HazardSim

Drop a tsunami, a meteor or 60 metres of ocean on any real coastal city. Real terrain elevation, real city boundaries, real population — see how far the water goes and who survives.

Ready

click a coastline to pick an area

water runs inland from the sea

Tsunami, sea level rise and meteor impact simulator on a real map

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.

What happens

Place

Clicking the map finds the city at that point and outlines its real boundary. The calculation runs on that area.

Wave height at the shore

m as tall as a 5-storey block

Population density

people per km² · log scale, up to 100,0004,000

Filled in automatically from OSM once you pick a city.

Aftermath

Killed—

Flooded—km²

Inland reach—km

Max depth—m

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.

City boundaries come from OpenStreetMap; terrain is Mapbox Terrain-RGB, real elevation at 10 to 30 m resolution. Water runs inland from the sea and floods everything below its level, losing 1 metre of height every 250 metres of travel — that stands in for friction against terrain and buildings. A hill, an embankment or a levee stops the wave for real. Hover the map after a run to read water depth and ground elevation. Sea level rise uses the same engine without the decay: the water simply sits at the given mark forever. The meteor is a body of stone, iron, ice or a loose rubble pile at the entry speed you set, 17 km/s by default, with damage radii from standard overpressure scaling and a crater roughly twenty times wider than the body itself. Casualties assume nobody evacuated; population comes from OSM or from the slider. These are orders of magnitude, not a forecast.

Click a coastline on the map, then hit Launch.