How to use Japanese hazard maps
Flood, inland flooding, tsunami, liquefaction, landslide, and their limitations.
Official hazard maps show modeled flood, inland-flood, landslide, tsunami, storm-surge, liquefaction, and active-fault exposure — use them, but they describe scenarios and do not prove an uncolored site is risk-free, so combine them with local maps and site observation.
Key points
- Check flood, inland-flood, landslide, tsunami, storm-surge, and liquefaction exposure.
- Hazard maps describe modeled scenarios, not guarantees.
- Being outside a colored zone does not prove the site is safe.
- Combine official maps with local maps and on-site observation.
What hazard maps show
Disaster screening should include official flood, inland-flood, landslide, tsunami, storm-surge, liquefaction, active-fault, and evacuation information. Japan’s hazard-map portals and MLIT’s Real Estate Information Library make this data accessible for a specific address, so you can see modeled exposure before you commit. Check every relevant hazard for the site, not just the most obvious one — a property away from a river can still face inland flooding, liquefaction, or landslide risk depending on the terrain.
Their limitations
Hazard maps describe modeled scenarios and do not prove that an uncolored site is risk-free — the models rest on assumptions, and real events can exceed them. Being outside a colored zone is reassuring but not a guarantee, so supplement the official maps with local maps and site observation: walk the site, note the slope and drainage, look at how water would flow in heavy rain, and ask neighbors about past flooding. Use the maps as one strong input into a broader judgment, not as the final word on safety.
Key points to carry away: Check flood, inland-flood, landslide, tsunami, storm-surge, and liquefaction exposure; Hazard maps describe modeled scenarios, not guarantees; Being outside a colored zone does not prove the site is safe; Combine official maps with local maps and on-site observation. Use the linked guides and calculators for the full decision, and confirm anything material with the lender, a licensed broker, a judicial scrivener, or a tax accountant before you act.
Who this is for
- Buyers screening disaster risk
- Investors assessing a site
What this is not
- A guarantee of safety
- Being outside a hazard zone does not mean safe; models can be exceeded, so combine maps with site observation.
Frequently asked questions
What is a hazard map?
An official modeled map of specified disaster exposure such as flood, tsunami, and liquefaction.
Does being outside a hazard zone mean safe?
No. Models can be exceeded, so combine maps with site observation.