Hazard Maps (Hazado Mappu) in Japan
A hazard map in Japan answers one question before any storm does: what does water, slope, or sea do at your exact address.1 Every municipality publishes ハザードマップ (hazādo mappu, "hazard maps") showing risk zones plus evacuation centers, and the national 重ねるハザードマップ (kasaneru hazādo mappu, "overlay hazard map") portal stacks those zones on one searchable screen.2 Check your address early in tenure, reassess on every move, and let the result set your evacuation timing.
Procedures, fees, and requirements can change. Confirm current details at the MLIT hazard map portal and your municipal disaster-prevention page.
Overview
Municipal maps show flood-risk, landslide-risk, tsunami, and surge zones with shelter locations; the MLIT portal aggregates municipal data into a national address search with an English UI.23 Map colors encode expected 浸水深 (shinsui-shin, "inundation depth"), and companion layers add flood duration and building-collapse zones.4 Your band on that map is the single most important typhoon, flood, and earthquake-evacuation decision input you own.
Two Map Layers
Your municipality's map
Under Flood Control Act Article 15-3, municipalities covering an inundation zone must produce flood hazard maps showing zones, depths, and evacuation information, and distribute them to every household.1 Distribution runs through print and the web, and new arrivals can request their copy at the municipal office.1 The municipal map governs locally: its shelter list and district notes override anything a national screen suggests.
The MLIT Kasaneru portal
The portal's overlay map stacks flood, landslide, surge, tsunami, road, and land-character data on one screen for any address in Japan.2 Search by address or postal code, toggle layers, and read the color at your point.2 An English UI is available through the MLIT disaster portal language set, alongside Japanese and other languages.23 The companion わがまちハザードマップ (wagamachi hazādo mappu, "my-town hazard map") side links each address out to its municipality's own published map.2
Using the Kasaneru Portal
Enter the property address or postal code first, not the nearest station name; the station location is not your risk.2 Toggle flood layers for each nearby river at both modeled scales: the planned scale and the maximum-anticipated scale of roughly once-in-a-thousand-years rainfall.1 Then toggle landslide, surge, and tsunami layers even when the flood color looks calm; hillside and coastal addresses carry risks the flood color hides.2 Save or print the result with the address visible, and repeat the lookup for any new address before signing a lease.
Reading Inundation Bands
Municipal maps commonly band expected depth as under 0.5 m, 0.5 to 1 m, 1 to 3 m, 3 to 5 m, and 5 m plus, darkest for deepest.5 The table below states what each band demands of residents.
| Band | Water behavior | Resident consequence |
|---|---|---|
| Under 0.5 m | Ankle-level flooding | Furnishings and electrics at risk; evacuation strongly advised for ground floors |
| 0.5 to 1 m | Knee-to-waist height | Ground floor unusable; move valuables and sleep upstairs |
| 1 to 3 m | First floor floods | First floor fully flooded; upper-floor shelter or evacuation |
| 3 to 5 m | Upper floors reachable | First floor destroyed; evacuate unless building is tall and stocked |
| 5 m plus | Whole-house submersion | Extreme danger; leave at the earliest advisory |
The bands above follow commonly published municipal practice.5 Depth defines the concept; the official manuals fix zone types and measurement rules rather than one universal palette.4
Duration and building-collapse zones
Duration layers show how long water stays at 0.5 m or deeper; a long duration rules out waiting it out upstairs without supplies.14 家屋倒壊等氾濫想定区域 (kaoku-tōkai-tō-hanran-sōtei-kuiki, "building-collapse flood zones") mark where fast breach flows or bank erosion can destroy wooden houses.4 Inside a collapse zone, vertical evacuation at home is unsafe regardless of depth band.1
A shallow color inside a building-collapse zone still means leave. Flow destroys houses that depth alone would spare.4
Your Address as the Decision Input
High-band addresses evacuate at Level 3
Residents in deep-band or collapse-zone addresses should treat evacuation Level 3 as their leave trigger.6 Roads flood before rivers peak, so the early trigger buys the only safe travel window. Tell the household the trigger address by address, not city by city.
Low-band addresses may shelter through Level 4
Outside collapse zones with shallow bands, upper-floor sheltering is an allowed option at Levels 3 and 4, conditioned on confirming depth, duration, supplies, and isolation tolerance.6 Confirm each condition explicitly: depth under the floor you sleep on, duration shorter than your supplies, no collapse-zone overlay, and a charged phone with the municipal channel on.
Check Early, Recheck on Every Move
Check the map in the first weeks of tenure, when address registration brings you to the municipal office anyway.1 Recheck on every relocation, since bands change street by street and a station-area move can shift depth by meters. Renters should run the lookup before signing, not after moving in; the map result is a legitimate input to the accept-or-reject call.
Good to know
No color does not mean no risk
Zones model specific rivers at specific rainfall; unmodeled tributaries, heavier-than-modeled rain, and drainage overload still flood outside them.4 Treat white space as unmodeled, not as safe.
Maps assume the modeled rainfall, not heavier
Maximum-anticipated modeling can still be exceeded by real storms.1 Read bands as floors for planning, not ceilings on what water can do.
Landslide and surge layers matter as much as flood
A calm flood color with a red landslide overlay is a dangerous address in a typhoon.2 Toggle every layer that applies to the terrain around the address, every time.
See also
- Fire Insurance and the Carrier-Substitution Trick
- Move-In Day Checklist
- Property-Search Portals: SUUMO, HOME'S, athome and Their Quirks
- What to Do During an Earthquake