1. What Is a Hazard Map?
A hazard map (hazaado mappu / ハザードマップ) is a map that shows areas where natural disaster damage is predicted to occur. It allows you to visually confirm various disaster risks, including flooding, inland water flooding, landslides, tsunami, and storm surges.
Hazard maps are created and published by municipal governments. In real estate transactions, a 2020 amendment to Japan's Real Estate Brokerage Act enforcement regulations made it mandatory for agents to explain the property's location on flood hazard maps during the important matters explanation (juyo jiko setsumei).
Important Regulatory Change
Since August 2020, real estate agents in Japan are required to explain the property's position on flood hazard maps during the important matters explanation. If this explanation is not provided, be sure to ask for it.
2. How to Use the MLIT Hazard Map Portal Site
The "Hazard Map Portal Site" operated by Japan's Ministry of Land, Infrastructure, Transport and Tourism (MLIT) provides centralized access to hazard map information for the entire country. Two main services are available:
Overlapping Hazard Map (Kasaneru Hazard Map)
This tool lets you overlay multiple disaster risk layers -- flood, landslide, tsunami, road disaster information, and more -- on a single map. Simply enter an address to see all disaster risks for that location at a glance.
My Town Hazard Map (Wagamachi Hazard Map)
A directory of links to hazard maps created by each municipality. Use this when you need more detailed, area-specific information.
Basic Steps
- 1Visit the Hazard Map Portal Site and select "Overlapping Hazard Map" (Kasaneru Hazard Map)
- 2Enter the address you want to investigate in the search bar
- 3Select the disaster type (flood, landslide, etc.) from the left-side menu
- 4Review the color-coded risk zones displayed on the map
3. Understanding Flood Inundation Zones
Flood inundation zones indicate the areas predicted to be flooded and the expected depth of inundation if a river overflows. They are color-coded by estimated inundation depth.
| Inundation Depth | Risk Level | Expected Damage |
|---|---|---|
| Less than 0.5m | Low | Possible below-floor flooding |
| 0.5m to 3.0m | Moderate | First floor above-floor flooding; evacuation needed |
| 3.0m to 5.0m | High | Possible flooding up to second floor; early evacuation essential |
| 5.0m or more | Very High | Flooding above second floor; life-threatening danger |
Watch Out for Inland Water Flooding
In addition to river flooding, "inland water flooding" (naisui hanran) -- caused by torrential rain exceeding the capacity of the sewage system -- is another flood risk. This is particularly important in urban areas. Some municipalities publish separate inland water flooding hazard maps.
4. Understanding Landslide Warning Areas
Landslide warning areas are designated by prefectural governors under the Sediment Disaster Prevention Act (Doshasaigai Boshiho). Two levels of designation exist:
Landslide Warning Area (Yellow Zone)
An area where residents' lives or safety may be endangered if a landslide occurs. Warning and evacuation systems must be established. Disclosure is required during the important matters explanation in real estate transactions.
Landslide Special Warning Area (Red Zone)
An area where buildings may be destroyed and residents' lives may be at serious risk if a landslide occurs. Subject to restrictions on certain development activities, structural regulations for buildings, and potential relocation advisories.
5. Tsunami and Storm Surge Hazard Maps
If you are considering properties in coastal areas, it is important to also check tsunami hazard maps and storm surge hazard maps.
- ●Tsunami hazard maps: Show the expected inundation zones in the event of a maximum-class tsunami. You can also check the locations of tsunami evacuation buildings and evacuation routes.
- ●Storm surge hazard maps: Show areas predicted to be flooded by storm surges caused by typhoons. Particular caution is needed along the coasts of Tokyo Bay and Osaka Bay.
6. Checking Disaster Risk on JikoDB
JikoDB automatically assesses and displays disaster risk for each property based on MLIT hazard map data. You can check the following information in the "Disaster Risk" section of each property's detail page:
Flood Inundation Estimate
The estimated inundation depth at the property's location is automatically retrieved and displayed with a risk level. Based on flood inundation zone data published by MLIT.
Landslide Risk
Displays whether the property falls within a landslide warning area (Yellow Zone) or special warning area (Red Zone).
Tsunami Inundation Estimate
For properties in coastal areas, displays whether the property falls within a tsunami inundation zone.
About JikoDB's Automatic Disaster Risk Assessment
JikoDB periodically retrieves hazard map data published by MLIT and automatically assesses disaster risk based on each property's location. This information is available on property detail pages and through the area risk check feature, providing useful reference information for property selection.
7. Tips for Property Selection
Here are key points for using hazard maps when selecting a property.
- ●Check risk not only at the property location, but also along your commute route and around the nearest station
- ●For properties in flood inundation zones, consider the first-floor layout and whether to get flood insurance
- ●For properties in landslide warning areas, confirm evacuation routes in advance for heavy rain events
- ●Exercise extra caution with areas where multiple disaster risks overlap
- ●Hazard maps are updated periodically, so always check for the latest version
Related Pages
* The content on this page is for general informational purposes only and does not constitute legal advice. Hazard map information is based on projections, and actual disaster damage may exceed these estimates. For the latest information, please refer to your local government and the MLIT Hazard Map Portal Site.