance officer: