Earthworks for housing developments, clean filling, building roads, and undertaking forestry and farming activities can cause erosion and the release of sediment into waterways and the coast. Though sediment occurs through natural weathering and erosion, these activities can make it worse; causing a decline in both the quality and clarity of water in waterways and on the coast, and the habitats of plant and animal communities that depend on these environments. In particular, low-energy receiving environments such as the Porirua Harbour are adversely affected over time by the many activities that release sediment.
Under the Resource Management Act 1991, regional councils are responsible for controlling the use of land for the purpose of soil conservation, and where land use has impacts on water quality and water quantity. District and city councils are responsible for controlling the effects of the use and development of land, such as developing a section to build a house.
To avoid unnecessary duplication with city and district councils, GWRC only controls large scale soil disturbance (including roading and tracking) on steep land and areas of bulk earthworks greater than 0.3 hectares. These activities are controlled in Rule 1 and Rule 2 of the Regional Soil Plan and Rule 3 of the Regional Freshwater Plan. Any other activities involving earthworks are controlled by district rules in district plans.
