How it works
Flood Check puts satellite data, weather data and map data together in one model. The model moves the rain across the ground, hour by hour, for 60 m squares across the city. Everything in it comes from public data. It replays two floods: Lagos, 28 June to 1 July 2026, and Nairobi, 5 to 8 March 2026.
What goes into the model
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Rain
Hourly rain from a global weather model, for each hour of the four days, at twelve points across each city. Weather models spread a storm out and make it weaker, so the rain is scaled up to match a rain gauge reading from an earlier Lagos storm. The same scale is used for Nairobi, where no gauge reading has been checked yet.
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Ground heights
A satellite height map of the land at 30 m. It also measures roofs and trees, so a filter removes them to find the ground. The heights then go onto 60 m squares, and the low, connected water at the edge becomes the lagoon and the sea.
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Lagoon and tide
In Lagos, the lagoon level goes up and down with the tide. When the lagoon is high, water near the shore cannot drain into it. The Lagos environment commissioner gave this as the cause of the June flood. Nairobi is inland, at about 1,600 m, so it has no lagoon or tide.
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Drains
Each square drains away a fixed amount of water each hour. The drains work less as the ground gets near the lagoon level, and stop below it. The canals and drains people have put on the map show on the depth card. In Nairobi the model has no river channels: water that reaches a valley stays there until it spreads or drains, so the depths along the Nairobi, Mathare and Ngong rivers are higher than the real water was, while the pattern matches the reports.
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How the water moves
The model cuts each hour into 30 small steps. In each step, rain falls, drains take some away, and water flows from each square to its lower neighbours. The map shows the result for every hour.
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Buildings and their heights
Building outlines from the open map, plus buildings that satellite image analysis found and the map lacks. Each building gets a height from the map when someone recorded one, else from a satellite estimate. "Water at the door" counts the buildings with 10 cm of water or more next to them.
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Roads, walls and place names
From the open map. A road turns red where the water is 10 cm or more, and deep red from 30 cm, where most cars stop.
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Trees
Tree heights for every 10 m square, measured from satellite data. A tree stands wherever the trees are 5 m tall or more, and no building or water covers the square.
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Satellite imagery
A cloud-free picture of the ground made from many satellite passes, laid under the buildings and the water.
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Press reports
What the newspapers reported, pinned at the places they named, from the hour each report is about. Each one shows what the model has at that place.
How we check it
We compare the model with the press reports of this flood, with past flood reports from the news, and with answers from people who were there ("Did it flood here?" on the depth card).
It is a model, not a measurement. It shows the pattern of the flood. A 60 m square can hold a high plot next to a low road, and blocked drains are not in the model.
Credits
Rain: ECMWF IFS through Open-Meteo (CC BY 4.0). Ground heights: Copernicus DEM GLO-30, produced using Copernicus WorldDEM-30 © DLR e.V. 2010-2014 and © Airbus Defence and Space GmbH 2014-2018, provided under COPERNICUS by the European Union and ESA. Imagery: Sentinel-2 cloudless 2024 by EOX IT Services GmbH, contains modified Copernicus Sentinel data 2024 (CC BY-NC-SA 4.0). Map data: © OpenStreetMap contributors (ODbL). More buildings: Google Open Buildings and Microsoft ML Buildings through Overture Maps. Building heights: Google Open Buildings 2.5D Temporal 2023 (CC BY 4.0). Trees: ETH Global Canopy Height 2020, Lang et al. 2023 (CC BY 4.0). Press reports: Vanguard (Lagos), Citizen Digital and Kenyans.co.ke (Nairobi). Search: Photon by Komoot.
Dataset links and model details
Questions
When did the Lagos flood happen?
Rain fell over Lagos from Sunday 28 June to Wednesday 1 July 2026. In the model, the most land was under water at 17:00 on Tuesday 30 June, after more than 12 hours of rain.
Which parts of Lagos flooded?
Press reports named the Lekki-Epe Expressway, Jakande in Lekki, Victoria Island, Ago Palace Way in Okota, Ikorodu Road at Maryland, Oshodi, Gbagada, Mafoluku, Oyingbo and Iwaya in Yaba, among others. The map shows each report at the place it names, from the day it is about.
What happened in Nairobi?
Heavy rain fell on the evening of Friday 6 March 2026. The Nairobi, Mathare and Ngong rivers burst their banks, and roads in the CBD and on Uhuru Highway, Mombasa Road, Thika Road and Jogoo Road flooded. Police reported 10 deaths the next morning. In the model, the most land was under water at 01:00 on Saturday 7 March. Switch to Nairobi at the top of the map.
How deep was the water on my street?
Search your street on the map. A card shows the modelled depth there for every hour of the four days, the highest water, the hours over 10 cm, the roads near you under water and the nearest mapped drain.
Why did Lagos flood?
The Lagos environment commissioner said heavy rain fell at the same time as high sea level, so stormwater could not drain into the lagoon. The model shows this: low ground near the lagoon drains slowly when the tide is high.
Is this a measurement of the flood?
No. The depths come from a simple model on public rain, ground height and lagoon data, on 60 m squares. They show the pattern of the flood, not exact depths at a door. No public satellite flood map of this event exists.
Is Flood Check free?
Yes. It is free, needs no account, and sets no cookies. It counts anonymous usage only.
The depths come from a simple model. They show the pattern of the flood, not exact measurements. Use them as a guide.