Direct answer: Before you make an offer on any Japanese property, look it up on two free government tools: the Hazard Map Portal Site (ハザードマップポータルサイト) run by the Geospatial Information Authority of Japan, and the Real Estate Information Library run by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT). Together they show expected flood depth, landslide warning zones, and tsunami inundation for the exact address — information that is legally required to be shown to you for flood risk only, and often left out of the listing for everything else.
The primary tool is disaportal.gsi.go.jp, which hosts the "重ねるハザードマップ" (overlay hazard map). It lets you stack flood/inundation (洪水・内水), landslide/sediment disaster (土砂災害), storm surge (高潮), and tsunami (津波) layers on one map, plus municipal-level "わがまちハザードマップ" links. The interface is Japanese-only, but you do not need to read Japanese to use it:
The second tool, reinfolib.mlit.go.jp (不動産情報ライブラリ), is MLIT's property-data platform. It has an English-language option and covers transaction price history, urban planning designation, and other disaster-prevention reference data by address, which is useful for cross-checking zoning alongside the hazard layers above. It complements, but does not replace, the hazard map portal's flood, landslide, and tsunami overlays.
The flood layer on disaportal.gsi.go.jp is based on the "assumed maximum scale" (想定最大規模) rainfall scenario — the largest flood a river is modeled to produce, not an average-year event. Depths are shown in four color bands, and what each one means for daily life is roughly:
These bands describe an assumed worst-case event over the river's watershed, not a certainty for any given year — but they are the same data set that a licensed agent is required to show you (see below), so it is worth reading it yourself before that meeting rather than relying on a verbal summary.
Under Japan's Act on Sediment-Related Disaster Countermeasures (土砂災害防止法), municipalities designate two tiers of landslide-prone land, both visible on the same hazard map portal's 土砂災害 layer:
Many akiya sit on hillside or valley-edge lots precisely because that land was cheap to build on decades ago — which is also why it is disproportionately likely to fall inside one of these zones today. The zone status is not always visible from the road, and older listings rarely mention it, so this is a layer worth checking even when a property looks flat and unremarkable in photos.
For any property near a coastline, the same hazard map portal has a separate 津波 (tsunami) layer, also based on an assumed maximum-scale scenario set by each prefecture. Like the flood layer, it is shown as color-coded depth bands over the modeled inundation area. Coastal akiya — including many in scenic fishing-village locations popular with overseas buyers — can carry meaningful tsunami exposure even where flood-river risk is low, so check this layer independently rather than assuming "not on a river" means "no water risk."
Since August 28, 2020, Japan's Building Lots and Buildings Transaction Business Act enforcement regulations (宅地建物取引業法施行規則) have required a licensed agent to show the buyer or tenant the property's approximate location on the local flood hazard map as part of the mandatory Important Matters Explanation (重要事項説明) — announced by MLIT on July 17, 2020. In practice, this means the agent should point out the property's position on the flood/inundation map and, ideally, nearby evacuation shelters, before you sign a contract.
The catch: this legal disclosure duty covers flood hazard maps specifically. It does not extend to landslide (土砂災害) zones or tsunami (津波) inundation maps, and it says nothing about foundation-level flood-proofing, drainage history, or how the map has changed since the last update. Checking those layers yourself on disaportal.gsi.go.jp — before the explanation meeting, not during it — is the only way to catch what falls outside the mandatory disclosure.
Japanese property listings (物件概要) are built around structural facts — floor area, land category, road frontage, build year — because that is what the listing template and portal fields ask for. Hazard-map status is a separate lookup an agent performs manually at the Important Matters Explanation stage, generally only for flood risk, and generally only once you are already far enough into the process to be sitting across from them. If you are still comparing several akiya candidates by URL, that conversation may be weeks away — which is exactly when it is most useful to already know the answer. The same is true for other risks that don't appear in a standard listing, such as rebuild-prohibited (再建築不可) status, which has nothing to do with hazard maps but is just as absent from the listing headline, or basic questions of whether foreign nationality affects the purchase at all, which it generally does not.
Want a second data point before you check the map yourself? Start with the free 12-point akiya risk checklist — it covers hazard exposure alongside the other things a listing tends to leave out. If you already have a specific property in mind, a $49 risk report pulls the flood, landslide, tsunami, zoning, and transaction data for that exact address into one PDF, with the questions to send the agent.
The main hazard map portal (disaportal.gsi.go.jp) and its overlay tool are Japanese-only. You can still use them without reading Japanese by searching the address in Latin letters or pasting coordinates, then reading the color-coded legend, which follows a consistent national color scale for flood depth, landslide zones, and tsunami inundation. A browser translator extension can translate menu labels, but always verify colors and legend values against the original Japanese key.
No. Hazard maps model expected scenarios based on historical rainfall, river capacity, and topography, but they do not cover every possible event, and some municipalities have not mapped every hazard type. A blank area can mean low modeled risk, or it can mean the map has not been updated with the latest data. Always cross-check the flood, landslide, and tsunami layers separately and confirm directly with the municipality's disaster-prevention section.
Since a rule change to the Building Lots and Buildings Transaction Business Act enforcement regulations took effect on August 28, 2020, licensed agents in Japan must show the property's approximate location on the local flood hazard map during the Important Matters Explanation (重要事項説明) before a purchase or lease contract is signed. This covers flood hazard maps only; it does not require disclosure of landslide or tsunami zone status, so buyers should check those layers themselves.
Have a specific listing in mind? Get the official zoning, hazard and transaction data for that exact lot — plus the questions to send the agent — in one PDF.
Get a $49 risk report Free 12-point checklistThis guide is general information based on public sources cited above. It is not legal, tax, or real-estate brokerage advice. Confirm every item for a specific property with the agent, the municipality, and licensed professionals.