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Drainlaying and Stormwater Terms You Need to Know

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Absorption Pit

An Absorption Pit is a shallow, basin-shaped depression typically filled with loose stone, gravel or crushed rock used to naturally absorb and filter stormwater runoff. Absorption Pits are often used in residential developments with impervious surfaces to capture and store stormwater runoff before allowing it to enter nearby water bodies.


New Zealand is known for its clean, fresh water and its use of aquifers makes it one of the leading countries in the world when it comes to sustainable water management.

An aquifer is an underground layer of water-bearing permeable rock, sediment, or soil. Aquifers provide a natural source of water for drinking, irrigation, industry, and other applications. Aquifers are also a valuable natural resource, providing economic, social, and environmental benefits.

The water contained within an aquifer is replenished by precipitation from rain and snow. Water moves into an aquifer from the surface either directly through infiltrated water, or indirectly through the flow of water in streams and rivers. The rate of recharge is dependent on the climatic conditions and type of ground cover. Aquifers can also receive water from other aquifers though a process known as inter-aquifer connectivity.

New Zealand has more than 500 aquifers which are spread throughout the country. These aquifers provide an important source of clean, safe drinking water as well as being an important component of the local ecosystem. Aquifers are an integral part of New Zealand’s water supply system as they provide a consistent, year-round supply of water and are capable of storing large volumes of water for future use.

In order to ensure that New Zealand’s aquifers are kept healthy and productive, several regulations have been put in place to protect this valuable resource. These regulations minimise the risks associated with aquifer use, such as over-extraction, contamination, and seawater intrusion. The New Zealand Government has also developed innovative ways to improve the sustainability of water management, such as the integration of non-traditional water sources, water reuse systems, and drought-proofing projects.

Axonometric Plan:

A three-dimensional view of a stormwater drainage system showing all the elements of the system in relation to one another.

Best Management Practices (BMPs):

Measures used to manage stormwater runoff to minimize its impact on the environment.

Bioretention System:

A Bioretention System is a constructed wetland that is specifically designed to capture, treat, and infiltrate stormwater runoff. Bioretention Systems use native plants and soils to naturally capture, retain, and filter stormwater runoff.

Catch Basin:

A Catch Basin is a type of stormwater drainage system that is designed to collect large amounts of runoff from roads, sidewalks, and other hard surfaces. Catch Basins are made from metal or concrete materials. They are normally located at the interface between areas of different elevations, like paving, to direct and capture low-flow runoff. These basins are commonly used in urban areas where stormwater runoff is generated in large quantities, and are often equipped with gratings, debris guards and/or filters to keep unwanted particles from entering the system.

Catchment area:

The geographical area from which rainwater drains into a particular stormwater system.


The area of land that the stormwater drainage system drains into.

Combined Sewer System:

A sewer system that carries both domestic sewage and stormwater runoff in the same pipes.

Commercial drainlaying:

The installation and maintenance of drainage systems for commercial properties. This includes the installation of sewerage, drainage, and stormwater systems, as well as repairs and maintenance. It also involves ensuring that the systems comply with all applicable regulations and standards.


A culvert is a waterway structure designed to carry water beneath a road, railway or other obstruction. Located all around the country, culverts in New Zealand play a key role in the management of stormwater. As the nation’s population and land usage continues to increase, the need for efficient stormwater management solutions is becoming increasingly important, and culverts are a key part of this process.

Culvert safely carrying water underneath a driveway

Culverts are used to control and redirect the flow of water in areas where it may otherwise become a hazard or impede development. During times of heavy rainfall, culverts act to protect low lying areas by preventing the water from flooding or damaging infrastructure. The use of culverts also helps to reduce the impact of flooding on nearby rivers, streams and other bodies of water.

Culverts are typically made from reinforced concrete, but may also be made from pre-cast concrete, steel or even old railway lines. Culverts differ in size, from small culverts designed to carry water from a single property to large culverts designed to carry an entire river.

Culverts are an important part of New Zealand’s infrastructure and can be found in urban, rural and recreational areas throughout the country. They are a necessity for managing stormwater in areas where there’s a risk of flooding or where development has the potential to impact on water flow.

As well as controlling water flow and helping to prevent flooding, culverts also provide easy access for vehicles and pedestrians to cross streams, rivers and other bodies of water. This can make it easier to access areas that might otherwise be inaccessible.

Culverts have been part of New Zealand’s infrastructure for many years and continue to provide a reliable and cost effective solution for managing stormwater and providing safe access to otherwise isolated areas. With the nation’s population growing ever-greater, the role of culverts in keeping the country’s water systems running efficiently will become ever more important.

Detention basin:

A type of stormwater management facility that temporarily holds stormwater runoff to allow sediment and pollutants to settle before release.

Detention Tank:

A holding tank used to temporarily store runoff during heavy rainfall to reduce flooding.

Diversion Structure:

A structure made of stone, concrete and other materials that guides water away from areas prone to flooding.

Downpipe or Downspout:

A Downspout is a type of stormwater draining system that is typically attached to the side of a building or structure. Downspouts collect and divert roof runoff away from the structure and into a drainage system or to a nearby water body. A downpipe typically consists of a solid pipe made of aluminium, galvanized steel, or PVC.


Describes the direction of flow from a higher elevation to a lower elevation, usually referring to a river or stream.

Drainage basin:

The area of land drained by a particular river or drainage system.

Drainage channel:

An artificial channel for carrying water.

Drainage pipe:

A pipe used for conveying stormwater runoff.

Drainage structure:

Any physical structure designed to manage stormwater runoff, including pipes, channels, basins, and other systems.

Drainage swale:

A shallow, vegetated channel used to convey stormwater runoff.

Drainage system:

A network of pipes, channels, and other structures for conveying stormwater runoff away from buildings, roads, and other areas. This is referred to as public drainage and is managed by the city or district council.


The decrease in water level in a storage tank during a rain event.

Filter Bed:

A Filter Bed is a layer of granular material such as sand, clay, or small gravel used to filter stormwater runoff. Filter beds are often used in constructed wetland systems or to treat stormwater prior to being discharged into a nearby water body.

French Drain:

A type of drainage system that uses open trenches filled with gravel and pipe to collect, store, and disperse stormwater.


Grates are metal or plastic grids that are placed over drainage inlets or channels to restrict trash and debris from entering stormwater systems.


A gully is an artificial channel which is used to convey stormwater runoff to a larger drainage system. They are commonly found along roadsides and can be constructed from concrete, brick, or other materials.


High-density polyethylene, a type of plastic material that is commonly used in stormwater drainage systems in New Zealand. It is available in several sizes and has a high resistance to corrosion.

Hydrologic cycle:

The natural cycle of water moving through the environment, including precipitation, infiltration, evaporation, and transpiration.

Infiltration or Infiltration Basin:

The process and system by which stormwater seeps  or is absorbed into the ground.

Infiltration Trench:

An infiltration trench is an underground structure that is used to allow stormwater runoff to infiltrate into the ground. The trench is typically lined with a porous material, such as gravel, and is used to reduce the potential for runoff to cause erosion or pollution downstream.

Landscape drains:

Landscape drainlaying is the process of installing landscape drainage systems to help control the movement of water away from areas of your section, such as gardens and driveways. These systems typically involve laying turfs, gravels, pipes, and other materials in order to control water runoff, preventing potential damage to structures or plants.


A manhole is a type of circular opening on the surface of the ground that is used to inspect, clean and maintain sewer lines. It can also be used to run electrical cables and other services into the drainage system. The structure is typically made out of metal or concrete, reinforced to withstand heavy traffic.

Non-Point Source (NPS) pollution:

Pollution that comes from multiple sources, including stormwater runoff.

Oil Grit Separator:

Oil Grit Separator is designed to separate suspended particles, including oil, silt, grease and floating material, from stormwater runoff. This separator uses the concept of a settling chamber, coalescing oil and solid particles with the use of flotation media.


The point where the stormwater leaves the stormwater system and enters a local water body such as a lake, river or ocean.


An Overflow is a stormwater drainage system component that is used to safely and effectively dispose of excess runoff during periods of heavy precipitation of runoff. Overflows are typically directed to nearby water bodies.


The process by which water moves through soil or other porous material.

Public drainage:

The network of underground pipes and systems used to collect and remove wastewater from the local area for treatment and disposal. This infrastructure is usually managed by a local or district council. Public drainage systems typically include sewers, stormwater collection and treatment plants, and other related elements such as pumps and valves.

Rain Garden:

A Rain Garden is a type of stormwater treatment system that utilizes native plants and soils to naturally capture, treat, and filter stormwater runoff. Rain gardens are often used to treat stormwater from impervious surfaces in residential developments.

Rainwater Harvesting System:

A system designed to capture, collect, and store rainwater for use in homes or other buildings. It typically consists of a rainwater tank and a filter to collect pollutants from the water before it is used.

Retention basin:

A type of stormwater management facility that holds stormwater runoff to allow it to be infiltrated into the ground.

Retention Pond:

A retention pond is an underground structure which is designed to slow the flow of stormwater runoff from roads and paths. They are usually lined with an impermeable material such as clay, and are often planted with vegetation, grass, and trees in order to provide an aesthetic benefit.

Retention Tank:

A large tank used to store stormwater runoff, typically built as part of a larger stormwater management system.

Rigid Piping:

Any type of pipe that is rigid and cannot easily be bent or twisted. It is often used in underground drainage systems due to its strength and durability.

Runoff Control:

A variety of methods used to reduce the amount of runoff entering a drainage system.


Water that flows over surfaces such as roads or rooftops.

Sediment control:

Measures taken to prevent or reduce the amount of sediment carried by stormwater runoff.

Sedimentation Basin:

A type of detention or retention pond designed specifically to capture sediment before it reaches our water bodies.

Settling Basin:

A Settling Basin is a large concrete or earthen structure designed to store and capture stormwater runoff for a period of time, allowing for dirt and debris to settle out of the water. Settling Basins are often used in conjunction with other stormwater treatment systems to improve water quality.


Stenosept is a kind of precast concrete trench that is used to collect, transport and divert stormwater runoff. The structure is normally constructed in long, narrow lengths with a protective layer of geotextile fabric coating the outside to keep soil and other debris from entering the system.

Storm Drains:

Storm Drains are constructed trenches dug into the soil that collect and direct excess water away from the developed area. Storm drains are typically constructed using concrete, metal or plastic components. They are connected to upstream surface drains and inlets to direct runoff away from structures, ensuring the effective management of water.

Storm Tank:

A type of collection tank used for storing large volumes of stormwater. It is fully sealed to prevent water loss through evaporation, and is designed to collect and direct water to other outlets for safe and efficient drainage.

Stormwater Chamber:

A stormwater chamber is an underground structure that is used to manage stormwater runoff from roads and paths. They come in various sizes and can usually be fitted with a gravel filter for removing dirt and debris.

Stormwater Detention Ponds:

Stormwater detention ponds are basins designed to capture, store and slowly release runoff generated by rain and other precipitation onto streets, yards and other impervious surfaces. These systems limit the rate at which runoff is released and help to mitigate flooding and erosion.

Stormwater discharge:

The release of stormwater runoff into a body of water.

Stormwater Drainage System:

A system of channels, pipes, and other structures that transport stormwater runoff away from buildings and roads and into nearby creeks, rivers, and other water bodies.

Stormwater Filters:

Stormwater Filters are filter units that are designed to capture and filter stormwater runoff prior to discharge into a nearby water body. Stormwater Filters are typically used to remove sediment, oil, and other contaminants from stormwater runoff.

Stormwater harvesting:

The collection and storage of stormwater runoff for reuse.

Stormwater management:

The planning, design, construction, and maintenance of stormwater drainage systems.

Stormwater Outlet:

A structure that allows accumulated stormwater runoff to enter a body of water or underground drainage pipes.

Stormwater Pipe:

A Stormwater Pipe is a type of pipe that is specifically designed to convey stormwater runoff from one point to another. Stormwater pipes are typically six inches in diameter and can be made of concrete, plastic, or metal.

Stormwater quality control:

Measures taken to prevent or reduce the amount of pollutants carried by stormwater runoff.

Stormwater runoff:

Water from precipitation (rain, snow) that flows over the ground surface.

Stormwater Tank:

A stormwater tank is an underground structure which is used to store stormwater runoff from roads, paths, and other sources. They are commonly made from a variety of materials such as concrete, steel, or plastic and can be fitted with a pump to help remove the stored water.

Submersible Pump:

A type of pump used to move stormwater from one location to another, typically between storage basins and outfalls.

Subsurface Drainage System:

A type of drainage system that collects, stores, and routes stormwater runoff below the surface of the ground.


A drainage area below the primary catchment area, usually referred to as a sub-catchment.


A pit or lower point in a stormwater system, usually housing a pump, used to collect and move water to another location.

Surface Flow:

The flow of stormwater over land surfaces.

Surface Inlet:

A type of inlet designed to collect and convey surface water, such as stormwater runoff, to a drainage system. There are several types available, such as grated inlets, curbed inlets, and filter inlets.


A swale is an open channel which is used to convey stormwater runoff from roads, paths, and other drainage systems. They are commonly planted with grass, and help to slow the water’s flow and reduce potential erosion.

Trunk Sewer:

A large main sewer line that receives water from smaller tributaries.

Underground Storage System:

A system of pipes, trenches, and other components that collect, store, and disperse stormwater runoff below the surface of the ground.

Urban Runoff:

Stormwater that is produced in an urban area and is discharged into a stormwater system.

Wastewater Treatment Plant:

A facility used to filter and process wastewater before it is discharged into a local body of water.

Water quality:

The physical, chemical, and biological characteristics of water that determine its suitability for a particular use.


An area of land that is deliberately flooded with stormwater runoff, typically to improve water quality or provide habitat for wildlife.


A type of ecosystem that includes marshes, swamps and bogs, used to store and filter stormwater runoff. Corrugated steel: A type of stormwater drainage material used in New Zealand which is produced from corrugated steel sheets. It is strong, durable, and easy to install and is commonly used for underground or overground drainage systems.


Fox Drainage provide residential and commercial drain laying throughout Auckland. Let us know how we can help.

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