As flood risks increase in recent years, this guide explains how to check inundation risk using hazard maps before selecting a rental property. Learn how to use the Ministry of Land, Infrastructure, Transport and Tourism's Hazard Map Portal, how to read flood inundation zones, and key points for choosing properties with lower risks.
Reviewed by: Nobuyuki MoriPresident, M-Assets Co., Ltd. / Licensed Real Estate Transaction Specialist (Miyagi #018212)
This guide explains flood and inundation risks to verify when selecting rental properties and how to read hazard maps. We cover everything from accessing the Ministry of Land, Infrastructure, Transport and Tourism's Hazard Map Portal and understanding flood risk disclosures in property transaction documents, to decision-making criteria for 1st and 2nd floor units and flood insurance considerations—a complete roadmap to safe rental selection.
With recent increases in heavy rainfall and typhoon damage, assessing flood risk has become essential when choosing a rental property. This guide explains practical methods used by real estate professionals—from reading hazard maps to on-site verification tips and what to do in the event of damage.
A practical guide to protecting your rental home from flooding caused by typhoons and heavy rain. We cover advance preparation, evacuation decision-making, what to do when damage occurs, and insurance claims—all essential knowledge for residents of lower floors and flood-risk areas.
In recent years, flood damage from typhoons, sudden downpours, and river flooding has increased. When selecting a rental property, it's becoming increasingly important to check not only location and rent, but also "flood risk." If you experience flooding after moving in, the damage to your possessions, temporary relocation costs, and emotional stress are immeasurable.
A hazard map is a map that indicates areas expected to be affected by natural disasters (floods, landslides, tsunamis, earthquakes, etc.), the degree of potential damage, evacuation routes, and similar information.
URL: https://disaportal.gsi.go.jp/
On this portal site, you can check various hazard maps for floods, internal flooding, landslides, tsunamis, and storm surge nationwide in one place. You can search by address or location on the map, and it's free for anyone to use.
It shows the expected flood inundation zones and flood depths in case of river flooding. Color coding is typically as follows:
| Color | Flood Depth | Risk Level |
|---|---|---|
| White/Light Yellow | Less than 0.5m | Low (below-floor-level flooding) |
| Yellow to Orange | 0.5–3.0m | Moderate (1st–2nd floors may flood) |
| Red to Purple | 3.0–5.0m or more | High (2nd floor and above may be submerged) |
A flood depth of 3m or more is deep enough to completely submerge the 1st floor of a wooden 2-story building. Special caution is needed when living on the 1st floor in these areas.
It shows the risk of "internal flooding," which occurs when rainwater drainage systems cannot keep up, rather than overflow from rivers. Internal flooding can occur even in major metropolitan areas during sudden heavy downpours, and low-lying areas and underground spaces are particularly at risk.
It indicates the risk for properties located on steep slopes or near mountain streams.
We strongly recommend avoiding moving into properties within Red Zones.
Search the property address on the portal site and overlay the flood, internal flooding, and landslide layers to verify.
Hazard maps created and distributed by local municipalities may contain more detailed information (evacuation centers, evacuation routes, etc.). They are often available for download from the municipality's official website.
Even within the same flood inundation zone, risk varies greatly depending on the floor level.
| Floor | Flood Depth 1m or Less | Flood Depth 1–3m | Flood Depth 3m or More |
|---|---|---|---|
| 1st Floor | Risk of floor-level flooding | Complete inundation | Submersion |
| 2nd Floor | Relatively safe | Risk of floor-level flooding | Risk of complete inundation |
| 3rd Floor and Above | Safe | Safe | Relatively safe |
If choosing a rental within a flood inundation zone, selecting a property on the 2nd floor or higher significantly reduces risk.
Since August 2020, it has been mandatory to explain "the location of the target property on the flood hazard map" in the Important Matters Disclosure for real estate transactions. You can receive an explanation from the real estate company during the Important Matters Disclosure before signing the contract.
Flood Barriers and Water Sandbags
Check Drainage Outlets
Protect Your Belongings
Check whether your fire insurance policy includes "water damage coverage" when you move into a rental. Many plans do not include water damage coverage, so if you live in an area with flood risk, we strongly recommend choosing a plan with water damage coverage.
Sample coverage includes:
Areas matching the following tend to have high flood risk:
We recommend also checking topographic maps and elevation maps (GSI Maps).
Verifying flood risk is one of the important criteria when selecting a rental property. Using the Ministry of Land, Infrastructure, Transport and Tourism's Hazard Map Portal allows you to check for free and easily, and you can understand flood inundation zones, flood depths, and landslide risk at a glance. When choosing a property in a risky area, prioritize 2nd-floor-and-above units, and don't forget to ensure your fire insurance includes water damage coverage.
不動産ネットワーク
投資物件・賃貸住宅・テナント・運営会社をつなぐ不動産4サイト連携。
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