Click any coastline and the city under your cursor is outlined by its real boundary, which becomes the calculation area. Elevation data is real, so water flows around hills and fills the low ground.
Population density
people per km² · log scale, up to 100,0004,000
Filled in automatically from OSM once you pick a city.
How this is calculated
Are these numbers real?
The terrain is. Elevation comes from Mapbox Terrain-RGB at 10–30 m resolution, city boundaries from OpenStreetMap, population from OSM tags. The physics is deliberately simple: water floods everything below its level and loses height as it travels, blast radii use standard overpressure scaling. Treat the result as an order of magnitude, not a forecast.
Can this predict a real tsunami?
No. A real tsunami depends on the shape of the seafloor, the fault that moved, the tide and the hour of day. This tool answers a different question: if water of a given height arrived here, how far inland would the terrain let it go, and who lives there. Casualty figures assume nobody evacuated, which never happens in reality.
Why can't I pick an inland city?
Tsunamis and sea level rise need a coast. Before calculating, the site checks for open sea within about 30 km of your point, using the same elevation data. Meteors have no such limit — you can drop one anywhere on Earth.