Is Your Home in a Landslide Warning Area? — How to Check, and the Warning Signs

When people think of disasters in Okinawa, typhoons come to mind first. But rain — whether from a typhoon or the rainy season — can cause slopes to collapse depending on how it falls.

Landslides differ from typhoons in one decisive way. A typhoon’s track is known days in advance from forecasts, but a landslide risk is determined by location. Whether it’s dangerous or not comes down almost entirely to where your home happens to be built.

So the first step in preparing isn’t shopping — it’s checking.

Check whether your home is in a warning area

Okinawa Prefecture states that you can check the approximate location of sediment disaster warning areas on a map.

Open the Okinawa Prefecture GIS (沖縄県地図情報システム — its menu is Japanese only), then follow:

「各種地図選択」＞「防災」＞「土砂災害危険箇所」 (“Select a Map” → “Disaster Prevention” → “Sediment Disaster Hazard Locations”)

to display it. Check your home, your parents’ home, your workplace, and your children’s school, one by one. It takes about 5 minutes.

But the map isn’t always up to date

Let’s be precise here. The prefecture states about its GIS:

Data on designated areas can take time to be reflected on the map, so the information shown may not always be current.

When you need confirmed information, don’t rely on the map — go to a public office. Warning area designations are published in the prefectural gazette, and the designation documents recording them can be viewed at the municipality where the area is located and at the prefecture’s civil engineering offices.

Civil engineering offices are divided by region.

When buying or renting a home, or if you can’t tell whether a property is in a warning area, don’t stop at the map — confirm with the municipality or the civil engineering office.

Warning signs before a slope gives way

Landslides can have warning signs. Okinawa Prefecture asks that if you spot one, you evacuate the area immediately and report it to the relevant authorities. The signs are organized by the type of failure.

Signs a debris flow is starting

• A rumbling sound from the mountain
• The river’s water level drops even though rain keeps falling
• The river’s flow turns muddy, or driftwood starts mixing in

Signs a landslide (slow slope failure) is starting

• Cracks appear in the ground
• Water in streams or wells turns muddy
• Water gushes out from the slope

Signs a steep-slope collapse is starting

• Water running off a cliff turns muddy
• Cracks appear in a cliff face
• Small stones start falling loose

If these are hard to remember, just keep three words in mind: “muddy,” “cracking,” “sound.” Of these, “the river’s water level drops even though rain keeps falling” is easy to miss precisely because it runs against intuition, and if you don’t already know about it, you’ll overlook it. It’s a sign that the flow is being dammed up somewhere upstream.

Landslides can also happen with no warning signs at all. The absence of a sign is not proof of safety. Judge together with how to read heavy rain information.

Evacuating works the opposite way from a typhoon

During a typhoon, the basic rule — after protecting your windows and balcony — is to stay inside, because going outside is the more dangerous option.

Landslides are different. Being in that location is itself the danger, so the judgment call is to leave. Even though both are “heavy rain,” the right action is the opposite depending on the cause — and that’s exactly where confusion sets in.

Okinawa Prefecture’s guidance for evacuation preparedness is as follows:

• Keep belongings to a minimum, carry them in a backpack rather than by hand, so both hands stay free
• Always move as a group with family or neighbors; avoid acting alone
• Turn off sources of fire such as electricity and gas, and lock up the house
• Everyone should help get elderly people, those with disabilities, and children to evacuate early

What to carry is covered in the emergency bag article (Japanese only); the difference between types of evacuation destinations is covered in Evacuation Sites and Shelters Are Different.

The prefecture recommends actually walking your evacuation route in advance. At night or in the rain, it looks like a completely different place from how it looks in daylight.

What to do ahead of time

1. Check your home, workplace, and school on the Okinawa Prefecture GIS (5 minutes)
2. If you’re in a warning area, confirm with the municipality or civil engineering office
3. Walk the route to your evacuation site once, in advance
4. Share the warning signs with your family (especially “the river’s water level drops”)

What this article does not cover

This site does not cover currently active landslide warning information or evacuation orders in effect right now. Always check official up-to-date information and announcements from your municipality.

Warning area designations change over time. Also, not being in a designated area does not mean “a landslide can’t happen here” — designation is one piece of evidence to judge by. This article does not evaluate the safety of any specific slope. For an individual assessment, consult your municipality or the prefecture’s civil engineering office.