Stormwater network

Management of the stormwater network

Roads ACT is responsible for managing, monitoring and maintaining the physical condition of the municipal stormwater network, for setting standards for the construction of new stormwater assets and for ensuring the safe and effective functioning of the stormwater network as a whole.

As of 2007 the stormwater asset for which the stormwater unit is responsible is estimated to be composed of:

• 6,260 kilometres of pipes
• 62,376 sumps
• 27,697 manholes
• 56 kilometres of lined channels
• 104 kilometres of unlined channels
• 157 kilometres of grassed floodways
• 2 dams
• 12 weirs
• 94 gross pollutant traps
• 15 retarding basins

Scrivener dam is a National Capital Authority asset.

The average stormwater pipe asset is up to 50 to 70 years of age. The various components of the system are expected to have a functioning life of 75 to 100 years. Roads ACT is currently in the process of collecting and collating information about the extent and condition of the stormwater network. This information is contained in the Integrated Asset Management System for Transport Canberra and City Services (TCCS). The system contains condition and maintenance history information for the entire stormwater network. This information will become increasingly important as the stormwater asset nears the end of its design life and options for replacement are considered.

The current Asset Management Plan for Roads ACT details how we plan to maintain the stormwater network.

Standards change over time, but through implementation of a progressive program, the Territory will enhance the network and address problem areas by constructing infrastructure to current standards. Ranging from major works to localised issues, rolling upgrades are being planned around Canberra to manage water movements more effectively. Read more about the current infrastructure upgrades underway.

Agencies involved in the design and maintenance of the stormwater network

Several other agencies within and external to TCCS are responsible for the design and maintenance of various aspects of the stormwater system. The Environment, Planning and Sustainable Development Directorate is responsible for the master planning and development of the new stormwater network at the sub division level. Roads ACT is responsible for planning and maintaining roads and kerbs as part of the stormwater system. City Presentation is responsible for the maintenance of grassed floodways, urban lakes, water bodies and other 'natural' physical components of the stormwater network.

Private land developers are responsible for constructing the stormwater network within suburbs according to standards set by Roads ACT and detailed in the Design standards for urban infrastructure - Section 1 - Stormwater. (PDF 5.5MB)

EPSDD and several community groups work with Roads ACT to manage the natural environment and control the amount of pollution entering the stormwater network.

Stormwater quality

Urban run off generated in Canberra ultimately ends up in the Murrumbidgee River. The Canberra community has expressed concern that stormwater flowing into the Murrumbidgee should not degrade the general water quality, the aquatic environment or the recreational opportunities afforded by the river. These values are reflected in the actions of several local volunteer catchment groups, the actions and directives of the Environmental Protection Authority (EPA), and in the growing general interest in water management Australia wide.

The possibilities for stormwater pollution are many and varied. As stormwater flows across the urban landscape it collects litter, organic matter, particles of soil, and oil and other pollutants from roadways. In waterways these contaminants increase the turbidity, nutrient and bacteria loading of water, and they physically congest waterways. All of this can lead to a very unhealthy waterway in which the ecological balance of aquatic flora and fauna is altered and the utilisation of water for human use becomes increasingly limited.

The Environment website has considerable information on what residents of the ACT can do to reduce contaminants in stormwater. For more information on water pollution in the ACT contact EPSDD on 13 22 81.

Increasingly the community of the ACT is seeking to have input into the management, design and function of urban waterways. The Sullivans Catchment Group, the Ginninderra Creek Catchment Group and the Southern ACT Catchment Group are but three examples. These groups are aiming to restore creek lines, tributaries and catchments to a more natural state, with the inclusion of wetlands and the reintroduction of native fauna. This is intended to enhance the appearance and the functioning of the catchments. Roads ACT has been participating with various catchment groups in the ACT.

Design of the stormwater network

The stormwater system functions to mitigate flooding in urban areas. In the process it has a number of systems in place to reduce the amount of pollution that enters the Murrumbidgee River.

To maintain water quality and aquatic diversity the ACT Stormwater Management Strategy has been developed. Significant aspects of the strategy are listed below. The strategy:

• has legislation in place that enforces erosion and sediment control at the source of development;
• promotes the use of natural creeks, waterways, wetlands, water quality control ponds and urban lakes to afford increased opportunities for filtering and settling of sediment, and
• requires the installation of major and minor gross pollutant traps for the removal of coarse sediment and litter from stormwater runoff.

The ACT stormwater network consists of minor and major drainage systems. The minor (piped) system is designed to mitigate nuisance flooding, the major system is the continuous overland flow path or floodway system that is designed to accommodate less frequent large flood events and overflows from the minor system.

The minor system consists of the arrangement of kerbs, gutters, roadside channels, swales, sumps and underground pipelines designed to fully contain and convey runoff generated during a typical storm event.

The major drainage system consists of an arrangement of pavements, roadway reserves, floodways, retarding basins, and major cut off drains etc. that are planned to convey a design flood of 100 Years Average Recurrence Interval (ARI).

Stormwater floodway signage

Roads ACT provide floodway advisory signage to discourage people from congregating near stormwater drains and floodways. For more information visit the Policy for Floodway Advisory Signage.

Street drainage

Urban streets are provided with a system of pipes and kerbside sumps to drain runoff from small frequent storm events. The number and spacing of kerbside sumps reduces the amount of runoff flowing on the road pavement to provide safety for pedestrians and motor vehicles. The street drainage system also provides for drainage from adjacent properties. Runoff from streets and adjacent properties is drained via the municipal pipe system to the major drainage network of engineered waterways.

Streets also act as overland flow paths whenever flows exceed the capacity of the street drainage system or whenever kerbside sumps or sump entrances become blocked with debris. The street drainage system is designed to keep the amount of overland flow from storms up to and including 100 years ARI within certain limits for public safety and vehicle stability. Streets thereby provide a safe and effective means of conveying overland flows to the major drainage system.

Retarding basins

Retarding basins are a component of the major stormwater system. The purpose of a retarding basin is to reduce peak flows within the major drainage system downstream of the basin by temporarily storing runoff and releasing it at a reduced rate. Retarding basins are particularly useful for reducing the amount of flow from a new development so that the capacity of a downstream waterway is not exceeded. They are also effective in reducing the size required for engineered waterways in new urban areas and reducing flooding problems in existing urban areas.

Wherever possible, retarding basins are planned to accommodate additional uses other than runoff flow control. Sporting fields are often incorporated into the layout of retarding basins to provide multi-purpose usage during periods of dry weather. Typical examples are Southwell Park, Griffith Park, Narrabundah and Duffy Ovals.

Gross pollutant traps (GPTs)

Gross pollutant trap Amaroo, with wetlands behind.

In accordance with the ACT Stormwater Management Strategy, GPTs act as the first water pollution control point in the stormwater network. They prevent the flow of coarse sediment, trash and debris into engineered waterways, water quality control ponds, and urban lakes. GPTs are designed to remove a maximum of 70% of coarse sediments in flows up to and including 1 year ARI. This maintains the appearance of these waterways and water bodies, assists with the maintenance of water quality, and ensures the health of downstream flora and fauna.

GPTs are classified as major or minor depending on their size and to what part of the stormwater network they are connected. Minor GPTs are below-ground and are located within or at the downstream end of a pipe system. Major GPTs are above-ground and are generally located within or at the downstream end of an engineered waterway. GPTs are composed of a concrete lined 'wet basin' with a trash rack on the downstream side to intercept floating trash and debris. The concrete construction of the wet basin allows for easy trash removal and dredging of settled sediments.

Water quality control ponds and wetlands

The main function of water quality control ponds and wetlands is to hold water for a sufficient amount of time for various biological and physical processes to act to improve water quality.

A significant factor in the ability of water quality control ponds to improve water quality is the filtering action of macrophytes. Macrophytes are large aquatic reeds, which along with their associated microbial root mats, physically filter the water and absorb nutrients and other pollutants from the water. Significantly, the reeds also trap oil.

The stillness of pond waters also permits time for fine particles to fall out of the water and to settle on the bottom of the pond. Decomposition and grazing of organic matter by microbes, insects, fish and birds also occurs in this zone. Under the right conditions periodic algal growth will occur in ponds, this will trap dissolved excess nutrients and allow them to enter the food chain or settle on the bottom of the pond.

Urban lakes

Urban lakes in the ACT are intended to serve many functions. These include:

• enhancing the urban landscape;
• increasing the value of land in the vicinity of lakes;
• providing opportunities for nature conservation;
• supplying water for parkland watering systems, and
• providing recreational opportunities.

Urban lakes also significantly provide additional opportunities for the biological and physical treatment of water and they can act as large retardation basins during storm events.

Murrumbidgee River

Stormwater runoff in the ACT enters the Murrumbidgee River and then flows into the Murray River. Over the last 25 years it has been increasingly noted that water quality, and environmental issues generally, are best considered on a broad scale. In accordance with this, options for the maintenance of water quality are well considered within the framework of Total Catchment Management. Total Catchment Management highlights the fact that the pollution of urban stormwater needs to be controlled and reduced if we want to have a healthy river system. Within the ACT there are many things that each of us can do to reduce the pollutant load in urban stormwater.

Urban fringe

A special type of engineered waterway, called a cut-off drain, is provided along the urban fringe to protect properties from surface runoff from higher undeveloped hill slopes. Cut-off drains are typically grassed or earthen open channels designed to intercept surface runoff from storms up to and including 100 years ARI and channel it to the major drainage system.

If you live along the urban fringe you should familiarise yourself with the location of the cut-off drain that is protecting your property from stormwater runoff . More information about cut-off drains is located in the Your responsibilities section of this website.

Engineered waterways

As previously mentioned, the stormwater system is composed of major and minor stormwater systems. The main element of the major system is the engineered waterways, which can take the form of a natural waterway, a grassed floodway, or a lined channel. The primary function of engineered waterways is to collect and safely convey runoff from storm events up to and including the 100 year ARI. During small storm events, engineered waterways receive runoff from the minor drainage system only. In large storm events, excess runoff that cannot be carried by the minor drainage system, will flow overland via the street network to the engineered waterway system.

Until the mid 1970s, the major drainage system was constructed using concrete lined channels. Water levels in concrete lined channels can rise very quickly without much warning and flows can reach velocities up to 12 metres per second (approximately 40 kph) which can be extremely hazardous to the public. The major drainage system is now constructed using grassed floodways and natural waterways to provide far greater safety for the public. The average flow velocity is limited to 2 metres per second to prevent erosion and the floodway sides are limited to a maximum slope of 1(vertical) to 6 (horizontal) so the grass can be maintained.

Protecting your property from flooding

For advice on how to keep your property from flooding, please visit protecting your property from flooding.
To see if your property is at risk of riverine flooding during a major storm event (a 1% EAP, formerly known as a 1 in 100 year event), please visit Riverina Flood Maps.

Ensure that cut off drains behind your house are clear of obstructions

Cut off drains filled with debris, are a potential flood and pollution hazard. Please ensure that any cutoff drain behind your house is not filled with lawn clippings, tree pruning's or household rubbish.

Sump conversions

For information on the procedure for the conversion of standard stormwater sump cover to trafficable cover see sump conversions.

Construction in the vicinity of stormwater easements

Major permanent structures are not permitted within stormwater easements. Some small structures must meet the specifications and restrictions detailed in Summary of requirements: Construction in the vicinity of stormwater easements (PDF 255KB).

Prior to any construction you are required to obtain approval from Transport Canberra and City Services (TCCS) for developments under the 'Exempt' or 'Code' categories and from ACTPLA for developments under 'Merit' and 'Impact Assessment' categories. For approval from TCCS, please contact the Senior Manager of Asset Acceptance (TCCS) through Access Canberra on 13 22 81. Approval from Planning is obtained through the lodgement of a Development Application.

Do ACT Government representatives or contractors need to access my property for stormwater network maintenance?

Access to residential properties is sometimes required to perform essential maintenance. For example, properties in newer suburbs connect to the stormwater network at a tie point. Stormwater ties connect via pipe to a stormwater main or to the kerb of a street which can be on or nearby residential properties.

Does the ACT Government hire contractors for stormwater maintenance?

Yes. You might have received a notice from Flexible Australia, an ACT Government contractor, regarding attending your property for maintenance. TCCS stormwater maintenance officers will complete an initial inspection and determine the maintenance required. They will then issue work orders to the maintenance contractor for actioning. Once Flexible Australia has the work allocated to them, they will schedule the work and use ACT Government marked letters for letter box drops.

How will I know if access to my property is required?

You might have received a Notice of Stormwater Maintenance. This means an ACT Government employee or authorised maintenance contractor, such as Flexible Australia, is reaching out to investigate or provide an update about stormwater maintenance nearby or on your property. Your Notice of Stormwater Maintenance will inform you whether or not access to your property is required.

What type of maintenance works are required to keep a functioning and healthy stormwater network?

The type of work required can include:

• CCTV inspections
• stormwater tie replacement requiring digging or trenching
• stormwater lid and tops replacement
• underground stormwater mains or sump repair
• underground stormwater mains or sump replacement, which can include disruptive civil work, large machinery and traffic management.

Who can I contact regarding stormwater maintenance on my property?

If you need to get in touch, please call Access Canberra on 13 22 81 and ask for an officer from the Roads Maintenance division within Transport Canberra and City Services. Please be sure to include your address and a description of the issue.

Find the location of your stormwater tie via the plumbing tie search.