Guide
Overland flow paths: what they mean for an Auckland property
A flow path across a section is one of the findings buyers most often misread — as flooding, which it is not, or as nothing, which it also is not. It is a constraint on where and how you can build, and it is worth understanding before it shapes a decision you have already made.
Part of How to research a property before buying in New Zealand.
What an overland flow path actually is
When rain falls faster than the ground and the pipes can take it, the surplus runs across the surface and finds the low ground. An overland flow path is the modelled route it takes. Auckland Council derives these paths from LiDAR — an aerial elevation survey accurate enough to see the shape of a driveway — and then traces where water would run downhill across that surface.
Two consequences follow from how they are made. The first is that a flow path is a statement about the shape of the land, not about a river or the sea: it can cross a section that is nowhere near either. The second is that it is modelled from elevation rather than measured from an event. A mapped path is not a record that water has run there, and an unmapped section is not a record that it has not.
A flow path is not a flood plain
A flood plain is a modelled extent of standing water — how far an inundation reaches in a storm of a given rarity. A flow path is a line describing where moving water goes on its way somewhere else. They are produced differently, they mean different things, and a property can have one without the other.
They also matter at different moments. A flood plain finding tends to shape insurance and lending conversations. A flow path finding tends to shape what you can build, and where.
What a flow path across a property affects
Auckland Council uses mapped flow paths when it sets building setbacks and when it assesses consent applications. That is the practical weight of the finding: it is a design and consenting constraint on the land, and it applies whether or not the current house has ever had water through it.
Where it usually shows up
- Building or extending. A flow path crossing a proposed footprint changes what can be consented, and can change the design, the levels, or the position of the building.
- Earthworks, regrading and retaining. Work that alters the surface alters where the water goes, which is exactly what the mapping is about.
- Driveways, garages and hardstand. Adding impervious surface across a flow path is a stormwater question, and a garage floor sitting in one is a design problem worth catching early.
- Fences, sheds and landscaping. Blocking a flow path can move water onto a neighbour, which is a consenting matter and can be a legal one.
- Existing structures. Where a flow path crosses something already built, it is worth understanding what was consented and when — a question the property file can answer.
It does not establish that the property floods. Plenty of Auckland sections have a flow path along a boundary or across a corner of the lawn and no history of water anywhere near the house. The finding tells you a constraint exists on the land; it does not tell you what it has cost anyone.
How PropertyKete checks it, and where
PropertyKete is designed to help with early property research, particularly before you make an offer or decide what needs deeper investigation. The overland flow path check is a good example of what that means in practice: it tells you quickly whether this is a live question for the address, so you can put it to the right person rather than discovering it at consent stage.
The check tests whether a mapped flow path intersects the parcel. Where we have not resolved a parcel boundary for the address, it tests a ten-metre radius around the address point instead — a deliberate choice that catches paths running very close by, and one worth knowing about when you read the result. Either way the finding names its source and the date the dataset was current.
Three different results, and only one of them is a result
Not detected means the layer was searched and this parcel is not in it. That is a real finding, and the strongest of the three — though the mapping is built from a LiDAR survey, so very minor surface flow below that resolution can still exist.
No result here means the check ran against a city where PropertyKete holds no flow path layer. The report says so rather than showing a clean result. Nothing has been ruled out.
Detected means a mapped path intersects the parcel. That is a prompt to find out what it means for this site, not a conclusion about the property.
Coverage is currently deepest in Auckland, because PropertyKete holds more Auckland-specific hazard and planning datasets than it does for anywhere else. For overland flow paths specifically, the table below is generated from the same coverage registry the city pages use, so it describes what the product does today rather than what it was described as doing when this page was written.
What to do when a flow path is found
The finding is a starting point, and the useful next moves are cheap. In rough order:
- Look at Auckland Council’s own stormwater and hazard viewer for the address. The council publishes the authoritative version of this mapping, and it is free to view.
- Order or read the LIM. It will show flow paths recorded against the property and any associated setback or stormwater requirements, alongside the consents and notices that give them context.
- Ask the vendor, through the agent, about ponding or surface water in heavy rain. It is a factual question they are obliged to answer honestly, and the answer is often more informative than the map.
- Get the property file if the LIM raises questions about what was built across or near the path. It holds the plans and inspection records the LIM only summarises.
- Where the path crosses a building footprint, a driveway, or anything you plan to change, a stormwater or civil engineer can review the options and tell you what the constraint costs in practice.
- If you intend to build, extend or subdivide, a planner can tell you what the setback and stormwater rules mean for that specific proposal, and your solicitor can advise on what to make the offer conditional on.
The order matters more than it looks. The free steps often settle the question entirely, and where they do not, they let you brief a professional precisely instead of paying one to find out what a map already said.
| City | Status | What that means |
|---|---|---|
| Auckland | Returns a result | Modelled routes surface water takes in heavy rain. A flow path crossing a section constrains where you can build more often than it floods a house. |
| Wellington | No result produced | Auckland Council overland flow paths only. No result is produced here. |
| Christchurch | No result produced | Auckland Council overland flow paths only. No result is produced here. |
Source: Auckland Council (dataset updated January 2025). See the full Auckland matrix.
The same finding, read on three real reports
Material findings, screening indicators, and planning overlays
Not all evidence is the same weight
A mapped flow path treated as direct, parcel-level evidence, alongside a broad screening layer on the same report — a clear read of what the finding is and is not.
Material hazard findings, and how severity differs between them
Two water findings, and why they are not the same problem
A flow path and a flood plain on one property, which is the clearest way to see why the two findings carry different urgency and go to different people.
A clean result is evidence, not a guarantee
Every check came back clear. Here is what that is worth.
A report where the flow path check ran and found nothing. Reading that precisely — searched and not present, rather than not looked for — is the whole skill.
Who can answer the questions a flow path raises
Each entry says why a flow path in particular sends you to that person, and what to actually ask when it does. These are routes, not walls — on a stormwater question the council, an engineer and a planner routinely end up in the same conversation. For what each profession covers more generally, the full due-diligence guide sets them out side by side.
The council
Why them: The council both publishes the mapping and applies it. Its own viewer is the authoritative version of any flow path a third-party report shows you, ours included, and the LIM is where a path recorded against the property appears alongside the requirements that attach to it.
What to ask: Ask for the LIM, and read its stormwater and land-features sections for recorded flow paths, overland flow setbacks and any stormwater conditions. Where a structure already sits on or near the path, request the property file for the consent plans and inspection records behind it.
An engineer, including geotechnical
Why them: A mapped path is modelled from a survey of the ground surface. What it costs — whether a building platform, driveway or garage floor can sit where you want it, and what it would take to work around the path — is a site question that needs someone standing on the site.
What to ask: Ask a stormwater or civil engineer to assess the flow path against the specific footprint you care about: whether the route can be accommodated, diverted or piped, what levels the design would need, and what the works would realistically cost.
A planner or resource management specialist
Why them: Flow paths feed setback and stormwater rules, and those rules bite on a proposal rather than on the land in the abstract. Whether your extension, minor dwelling or subdivision is affected is a plan-rules question before it is an engineering one.
What to ask: Ask what the overland flow path setback and stormwater provisions mean for the exact thing you intend to build, whether it would be a permitted activity or need consent, and what the council would expect to see in an application.
A solicitor or conveyancer
Why them: A flow path can affect what you are able to do with the land after settlement, which makes it a matter for the agreement rather than only for the plans. It is also where the consent history of anything already built across the path gets tested.
What to ask: Tell them the flow path exists and what you intend to build, and ask what the offer should be conditional on — council confirmation of setbacks, an engineer’s report, or evidence that existing work across the path was consented and signed off.
The agent
Why them: The vendor has watched the property in heavy rain and you have not. On a surface-water question, lived observation is often more informative than the map, and it is a factual question they are obliged to answer honestly.
What to ask: Ask whether water ponds or runs across the section in heavy rain, where it goes, whether any drainage or regrading work has been done, and whether the vendor holds a LIM, engineer’s report or consent documents relating to it.
What a PropertyKete flow path finding is not
- A LIM
- The council’s formal record of what it holds about the property, including flow paths recorded against it and the requirements that attach. We hold no equivalent of it.
- A site stormwater assessment
- Our check tests whether a mapped path intersects the parcel. What that means for a specific building, driveway or earthworks proposal is a site question an engineer answers.
- A consenting opinion
- We do not assess what would be granted consent. Mapped flow paths inform setback and stormwater rules; only the council and a planner can tell you how those apply to a proposal.
Checklist
- Checked whether the overland flow path check actually ran for this address, or returned no result.
- Viewed Auckland Council’s own stormwater and hazard mapping for the address.
- Read the LIM for recorded flow paths, setbacks and stormwater requirements.
- Asked the vendor about ponding or surface water in heavy rain.
- Obtained the property file where a structure sits on or near the mapped path.
- Confirmed that any building across or near the path was consented and signed off.
- Engaged a stormwater or civil engineer where the path crosses a footprint, driveway or planned work.
- Confirmed setback requirements with the council before committing to any build or earthworks.
- Told the solicitor what the flow path affects, so the offer’s conditions reflect it.
A mapped flow path is one of the more useful things a screening report can tell you, precisely because it is so often actionable and so rarely dramatic. It rules nothing out and condemns nothing; it says there is a constraint on this land worth understanding before you plan around it.
And the reading that matters most is the quiet one: a check that did not run has told you nothing at all. Where the report says no result rather than not detected, the question is still open.
This guide is general information, not advice
It describes how overland flow paths are mapped and used in Auckland. It is not legal, engineering, insurance, valuation or financial advice, and it does not take account of your circumstances or of any particular property. Every decision in it should be made with the relevant professional named above.
The full due-diligence guide · Reading flood risk · What a LIM covers · Auckland coverage · Data sources