Flooding and landslides from heavy rain have become some of the most frequent and deadly disasters in Japan. Intense, concentrated downpours can overwhelm rivers and drains in hours. The good news is that floods, unlike earthquakes, usually come with warning — which means preparation and timely evacuation can save your life. The key is knowing your risk before the rain starts.
Why it's getting worse: 線状降水帯
A growing threat is the 線状降水帯 (senjō kōsuitai, "linear rain band") — a line of thunderstorms that forms and stalls over the same area, dumping enormous amounts of rain for hours. These bands can cause sudden, severe flooding and landslides, and the Japan Meteorological Agency now issues specific alerts when one is detected or likely. Treat any 線状降水帯 warning as extremely serious.
Check your hazard map today
The single most important thing you can do is find out whether you live in a flood- or landslide-prone area — before it ever rains hard. Use the national hazard map portal:
- ハザードマップポータルサイト — the government's hazard map portal at disaportal.gsi.go.jp. Enter your address to see expected flood depth, landslide-risk zones, and storm-surge areas.
- Note the predicted flood depth for your home and identify a safe higher location you could move to.
- Locate your nearest evacuation site — see our evacuation shelter guide for how to find and use it.
Understand the 5 warning levels
Japan uses a standardized 5-level warning scale (警戒レベル) for floods and landslides. Know what each level means so you act at the right moment:
- Level 1–2: Stay aware, check forecasts, and review your evacuation plan.
- Level 3 — 高齢者等避難 (evacuation of the elderly etc.): Older people, those with disabilities, and anyone who needs more time should evacuate now. Everyone else should prepare to leave.
- Level 4 — 避難指示 (evacuation order): Everyone in the area must evacuate immediately. Do not wait for Level 5.
- Level 5 — 緊急安全確保 (emergency safety measures): A disaster is already occurring or imminent and safe evacuation may no longer be possible. Take the safest action you can right now — move to the highest floor and away from the water.
If you live on the ground floor
- Move valuables, electronics, and important documents up high as soon as heavy rain is forecast.
- Evacuate upward and outward early. Ground-floor and basement spaces flood first and fastest. When a Level 4 order comes, leave for a shelter or higher ground while roads are still passable.
If you live on an upper floor
- "Vertical evacuation" may be safest. If your building is sturdy and you are well above the predicted flood depth, staying put on a high floor (在宅避難) can be safer than wading out into rising water.
- Stock up in advance. If you shelter in place, you may lose power and water for days. Keep food, water, and a charged power bank ready — see our power outage guide.
Protect your documents
Keep your 在留カード (residence card), passport, insurance certificates, and bank information in a waterproof pouch you can grab in seconds. Replacing water-damaged documents is slow and stressful.
Waterproof document pouch
Keep your 在留カード, passport, and key papers dry and ready to grab during an evacuation.
Find waterproof document pouches on Amazon →Sandbags (土のう)
Sandbags or water-absorbing flood bags placed at doorways can slow water from entering a ground-floor home.
Find sandbags on Amazon →Rubber boots and waterproof flashlight
Tall rubber boots and a waterproof flashlight help you move safely if you must evacuate through wet, dark conditions.
Find boots and waterproof flashlights on Amazon →After the water rises
- Never walk or drive through floodwater. Just 30 cm of moving water can sweep you off your feet, and you cannot see open manholes, ditches, or debris beneath the surface. Driving into flooded roads is a leading cause of flood deaths.
- Watch for landslides in hilly areas — they can occur during and even after the rain stops.
- Report and photograph damage to your home for insurance and for the municipal damage certificate (罹災証明書) you may need for support.