Stormwater Drainage on Private Properties


In an emergency

For emergency help in flood events, contact the State Emergency Service (SES) on 132 500.

Stormwater issues

As a result of Hornsby Shire’s climate and topography, flooding and nuisance issues from stormwater is a common problem for many residents, especially if they believe the water is coming from another property. Council understands that this can cause disputes between neighbours, and Council does its best to ensure that proper action is taken if required and/or legislatively possible.

Stormwater is rainwater that runs off surfaces such as lawns, roads, roofs, car park and natural ground surfaces. Stormwater that is unable to enter the underground drainage system will find its natural way to the nearest watercourse via overland flow paths. These overland flow paths are typically natural depressions (that occur through private property), open channels, roadways, and public reserves.

Property owners have a range of responsibilities, which if carried out correctly, will minimise the threat of stormwater damage in the event of heavy rain:

  • You must maintain your roof water drainage, stormwater pipes, gutters, downpipes, stormwater inlet pits and any other components of your approved drainage system on your property in good condition and in compliance with any Council requirements.
  • You are required to accept natural overflow and from adjoining properties or public land and must not divert, redirect, or concentrate the flow from its natural path on to neighbouring properties.
  • It is important to note that a downstream property owner cannot erect any type of barrier by way of large walls or closed fencing that interferes with the path of stormwater – if you are downstream, you must accept the ‘natural’ run‐off on to your property.
  • Ensuring that all buildings (including sheds) have an adequate storm water drainage system connected to the legal point of discharge (e.g. connected to the kerb and gutter or inter‐allotment drainage system).
  • When constructing hardstand areas, you must control stormwater in order to prevent it from flowing on to adjacent property. It is preferable to minimise the area of water‐resistant surfaces such as concrete or paved areas and driveways.
  • If there is an easement on your property it must be maintained and kept clear of debris to allow the natural flow of the stormwater.

Property owners generally need to ensure that roof water and stormwater is drained to one of the following to comply with AS/NZS 3500.3:2003 Plumbing and Drainage Part 3: Stormwater Drainage.

  • Council street kerb and gutter.
  • An inter‐allotment drainage system,
  • Approved on-site disposal system, or
  • Council controlled drainage easement or draining reserve.

Council Officers investigate and may take action on stormwater drainage complaints only where it relates to the flow of surface water from one property across the common land boundary onto another property, and where all of the following criteria has been met:

  • Sufficient evidence being produced that substantiates the surface water has caused or is likely to cause physical damage to land or building on the other land.
  • surface water has been directed to and/or concentrated in a particular area by a man‐made structure or drain.
  • surface water is the result of defective roof drainage from a dwelling or an outbuilding.

Disputes between neighbours often arise where residents believe that drainage or stormwater arising from a neighbouring property is causing or is likely to cause damage including flooding.

In the first instance, neighbours are strongly encouraged to talk with one another to address any stormwater concerns. Talking with neighbours often results in a more amicable, timely and cost-effective outcome.

Where concerns are unable to be resolved directly between neighbours, residents are encouraged to formally manage discussions through the Community Justice Centre. The centre offers free advice and mediation services and can be contacted on 1800 990 777.

Council Officers have the discretion to take no action or are unable to take action in the following circumstances where:

  • the surface water is natural run‐off from the property or properties above due to the topography and is not redirected in any manner.
  • in some instances where surface water is flowing down or across existing hard surface areas such as driveways, tennis courts, concrete slabs, or paved areas.
  • the location of a dwelling or outbuilding impacts on surface run‐off.
  • surface water run‐off occurs only in periods of exceptionally heavy rain.
  • surface water is a result of overflows from stormwater absorption pits where contours of land and lack of access prevent direct connection of a building’s roof water to the council’s stormwater drainage system.
  • the run‐off from new development work that is the subject of a development consent or complying development and has been constructed in accordance with that consent.
  • the drainage problem involves discharges from defective or blocked private inter‐allotment drainage easement infrastructure e.g., pipes and drainage pits.

Overland flow is the path down the slope following the contours of the land and occurs before any excavation, development or building is created. An upstream property owner cannot be held liable merely because surface water flows naturally from their land on to the lower land of a neighbour.

If you are a resident living on a sloping site, you should be aware that natural surface water run‐off flows down the slope following the contours of the block.

Unless the cause of the surface water meets the criteria above, you carry the responsibility to install surface water controls. Any diversion of surface water must be carried out in a way that does not have a detrimental impact on any other properties further down the slope.

Council is unlikely to investigate stormwater complaints involving the natural flow of stormwater from one property to another.

Complaints about buildings under construction that are subject to a current building approval should, in the first instance, be referred to the responsible Principal Certifier (PC) or the Builder.

The details for the Principal Certifier and Builder should be visible on the building sign on the front of the property.

The individual builder remains responsible for all stormwater installations permitted under the development consent whilst the building is under construction. In the event of a complaint, the PC has enforcement powers and must take appropriate action under relevant legislation.

Seepage water is the responsibility of individual property owners. Where sloping blocks have been excavated to obtain a flat yard or building site, seepage drains should be constructed to redirect water to a stormwater drainage system.

You should liaise with neighbours to address any problems. If possible, drainage easements can be created to direct water to a council stormwater drainage system.

A drainage easement is a legal encumbrance on the title of a property to provide Council with the authority to carry out whatever works are required on drainage infrastructure within the easement. The infrastructure can include open drainage channels, below ground pipe systems and grated inlets that are designed to accept allotment and roof water together with larger upstream catchment stormwater flows.

Generally, no structures or improvements (such as dwellings, buildings and landscaping treatments including earthworks, retaining walls and fill) are permitted within the easement boundaries.

The property owner is responsible for the maintenance of an easement on private property. Council is not responsible for vegetation maintenance, including the clearing of weeds and trees or any other maintenance of overgrown vegetation, to watercourse or easements located within private property.

How to report a stormwater drainage issue

When reporting a stormwater drainage issue on private land, please include the following information:

  • describe what is happening.
  • when did it occur and on how many past occasions.
  • have you contacted Council about this issue previously.
  • what is the source on the neighbouring land that is causing the problem.
  • describe how your land and/or building are being damaged. (if possible include a written report from a suitably qualified person stating the land or building is likely to or is being damaged).
  • have you obtained professional advice as to the source of the stormwater issue.
  • have you liaised with your neighbour to address this matter.
  • have you sought advice or initiated mediation with your neighbour through the Community Justice Centre (details below).
  • take photos of the stormwater problem as it is occurring.

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