All data is extracted directly from an automatic monitoring station system managed and operated by Hanoi Sewerage and Drainage Company Limited. Rainfall is measured to the millimeter and water depth to the meter and updated continuously in real time, and the map uses a colour scale so users can see danger levels at a glance.

The flood map is embedded in the iHanoi app, which has 6.484 million registered accounts. Users can set an alert radius from 1 km to 100 km and schedule notification times. The app can send proactive alerts to phones without opening the app, helping residents choose safer routes and protect property.

When a flood appears inside the chosen radius, a pop‑up alert appears, allowing people to change their route, avoid submerged manholes or fast‑flowing water, and keep their vehicles safe. Office workers, students, ride‑hailing drivers, delivery staff and anyone travelling in the city can plan trips that steer clear of water, reducing damage and travel delays.

With location‑based, real‑time information, Hanoi’s flood map turns a potentially dangerous situation into a manageable one, letting millions of residents move around the city more safely during the rainy season.