Without protection measures, earthworks and other land-disturbing activities can result in greatly increased on-site erosion and sedimentation of waterways and estuaries.
If you're planning to undertake earthworks on your property, you may need to apply for resource consent so we can monitor the effect of the earthworks on the environment.
We can also provide guidance on the most appropriate protection measures to put in place before you start your earthworks.
You can call the council on (09) 301 0101 for information and advice on what to do before beginning your earthworks. You may also wish to check the relevant district plan and the unitary plan, or if you're considering larger-scale or more complex earthworks, the regional plan.
For minimum requirements for addressing land stability and earthworks, see the earthworks and geotechnical code of practice (PDF 1.5MB).
When sediment is carried into waterways and estuaries it reduces water quality, harms fish and other species that are sensitive to sediment, and smothers feeding areas and habitats for kai moana (seafood).
Sediment can also block streams, which increases potential flooding.
Eventually, the water carries the sediment downstream to the coast, causing sediment build-up in our harbours.
If you're undertaking an earthworks project, you should concentrate on controlling erosion.
You can do this by:
- minimising the area of disturbance
- performing earthworks in stages and stabilising exposed areas quickly after completing each stage
- retaining as much existing vegetation as possible, especially on steep slopes or areas close to watercourses, where a variety of measures are needed to adequately control erosion and transport of sediment, and where environments may be highly sensitive.
Other ways of controlling sediment are:
- working within the driest season (2 October to 31 April, often referred to as the 'earthworks season')
- ensuring that appropriate sediment retention devices (including perimeter controls to keep clean run-off out of your work area) are installed and operational before commencement
- coordinating with other services such as roading, gas, power, telephone and drainage to put erosion and sediment control measures in place.
Both the landowner and the contractor doing the earthworks are responsible for preventing soil erosion and stopping sediment entering waterways.
You should take appropriate measures to prevent soil loss and erosion regardless of the size of your earthworks, and even in cases where a resource consent is not required.
For more, see the following technical publications:
You can also find out more about land use consents on our types of resource consent page.