FAQ
How does potential differ from a forecast?
A forecast says how much rain is coming and where it will flood; potential says where the model floods if a given amount falls. There is no time in a potential map — it does not know whether tomorrow brings 350 mm. For live information see the WRA disaster site or the weather agency's heavy-rain advisories.
My cell has no colour — is it safe?
It means the modelled depth under that scenario is under 0.3 m, or the cell is outside the modelled area. The model ignores buildings, basements, thresholds and blocked drains, and assumes drainage works function. Try a larger scenario, and combine it with what you know about your lane.
Which of the ten scenarios should I look at?
No single answer. 350 mm in 24 h is roughly a typhoon or strong plum-rain day and makes a fair baseline; for "what would extreme look like" see 24 h 650 mm or 6 h 350 mm (short intense rain, the worst case for urban drains). Tapping the map lists all ten at once.
Why does everything look flooded when zoomed out?
Zoomed out, one screen pixel covers several cells and this site draws the deepest class among them, so it looks fatter than reality. From zoom 11 you see the original resolution.
Can I search a street address?
No. There is no free, licensed nationwide address geocoder; search by road, place or township instead, or tap the map or use your phone's location.
How often is the data updated?
The WRA reviews the maps every five years, sooner after major changes. This site uses the August 2022 third-generation national edition, stated on the data page; it is rebuilt when a new edition appears.
Can I use this to decide whether to buy a house or how much to insure?
The regulation says the data are for disaster prevention only and may not be a basis for land-use control or development restriction. This site shows the simulation and makes no further judgement.
What if the data is wrong?
The maps are made by the WRA and its river bureaus, the boundaries by the Ministry of the Interior; this site alters no cell. Report map issues to the WRA. Errors in this site's own processing (misaligned cells, wrong sums) are welcome here.
Back to the map · What a potential map is · Source & limits
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