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🌧️ Flood Risk Simulator

An illustrative flood-risk model: rainfall intensity and sea-level rise drive a simulated water level over a 48-hour rain event, compared against a flood-defense height, with a simplified exceedance-probability estimate.

Geology & Earth Science3DEasy60 FPS💧 Water 🌍 Earth

The Model (Simplified)

Water level = a small baseline level + a rainfall-driven surge that rises and falls over a simulated 48-hour rain event + a sea-level-rise offset. The surge peaks around hour 24 and its size scales with rainfall intensity, reduced by distance from the watercourse or coast. This is a teaching illustration, not a hydrological or hydraulic model — real flood forecasting uses river-gauge networks, terrain data and much more detailed physics.

Flood Defenses & Margin

The chart compares the simulated water level against a fixed flood-defense height (a wall, levee or raised bank). Where the water level exceeds the defense, the area is shaded red. The "margin" statistic is simply the defense height minus the peak water level — positive means the defense holds with room to spare, negative means it is overtopped.

Illustrative Exceedance Probability

The annual flood probability shown here is a simplified logistic curve of the margin, purely for illustration — real flood-risk mapping (such as a "1-in-100-year", or 1%, floodplain) is derived from decades of historical river and rainfall records combined with detailed hydrological models, not from a single simulated event.

About this simulation

This simulation is a deliberately simplified, illustrative model of flood risk — not a real hydrology tool. A simulated 48-hour rain event drives a water-level curve that rises with rainfall intensity, is pushed up further by sea-level rise, and is reduced the further you are from the watercourse or coastline. That level is compared against a fixed flood-defense height, and the area where water exceeds the defense is shaded red. A simplified logistic curve then converts the safety margin into an illustrative annual flood probability.

🔬 What it shows

A blue curve traces the simulated water level over 48 hours, rising to a peak around hour 24 as the modelled rain event intensifies then recedes. A dashed green line marks the fixed flood-defense height; wherever the blue curve rises above it, the region is shaded red, and a pulsing yellow dot marks the peak.

🎮 How to use

Increase Rainfall intensity or Sea-level rise to push the water level up, raise Defense height to add protection, and increase Distance from watercourse to reduce the effective surge reaching a property. The three presets contrast calm weather, a storm event, and a future scenario combining moderate rain with a large sea-level-rise offset.

💡 Did you know?

Climate change increases flood risk through several compounding mechanisms at once — warmer air holds more moisture, producing more intense rainfall events, while melting ice sheets and thermal expansion of seawater raise sea levels, meaning coastal defenses that comfortably held back storms decades ago are increasingly overtopped by the same size storm today.

Frequently asked questions

Is this a real flood forecasting tool?

No. It is a simplified, illustrative teaching model that captures the general shape of how rainfall, sea-level rise and distance affect flood risk, but it does not use real terrain data, river-gauge records or hydraulic modelling. Real flood-risk assessment (such as FEMA flood maps or UK Environment Agency flood zones) relies on decades of historical data and detailed physical models.

What does "distance from watercourse" actually change?

In this simplified model, distance reduces the surge that reaches a given point, following an exponential decay — representing the general real-world pattern that flood impact tends to lessen further from a river or coastline, though in reality local topography, drainage and flood defenses matter enormously and can override this simple relationship entirely.

Why does a "1-in-100-year" flood zone not mean it floods once a century?

A 1-in-100-year flood (or 1% annual exceedance probability) means there is a 1% chance of that flood level being reached or exceeded in any given year — not that it happens exactly once every 100 years. Over a 30-year mortgage, a property in a 1%-per-year flood zone actually has roughly a 26% cumulative chance of experiencing at least one such flood.

⚙ Under the hood

An illustrative flood-risk model: rainfall intensity and sea-level rise drive a simulated water level over a 48-hour rain event, compared against a flood-defense height.

flood riskclimate changesea level riseThree.jsflood defense

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install