Glossary Print




Annual Exceedance Probability. The probability of exceeding a given storm discharge or flood level within a period of one year. For example, a 1% AEP floodplain is the area that would be inundated in a storm event of a scale that has a 1 per cent or greater probability of occurring in one year.


Auckland Transport. A council-controlled organisation responsible for transport, including some stormwater functions in the road corridor.


Auckland Transport Code of Practice.

Auckland Design Manual

A best practice guide for designing the built environment. Available online at

Best Practicable Option

In relation to a discharge of a contaminant or an emission of noise, means the best method for preventing or minimising the adverse effects on the environment having regard, among other things, to:

• The nature of the discharge or emission and the sensitivity of the receiving environment to adverse effects

• The financial implications, and the effects on the environment, of that option when compared with other options and

• The current state of technical knowledge and the likelihood that the option can be successfully applied.


Corridor Access Request. An authorisation for working in the road corridor, administered by Auckland Transport.


The area draining to a site. It always relates to a particular location and may include the catchments of tributary streams as well as the main stream.


Code Compliance Certificate. A certificate issued by the council at the end of a building project to demonstrate satisfaction that the completed building work complies with the original building consent.


Closed Circuit Television. Used to inspect pipelines in order to determine the interior condition of the pipe.

Coastal Marine Area

Generally the area below mean high water springs.

Community Services

The Auckland Council department which is the asset owner for public parks and reserve land.


Code of Practice. In legacy councils in the region these were also known as: 'Connection Standards’, ‘Quality Standards’, ‘Design Standards’ or ‘Development Code’.


Any conduit that transfers the flows of a watercourse or waterway across a road or embankment.

Design Flows

The flows selected as a basis for the design of works in the system.

Design Storm

The rainfall calculated from historical records that can be expected for a specific return period and duration.

Engineering Approval

Engineering Approval is required for works that are to be vested in the council’s ownership. This includes public stormwater, wastewater, water supply, roading and park assets. Engineering Approval may also be required in other circumstances, such as a condition of an underlying resource or building consent.


The area of land that is inundated by water during a specific flood event. In the SWCoP the 1% AEP flood event is used.

Flood-Sensitive Area

The area bordering the 1% AEP floodplain which is within 500mm in elevation of the predicted 100 year flood level.


The inadvertent loss of drilling fluid from the borehole annulus to the surrounding soil as a result of excess downhole fluid pressure. Also known as hydrofracture.


Additional clearance above estimated flood level to allow for uncertainties in flood level estimation, wave action and localised water level variations.


Guideline Document. An Auckland Council publication which provides technical and/or design guidance.


The invert level is the base interior level of a pipe, or culvert.


Local Government Acts 1974 and 2002.

Minor Pipelines

Pipes with an internal diameter of less than 200mm that are not on the main pipe alignment.


Maximum Probable Development. Design case for consideration of future flows allowing for development within a catchment that takes into account the maximum impervious surface limits of the current zone or, if the land is zoned Future Urban in the Proposed Auckland Unitary Plan, the probable level of development arising from zone changes.


Network Discharge Consent. A consent that authorises the diversion and discharge of stormwater, including associated contaminants, from existing and potential future public stormwater networks within urban areas and rural and coastal settlements.

Non-Access Chamber

An inspection chamber which does not allow a person to enter. Refer to Appendix B, drawing SW06 for a typical detail.

Overland Flow Path

The route taken by stormwater when flowing over land.


Proposed Auckland Unitary Plan. Notified 30 September 2013, the PAUP gives provisions for activities and development in the Auckland region.

Peak Flow

The maximum flow reached in a stormwater system during any storm (or at any time in other reticulation).

Primary System

The pipes, streams, open watercourses and other elements of built and natural drainage infrastructure that carry the flow of stormwater within the catchment during non-extreme storm events. They generally should have capacity for the 10% AEP flow.

Private Stormwater

Any component of the stormwater network that drains water from premises on private land to a receiving environment or up to the point of service connection with the public stormwater network and includes pipes, gutters, downpipes, catchpits, swales, subsoil drains, stormwater treatment devices, rain water tanks and any stormwater management device or redundant stormwater system.

Public Stormwater

Public stormwater network includes:

1. Any stormwater pipe, drain, land drainage work or treatment facility, vested in or under the control of the council; and

2. Any stormwater drain, drain, land drainage work or treatment facility declared by the council to be a public drain under Section 462 of the Local Government Act 1974.


The stormwater assets of other public entities such as Auckland Transport, Auckland Council Community Services and NZTA are not considered “public” in the context of this document. They may be owned by a public entity, but are not “public” assets that can be connected to.


Resource Management Act 1991. New Zealand's main piece of legislation that sets out how we should manage our environment.


The portion of rainfall which runs off the land and into the drainage system and overland flow path.

Runoff Coefficient

The proportion of rainfall landing on a given area which contributes to runoff.

Secondary Flow Path

The route taken by stormwater runoff when the primary system capacity has been exceeded or is blocked.


Disposal of stormwater into the ground by way of specifically designed pits, trenches or bores.


The highest point of the internal surface of a pipe or culvert at any cross section. Sometimes called the obvert.

Stormwater Device

A device or facility used to reduce stormwater runoff volume, flow and/or contaminant loads prior to discharge. Examples are rain gardens, pervious paving and tree pits.


Stormwater. Rainfall runoff from land, including constructed impervious areas such as roads, pavement, roofs and urban areas which may contain dissolved or entrained contaminants, and which is diverted and discharged to land and water.


Code of Practice for Land Development and Subdivision Chapter 4 – Stormwater.

Time of Concentration

The time it takes for water to arrive from the top of the catchment to a location downstream.


Technical Publication. A former Auckland Regional Council technical document.


Technical Report. An Auckland Council technical report.

Vulnerable Activities

As defined in the Proposed Auckland Unitary Plan (PAUP).

Watercare CoP

The Water and Wastewater Code of Practice for Land Development and Subdivision.


Water Sensitive Design. As defined in the Proposed Auckland Unitary Plan (PAUP).

Zone of Influence

See drawing SW22 in Appendix B. ​​

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