What to Do If Your Neighbour’s Stormwater Is Flooding Your Property in NSW

Water repeatedly entering your property from next door can be frustrating, but the first step is to establish where the water is coming from and why it is crossing the boundary.

Not every flow of rainwater from a higher property means that the neighbour's drainage is defective. On sloping land, some water may follow the natural contours of the land as natural overland flow.

The situation can be quite different when water has been redirected, concentrated or discharged towards your property by drainage works, downpipes, paved areas, retaining walls, landscaping or other changes to the adjoining property. NSW councils commonly distinguish between natural overland flow and runoff that has been altered or concentrated by development or drainage arrangements.

1. Work out where the water is actually coming from

Try to observe the property while it is raining rather than relying only on what is visible afterwards.

Look for where the water first crosses the boundary and whether it appears to come from:

• a downpipe or stormwater outlet
• a rainwater tank overflow
• a drainage pit
• a paved area or driveway
• a retaining wall
• recently changed landscaping
• fill or altered ground levels
• a concentrated flow path
• general surface runoff following the natural slope of the land

The distinction is important because the appropriate solution depends on the source.

2. Record what happens during rainfall

Photos taken several hours after rain may show a wet yard but not explain how the water arrived there.

Where possible, keep clear records showing:

• the boundary between the properties
• where water crosses the boundary
• the direction and approximate volume of flow
• any visible pipe, outlet or overflow
• ponding against your house, garage or retaining wall
• erosion or washed-out soil
• affected paving, landscaping or structures
• the date and rainfall event

Short videos taken while the water is actually flowing can be particularly useful when explaining the problem to a contractor, engineer, Council or the adjoining owner.

3. Check whether your own drainage is contributing to the problem

Before assuming that everything is coming from next door, check your own property.

A blocked pit, collapsed pipe, inadequate surface fall or restricted drainage path can cause incoming water to accumulate instead of continuing safely through the site.

Property owners are generally responsible for maintaining private stormwater components such as gutters, downpipes, pipes and pits serving their property.

Understanding both sides of the drainage issue can prevent money being spent on a solution that does not address the actual cause.

4. Speak to the neighbour if the source is identifiable

If the problem appears to come from a particular drainage outlet or recent work next door, raising the issue with the neighbour may be the simplest first step.

They may not realise that a tank overflow, downpipe, new retaining wall, paving or landscaping is affecting your property.

Where practical, show them photos or video of what happens during rain. Focusing on the observable drainage problem rather than starting with accusations usually makes it easier to identify a practical solution.

5. Do not simply redirect the water back

Creating a mound, wall, channel or drain solely to push the water back across the boundary can create another drainage problem.

Natural overland flow needs to be considered carefully, and NSW councils warn against diverting, redirecting or concentrating natural flows in a way that affects adjoining property.

Before changing ground levels or constructing drainage works near a boundary, obtain appropriate advice.

6. Get the drainage assessed

If the source is unclear or the problem is significant, a site inspection can help determine how water is moving across both the affected area and the surrounding land.

Depending on the circumstances, investigation may include:

• checking surface levels and falls
• tracing stormwater pipes
• inspecting downpipe connections
• checking pits and tank overflows
• assessing retaining wall drainage
• reviewing changes to paving or landscaping
• considering the natural overland flow path
• checking the approved stormwater arrangement where relevant

For more complex sites, input from a hydraulic, civil or structural engineer may be appropriate.

7. Contact your local Council where appropriate

Council involvement in private stormwater disputes varies according to the circumstances and the local government area.

Some NSW councils state that they may investigate where runoff from one property has been deliberately concentrated or altered, or where defective private drainage is affecting another property. They may have much more limited involvement where the issue is simply natural surface water following the existing contours of the land.

If you make a complaint, providing photographs, videos, dates, details of the suspected source and evidence of recurring impacts can make the issue easier to assess.

8. Do not ignore repeated water beside your house

Even if the water never enters the dwelling, repeated saturation beside the building can still warrant investigation.

The main concern may be the effect of persistent or uneven moisture on the supporting soil. Water can also contribute to erosion, damage landscaping, affect paving and retaining structures, or create ongoing damp conditions around the property.

If cracking, movement or other structural symptoms are developing, the drainage problem and the condition of the building should be assessed together.

How ARK Houses can help

ARK Houses can investigate residential drainage problems across the Central Coast, Newcastle and Hunter regions and help identify practical building and drainage solutions.

Where the problem involves surface levels, stormwater infrastructure, retaining walls or possible effects on the building, we can assess the site and coordinate appropriate specialist input where required.

The first objective is to determine where the water is coming from. Once the source and flow path are understood, an appropriate rectification strategy can be developed.

Contact us