Guide
Reading flood risk on a New Zealand property report
Flood findings are the ones buyers most often read as a verdict — in or out, settled either way. They are neither. Each one is a model of a particular kind of water behaving in a particular way, and knowing which model you are looking at is most of the skill.
Part of How to research a property before buying in New Zealand.
Three different things, all called flood risk
Water reaches a property in more than one way, and the maps describing those ways are made separately, mean different things, and arrive as separate findings. Reading a report well starts with knowing which of them you are looking at, because the answer changes who you ring and what you ask them.
The three you will meet
- Flood plain — a modelled extent of standing water from rainfall and rivers. This is the one people mean by “the flood zone”, and the one insurers and lenders react to most directly.
- Overland flow path — a modelled route surface water takes across the ground on its way downhill. It usually shapes what you can build, and where, rather than whether the house takes water.
- Coastal inundation — modelled flooding from the sea, which behaves differently again and is often modelled twice: once at today’s sea level and once under a sea-level-rise scenario.
A property can carry one of these and none of the others. It is entirely ordinary for a section to have a flow path along one boundary, sit well outside any flood plain, and be nowhere near the coast — and equally ordinary for a coastal property to have no flow path at all. Treating the three as one number is how a modest constraint gets read as a catastrophe, and how a real one gets missed.
Flow paths are the least well understood of the three. Overland flow paths: what a mapped path constrains covers them on their own.
What the numbers on a flood map actually mean
Flood extents are usually published for a storm of a stated rarity. A 1% annual exceedance probability event — 1% AEP — is one with a one-in-a-hundred chance of being equalled or exceeded in any given year. It is a statistical description of a storm, not a schedule.
The “once in a hundred years” misreading
A 1% AEP flood is not one that happens once a century, and having had one does not use up the next hundred years. Two can occur in consecutive years, or in the same year, without anything about the statistics being wrong.
The probability also describes the storm, not your house. Whether that storm puts water through a particular building depends on ground levels, floor heights, drainage and what has been built nearby — none of which a regional extent map knows.
Two further properties of these maps matter more than the percentage. They are modelled rather than observed: they describe where water would go given the terrain and the assumptions in the model, not where it has been. And they are drawn at a scale that suits a region, so a boundary line on the map is a modelled edge rather than a surveyed one — a property just outside it is not meaningfully different from one just inside.
Models are also revised. Councils update flood modelling as survey data, rainfall assumptions and stormwater networks change, and a property’s mapped status can move without anything physical happening to the land. That is a reason to look at the council’s current published version rather than a copy of it, ours included.
What a flood finding does and does not establish
A finding that a parcel intersects a mapped extent establishes exactly that: this land and this modelled layer overlap. It is real information and worth acting on. It is not a statement that the house has taken water, that it will, or that it cannot be insured.
What it is genuinely useful for
- Deciding that insurance is a question to settle early, in writing, for this specific address rather than in principle.
- Deciding that the council’s own record deserves a careful read, because a LIM shows what the council formally holds about flooding at the property.
- Deciding to ask the vendor a direct, factual question about water, which they are obliged to answer honestly.
- Deciding whether a build, extension or earthworks plan needs professional input before you commit to it.
- Deciding how hard to look at floor levels, drainage and any past remedial work during an inspection.
The reverse reading is the one that costs people money. A property outside every mapped extent has not been shown to be dry. Modelling covers the scenarios it was built for; it does not cover a blocked culvert, a neighbour’s regrading, a failed private drain, or a storm larger than the one modelled. Absence of a mapped extent is absence of a modelled extent, and nothing more.
Three 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 — within the limits of the model that produced the layer.
No result here means the check ran against a city where PropertyKete holds no layer at all. The report says so rather than showing a clean result. Nothing has been ruled out.
Detected means a mapped extent covers the parcel. That is a prompt to find out what it means for this site, not a conclusion about the property.
What PropertyKete checks, and where
PropertyKete is designed to help with early property research, particularly before you make an offer or decide what needs deeper investigation. On water questions that means telling you quickly which of the three layers is live for an address, so you can put the right question to the right person instead of arriving at it late.
Each check tests whether a mapped extent intersects the parcel. Where a parcel boundary has not been resolved for the address, it tests a small radius around the address point instead — a deliberate choice that catches extents 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.
Coverage is currently deepest in Auckland, because PropertyKete holds more Auckland-specific hazard and planning datasets than it does for anywhere else. 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 we never check anywhere
Tsunami evacuation and exposure zones are not part of a PropertyKete report for any address, in any city. No finding will ever appear, however the ground lies — so a report that says nothing about tsunami has said nothing about tsunami.
For a coastal property that is a real gap. Councils and regional civil defence groups publish evacuation zone mapping you can read directly, and it is worth doing.
| Check | Auckland | Wellington | Christchurch |
|---|---|---|---|
| Flood plainA modelled extent of standing water in a storm of a stated rarity. This is the layer people mean when they say a property is “in the flood zone”. | Returns a result | No result produced | No result produced |
| Overland flow pathA modelled route that surface water takes across the ground on its way somewhere else. It constrains what can be built more often than it puts water through a house. | Returns a result | No result produced | No result produced |
| Coastal inundationModelled flooding from the sea, run twice where the data allows: at today’s sea level, and again under a one-metre rise. The second is a scenario rather than a forecast, and carries no date by which that rise occurs. | Returns a result | No result produced | No result produced |
- Flood plain source: Auckland Council (dataset updated January 2025).
- Overland flow path source: Auckland Council (dataset updated January 2025).
- Coastal inundation source: Auckland Council (January 2025).
See the full Auckland matrix, or the city pages for what a Wellington or Christchurch report does and does not return.
What to do when a flood finding appears
The finding is a starting point, and the first moves are cheap. In rough order:
- Look at the council’s own flood and hazard viewer for the address. The council publishes the authoritative version of this mapping, it is free to view, and it will be more current than any copy of it.
- Order or read the LIM. It is where flooding recorded against the property appears, alongside the consents, notices and drainage information that give it context.
- Ask your insurer or broker about this specific address, in writing, before you commit to anything. Availability, excess and premium can all differ from what you assumed, and lenders generally require cover to be in place.
- Ask the vendor, through the agent, whether water has entered the building or ponded on the section, when, and what was done about it. The answer is often more informative than the map.
- Look at floor levels and site drainage during the building inspection, and ask the inspector directly what they saw that relates to water.
- Where you intend to build, extend or regrade, a stormwater or civil engineer can assess what the mapped extent means for that plan, and a planner can tell you what the rules require of it.
The order matters more than it looks. The free steps often settle the question, and where they do not, they let you brief a professional precisely instead of paying one to find out what a public map already said.
Water-related checks we never run, anywhere
- Tsunami evacuation and exposure zones
- No tsunami dataset is held and no tsunami check runs, including for coastal addresses.
Water findings read on three real reports
Material hazard findings, and how severity differs between them
Two water findings, and why they are not the same problem
A flood plain and a flow path on the same property, which is the clearest way to see why two water 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.
Every water check ran and found nothing. Reading that precisely — searched and not present, within the limits of the model — is the hardest reading on this page.
Material findings, screening indicators, and planning overlays
Not all evidence is the same weight
Direct parcel-level water evidence sitting alongside a broad screening layer, and a useful illustration of how differently the two deserve to be weighted.
Who can answer the questions a flood finding raises
Each entry says why a flood finding in particular sends you to that person, and what to actually ask when it does. These are routes, not walls — on a water question the council, an insurer and an engineer 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 holds both the mapping and the record. Its viewer carries the current, authoritative version of any flood extent a third-party report shows you, ours included, and its files record what has actually been reported at the property rather than only what a model predicts.
What to ask: Order the LIM and read its flooding, drainage and land-features sections. Ask whether the property is subject to a recorded flood hazard, what minimum floor level or stormwater requirements apply, and whether the flood modelling for the area has been revised recently.
An insurer or broker
Why them: A mapped extent changes an insurance conversation more directly than almost any other finding, and insurance is generally a condition of lending. This is the question most worth settling before you are committed rather than afterwards.
What to ask: Ask for confirmation in writing for this exact address rather than an indicative quote: whether cover is available, at what premium, with what excess for water damage specifically, and whether any exclusion or condition applies.
A building inspector
Why them: Whether water has reached a building, and what it left behind, is a question about the building — floor levels relative to the ground, site drainage, subfloor condition, and the marks past water leaves in places a map cannot see.
What to ask: Tell the inspector about the flood finding before the inspection so they look for it, and ask what they observed about floor levels, drainage, subfloor moisture and any evidence of past water entry or remedial work.
An engineer, including geotechnical
Why them: A regional flood model describes an area. What it means for a specific building platform, floor level or earthworks proposal is a site question, and one that needs someone standing on the site with the levels in front of them.
What to ask: Ask a stormwater or civil engineer to assess the site against the mapped extent: actual ground and floor levels relative to the modelled water level, what mitigation is feasible, and what it would realistically cost.
The agent
Why them: The vendor has watched the property through storms and you have not. On flooding, lived observation fills exactly the gap a model leaves, and it is a factual question the agent is obliged to answer honestly.
What to ask: Ask whether water has ever entered the building or ponded on the section, when it last happened, what was done about it, and whether the vendor holds a LIM, insurance history, engineer’s report or drainage records relating to it.
A solicitor or conveyancer
Why them: Flooding reaches the agreement through the conditions written into it — insurance, the LIM, and anything the council has formally recorded against the property that will bind you as the new owner.
What to ask: Tell them what the report found and ask what the offer should be conditional on: written insurance confirmation for the address, a satisfactory LIM, or a professional assessment where one is warranted.
What a PropertyKete flood finding is not
- A LIM
- The council’s formal record of what it holds about the property, including flooding recorded against it and any floor-level or stormwater requirements that attach. We hold no equivalent of it.
- An insurance decision
- We have no visibility of any insurer’s appetite, terms or pricing for an address. Whether this property can be covered, and on what terms, is something only an insurer can tell you.
- A site flood assessment
- Our checks test whether a modelled extent covers the parcel. Actual ground and floor levels, and what a modelled water level means for a specific building, are site measurements an engineer takes.
- A record of what has happened
- We hold no history of water at a property. Mapped extents are modelled from terrain and rainfall assumptions rather than compiled from events, so nothing here tells you whether water has ever reached the house.
Checklist
- Identified which of the three water findings the report is actually showing — flood plain, overland flow path, or coastal inundation.
- Checked whether each water check ran for this address, or returned no result because no layer is held.
- Viewed the council’s own current flood and hazard mapping for the address.
- Read the LIM for recorded flooding, minimum floor levels and stormwater requirements.
- Obtained written confirmation from an insurer for this address, including the water-damage excess.
- Asked the vendor whether water has entered the building or ponded on the section, and what was done about it.
- Asked the building inspector specifically about floor levels, drainage and any evidence of past water entry.
- Engaged a stormwater or civil engineer where a mapped extent affects a building platform or planned work.
- Confirmed any minimum floor level or stormwater requirement with the council before committing to a build.
- Checked the council’s tsunami evacuation mapping directly for a coastal property, since no report here covers it.
- Told the solicitor what the water findings were, so the offer’s conditions reflect them.
Flood mapping is one of the more useful things a screening report can surface, and one of the easiest to over-read. A mapped extent is a model of a storm meeting a landscape — good enough to tell you the question is live, never precise enough to answer it for a particular house.
And the quiet reading matters most here too: a check that did not run has told you nothing at all. Where a report says no result rather than not detected, the question is still entirely open.
This guide is general information, not advice
It describes how flood, flow path and coastal inundation mapping is produced and read. 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 · Overland flow paths in detail · What a LIM covers · Auckland coverage · Data sources