Stormwater management

Land transport activities can adversely affect water quantity and quality through discharges by:

• affecting natural waterways and drainage patterns
• increasing local stream flood flows
• transferring pollutants from road surfaces
• erosion and sediment from construction and maintenance activities entering watercourses.

This can have significant impacts on waterways, resulting in a deterioration and destruction of flora and fauna biodiversity, aesthetic features, structures and water quality.

Land transport systems also add to local and wider flooding issues, which we need to manage through drainage systems (piping, culverts, swale, ponds, wetlands, table drains, etc).

We need to proactively manage our activities to ensure we minimise adverse effects on the receiving environment.

We do this through our standards and guidance, which ensure careful planning and design to avoid, remedy or mitigate effects of excess flooding, erosion, sediment runoff and contaminated stormwater runoff. These all align with our responsibilities set through regional councils.

Our policy

Our policy on water resources and erosion and sediment control can be found in:

• Environmental plan: improving environmental sustainability and public health in New Zealand

Standards and specifications 

• Stormwater treatment standard for state highway infrastructure
• P46 NZ Transport Agency state highway stormwater specification
• P47 Specification for environmental, social and cultural management during construction
• P39 Standard specification for highway landscape treatments
• New Zealand ground investigation specification(external link)
• National environmental standards for freshwater(external link)

Guidance 

• Erosion and sediment control guidelines for state highway infrastructure: construction stormwater management
• Fish passage guidance for state highways*
• F1 Earthworks construction
• F2 Pipe subsoil drain construction
• Landscape guidelines
• Guide to road design part 5A: drainage: road surface, networks, basins and subsurface (Austroads)(external link)

* Note: our Fish passage guidance for state highways is currently out of date. We are in the process of updating it, along with a new policy and specification. In the meantime, refer to and follow:

• New Zealand fish passage guidelines for structures up to 4 metres(external link)
• National environmental standards for freshwater(external link)
• National policy statement for freshwater management 2020(external link)
• Freshwater Fisheries Regulations 1983(external link)

Resources and tools

• Erosion and sediment control inspection forms and pre-construction meeting checklist
• Erosion and sediment control guide for land disturbing activities in the Auckland region(external link)
• Biodiversity

Research

• Research report 131: Environmental management for roading contractors II: provisional guidelines for erosion and sediment management during road works (1991)

Further information

For further information contact environment@nzta.govt.nz