Check Water Hazard Risks with Hazard Maps—Essential Disaster Prevention Check for Choosing Rental Properties
Water disaster risks are increasing in recent years. Be sure to check hazard maps before selecting a rental property. We'll explain how to read them, which areas to watch out for, and practical tips for choosing the right property.
In recent years, water-related disasters—including flooding, landslides, and inland flooding caused by heavy rains—have been increasing across Japan. When selecting a rental property, while many people check rent, floor plan, and amenities, surprisingly few confirm water disaster risks. Living in a flooded rental property can result not only in damage to furnishings but also in difficulty maintaining everyday life. In this article, as a real estate rental professional, I'll explain in detail how to use hazard maps, characteristics of high-risk areas, and key points to watch out for when choosing a property.
A hazard map is a map that shows the areas where damage is expected to occur in the event of a natural disaster (flooding, landslides, tsunamis, storm surge, etc.) and the extent of that damage. Created and published by municipalities, hazard maps can be checked online anywhere in the country through the Ministry of Land, Infrastructure, Transport and Tourism's "Hazard Map Portal Site (Overlay Hazard Maps)."
Main Types of Hazard Maps
・Flood Hazard Map: Shows the flooded area and depth in case of river overflow
・Inland Flooding Hazard Map: Shows projected flooding caused by rainwater exceeding the drainage capacity of sewers and similar systems
・Landslide Hazard Map: Shows areas at risk of landslides, debris flows, and ground collapse
・Tsunami Hazard Map: Shows projected tsunami inundation areas near coasts
・Storm Surge Hazard Map: Shows projected flooding from storm surge damage caused by typhoons and similar events
It is important to check multiple maps to understand what risks exist in the area you plan to live in.
How to Read a Hazard Map—Understanding Flood Depth Standards
On flood hazard maps, flood depth is indicated by color coding. General color coding standards are as follows:
・Less than 0.5 m (light yellow): Risk of flooding below floor level. The first-floor living space is less likely to be affected, but roads may be flooded
・0.5–1.0 m (yellow): Risk of floor-level flooding. Damage to first-floor living spaces
・1.0–2.0 m (orange): Risk of complete first-floor flooding. Evacuation may be necessary
・2.0–3.0 m (red): Risk of flooding up to the second-floor level. Life-threatening danger
・3.0 m or more (dark red/purple): Risk of flooding above the second floor. Extremely dangerous
For rental residents living on the first or second floors, areas with flood depths exceeding 0.5 m require particular attention.
Characteristics of Locations with High Water Disaster Risk
Before checking a hazard map, locations with the following geographical characteristics tend to have high water disaster risks:
Near Rivers, Low-Lying Areas, and the Lower Ends of Alluvial Fans
Land near rivers or land lower than surrounding areas (low-lying areas, valleys, depressions) are high-risk areas for flooding and inland flooding. Regions with place names containing characters such as "swamp," "pond," "valley," "river," "beach," "sandbank," "moat," or "field" may have historically been wetlands or marshy areas.
Hilly Terrain and Land Near Mountains
Land near slopes and mountain areas carries the risk of landslides. Areas designated as Landslide Warning Areas (yellow zones) or Special Landslide Warning Areas (red zones) require particular attention.
Areas with Low Elevation Above Sea Level
The Geospatial Information Authority of Japan maps show elevation. Zero-meter zones (areas at sea level or below) have particularly high water disaster risks and are widespread in major metropolitan areas such as Tokyo, Osaka, and Nagoya.
Practical Water Disaster Risk Checks When Choosing a Rental Property
① Check the hazard map before viewing the property
Once you have the property's address, first check it on the Ministry of Land, Infrastructure, Transport and Tourism's Hazard Map Portal Site or the municipal hazard map. By checking before viewing, you can avoid wasting time viewing properties in high-risk areas.
② Check the building structure and age
Check not only whether the building meets the New Seismic Standard (post-1981) but also the foundation height (the height of the floor from ground level). Buildings with higher foundations may avoid floor-level flooding in cases of minor water seepage.
③ Check the property's flooding history
Ask your real estate agent whether this property or the surrounding area has experienced flooding in the past. As of the August 2020 amendment to the Real Estate Brokerage Act Ordinance, real estate agents are required to explain the location's hazard map designation in the statement of important matters.
④ Consider purchasing water disaster insurance (property insurance)
Fire insurance, which is mandatory for rental properties, primarily covers fire damage, but you can add water disaster (flood, landslide, etc.) coverage as an option. If you live in an area with high water disaster risk, we strongly recommend purchasing property insurance with water disaster coverage included.
Water Disaster Risk in the Sendai Area
Sendai has low-lying and agricultural areas along the Sendai East Highway in its eastern regions, and some areas suffered tsunami damage during the 2011 Great East Japan Earthquake. The Hirose River and Natori River basins face flooding risks during heavy rains. Sendai's hazard maps are available on the city's official website, with flood, landslide, and tsunami maps publicly available. As of 2026, climate change continues to increase the frequency of heavy rainfall, so we recommend always checking Sendai's hazard map when selecting properties in suburban areas or near rivers.
Conclusion—Checking Hazard Maps Is Now Essential for Rental Property Selection
When choosing a rental property, checking a hazard map is no longer just "something good to do"—it's an essential preliminary investigation. Once water disasters occur, rebuilding life takes a long time. By adding the perspective of "Can I live here safely for a long time?" alongside affordability and convenience, you'll make rental property choices you won't regret in the future.
