Japan publishes some of the best natural-hazard mapping in the world, and it is free. The problem for a foreign buyer is that the main portal is in Japanese and assumes you know what the colours and terms mean. This guide does two jobs. It explains what the hazard results on an Engawa listing page mean, and it shows you how to read the government map yourself, so you can look at a plot before you fall for it.

One thing first. A hazard result on a listing is a first look from government maps. It is not a survey, it is not advice, and it does not tell you a house is safe. It tells you where to look harder.

What does the hazard section on a listing page show?

Almost every listing now has an "Area and hazard data" section. It shows flood, landslide and tsunami results for the point on the map, using national government data. It also shows the chance of a strong earthquake from the national J-SHIS model, plus ground, snow and farmland notes where they apply.

At the top of the section you will see a one-line count, for example:

6 checks clear, 1 to know about. Each check is against a government map for this exact point. Where a map is missing or we can't use it, we say so; that never means there's no risk.

Each row has a label, a short plain-English line, and a source. The label is always written out in words, never only a colour. These are the labels you will meet:

  • Checked, clear
  • Caution
  • Warning
  • Note
  • Not checked
  • Not applicable

What does "Checked, clear" mean?

It means we looked this plot up on the government map for that hazard, and the plot is not inside a mapped zone. For example:

Landslide risk. Checked, clear. Checked: no designated landslide zone at this location. Zone edges are approximate, and this is not a legal property disclosure document.

Flood risk. Checked, clear. Checked: outside a mapped flood area. The maps cover designated rivers only, so this is not a promise of no flooding.

Tsunami risk. Checked, clear. Checked: no designated tsunami inundation zone at this location

Read these narrowly. "Clear" means no flag on that one map for that one hazard. Zone edges are approximate. The flood maps cover designated rivers only, so a small stream, a drain or heavy rain on flat ground may not be on the map at all. Clear is not "no risk".

What does a result in a zone look like?

When the plot is inside a mapped zone, the row is marked Caution or Warning. Flood and tsunami rows give the depth of water the government model expects. Real examples from live listings:

Flood risk. Warning. Within a mapped flood area, water 3 to 5 m

Tsunami risk. Warning. In a tsunami inundation zone, expected depth at least 3.0 m

Flood risk. Caution. Within a mapped flood area, water under 0.5 m

Tsunami risk. Caution. In a tsunami inundation zone, expected depth up to 0.3 m

Flood depth bands on a listing run: water under 0.5 m, 0.5 to 3 m, 3 to 5 m, 5 to 10 m, 10 to 20 m, and over 20 m. Under 3 m is marked Caution. 3 m and over is marked Warning. Some listings near the coast also show a storm-surge row in the same style.

Landslide rows use the government's two categories. A yellow zone is marked Caution and reads:

Landslide risk. Caution. In a yellow (caution) landslide zone (2 zone(s)). Expect a surveyor to look at the slope behind the house. Zone edges are approximate, and this is not a legal property disclosure document.

A red zone is the highest category and is marked Warning. It is a formal, mapped designation, not a vague worry. Treat either colour as a reason to ask a local professional about that exact plot before you go further.

These are modelled scenarios from official maps. They show what the government model says could happen at that point. They do not predict a particular storm or wave.

What does "Not checked" mean, and why do some listings have it?

"Not checked" means we have no usable result for that hazard at that point. It is not a clear result. It does not mean low risk. Every "Not checked" row says so on the page. There are two reasons, and the row tells you which one applies:

  • No official map covers the area. Example, from a listing in Kagawa: "No official map covers this area, so we can't check tsunami risk, but that doesn't mean there's no risk."
  • We haven't been able to check yet. This covers a map we have not loaded yet, and a listing where the location is missing or too rough to place on a map. The row reads: "We haven't been able to check [hazard] here yet, but that doesn't mean there's no risk."

One label looks similar but is different. "Not applicable" is used for tsunami in a prefecture with no coast: "Inland, no tsunami map. This home is in a prefecture with no coast." There is nothing to check, so there is no gap.

If a listing says "Not checked" for something you care about, do not treat it as good news. Use the steps below, or email a founder and we will look at it with you.

How do I read the government hazard map myself?

The main national portal is the hazard map site run by Japan's Geospatial Information Authority (GSI), known as disaportal. It overlays official government hazard data (flood, landslide, tsunami, and more) on a map, so you can search an address or point and see which risks apply there. It is authoritative and free, though the interface is in Japanese.

You can reach it at the MLIT and GSI hazard map portal (disaportal). It offers a "layered" hazard map that stacks several risk types on one view, and links out to individual municipalities' own hazard maps. For a buyer, the layered map is the quickest way to see, for one plot, whether it sits in a flood, landslide, or tsunami zone at the same time.

How do I read the flood layer on the portal?

The flood layer shades areas by expected inundation depth under a design storm, using colour bands. Darker or more intense shading means deeper expected flooding. A house in a coloured band sits in a mapped flood-risk area; a house on unshaded ground does not show a mapped flood area on that layer.

To read it carefully, focus on two things: whether the plot is shaded at all, and, if so, which depth band it falls in. A plot at the edge of a shallow band is a very different proposition from one deep inside a deep zone. Remember that this is a modelled design-storm scenario, not a prediction of a specific flood.

On the portal, switch on the flood ("kouzui") layer for a specific address, using either the flood-only view or the combined layered view. Where the government has mapped a river's flood risk, the plot is shaded using an official depth-rank code: the two published rank systems run either in five steps (under 0.5 m, 0.5 to 1 m, 1 to 2 m, 2 to 5 m, and 5 m or more) or seven steps (under 0.5 m, 0.5 to 1 m, 1 to 2 m, 2 to 3 m, 3 to 4 m, 4 to 5 m, and 5 m or more), depending on which system the river's managing authority used. Shading gets progressively darker as the rank rises, matching the on-screen legend for the layer you have enabled. These are the same official rank codes published in MLIT's National Land Numerical Information flood-inundation dataset, so the band a plot sits in is a specific, checkable government figure.

An unshaded plot can mean two different things, and the map does not always make the difference obvious. It can mean the plot is in an area with flood data and sits outside every depth band. Or it can mean the layer has no data there at all: the underlying dataset leaves out any river whose managing authority has not supplied flood-modelling data, or whose original hazard map showed no inundation area to digitise, and disaportal's own documentation notes that some prefectures are still producing flood maps, so only partial data is published so far. Read the layer's own coverage notes before assuming a blank area means no risk. If a whole stretch of countryside looks blank rather than showing a shaded zone with a clear edge, that is more often a coverage gap than a finding of no risk.

How do I read the landslide layer on the portal?

The landslide layer marks sediment-disaster risk areas, typically on and below steep slopes. Japan designates warning areas and, for more severe risk, special-warning areas, and the map shades these. A house on or just below a shaded slope sits in a designated sediment-disaster zone, which is a formal, mapped designation.

The distinction between an ordinary warning area and a special-warning area matters, because the latter reflects a higher assessed risk to buildings and can carry stronger implications for what work is required or permitted. Many affordable rural akiya sit in valleys and on hillsides, so this layer comes up often. A designation is a reason to get specific local professional advice for that plot, not a detail to skim past.

How do I read the tsunami layer on the portal?

The tsunami layer shades coastal areas within the modelled tsunami inundation zone, again by expected depth. If a low-lying coastal plot is shaded, it is inside the zone the government models a tsunami could reach; if it is above and outside the shading, it is not. As with flooding, depth bands indicate how severe the modelled inundation is.

The mental model for tsunami risk is "rare but severe." Unlike flooding, which recurs, a tsunami is a low-frequency, high-consequence event, so a coastal house can be lovely and still sit inside the modelled reach. The map's job is simply to tell you whether the specific plot is in that reach, which is the fact you want before, not after, you commit to a coastal house. For the wider safety picture, see is it safe to buy an akiya.

What if the map is confusing or the plot sits on a boundary?

Zoom to the exact plot rather than the neighbourhood, check each hazard layer separately, and when a plot sits on the edge of a zone, treat it as inside for planning purposes and get local advice. If you cannot read the Japanese labels, use the colour bands and the layer you have enabled to orient yourself, and confirm anything material with a professional.

Boundary cases are common and genuinely ambiguous, so the honest approach is caution. A plot on the edge of a flood or landslide zone deserves the same attention as one clearly inside it. Do not talk yourself into the reassuring reading.

Remember too that many listings only name a neighbourhood, so the point on our map can be approximate. Zone edges are approximate as well. Always check the exact plot yourself once you know the address.

What should I do after reading a hazard result?

A hazard result is where your own checking starts. Whatever the listing says (clear, in a zone or not checked), do these things before you commit:

  1. Ask the municipality. Contact the town office, or the akiya bank named on the original listing, and ask what hazard information it holds for the exact address. Many towns publish their own hazard map, often more detailed than the national layers, and they can tell you about local conditions the national maps do not cover.
  2. Open the local hazard map and the portal and look at the exact plot yourself, layer by layer, as described above.
  3. Ask a local professional. A qualified local agent, building surveyor or architect can look at the ground, the slope, the drainage and the building itself. Do this for any plot in or near a zone, and for any "Not checked" result you care about.
  4. Ask about insurance and about what building work is allowed on the plot. Both can change if a plot is in a designated zone.
  5. Visit if you can, or have someone you trust visit for you. A map cannot tell you the roof is sound or that a stream runs behind the house.

We are not a surveyor and we do not give legal advice. We map what the government maps show, in plain English, and we link the source so you can check it.

How we know this

Engawa reads these same government hazard layers programmatically and attaches them to each listing, so you get the flood, landslide, and tsunami findings for a specific plot in plain English, with a link back to the source, rather than having to navigate a Japanese portal yourself. We pair these with seismic-hazard data from J-SHIS, the national seismic hazard station. Where a plot falls outside every mapped zone, or where a layer's data is thin, we show an honest null with its source, never an all-clear we cannot support. We map risk; we do not visit sites, so a survey still matters.

Frequently asked questions

Is the hazard portal available in English?

The main national portal is primarily in Japanese, which is a real barrier for foreign buyers. Some municipalities publish English hazard information, and the colour bands are readable without language, but full interpretation often needs translation or help. This is exactly why we show the findings in plain English on each listing.

Does "Checked, clear" mean zero risk?

No. It means no flag on that map for that hazard at that point. Hazard maps model design scenarios, and reality can exceed them. The flood maps cover designated rivers only. Zone edges are approximate. Treat clear as "no flag raised on this layer", not "no risk", and still get local advice.

Does "Not checked" mean the house is fine?

No. It means we have no usable result for that hazard there. The row says why: no official map covers the area, or we haven't been able to check yet. It is a gap in what we know, not a good sign.

What is the difference between a warning area and a special-warning area?

Both are designated sediment-disaster (landslide) zones, but a special-warning area reflects a higher assessed risk to buildings and can carry stronger regulatory implications. On a listing, a yellow zone is marked Caution and a red zone is marked Warning. A plot in either deserves specific local professional advice before you buy.

Can I rely on the hazard result alone?

No. It is a first look that tells you which risks a plot faces on paper. The actual condition of the ground and the building needs a site visit and a qualified local professional. Use the result to decide where to look harder, then get expert eyes on the specific property.

What if I think a result on a listing is wrong?

Tell us. A founder will check it against the source.

The honest bottom line

Japan's hazard maps are excellent and free, and nearly every Engawa listing now shows the flood, landslide and tsunami result for its point, in plain English, in the Area and hazard data section, with the source on the page. Use that as a first look. Then ask the town, read the local hazard map, check the exact plot yourself, and get a local professional to look at the ground and the building. Where a listing says "Not checked", read it as "we don't know yet".

Start with Kagoshima or Oita and open any listing to see it, or email a founder to talk through a specific plot. Flat fee, no commission.