The map draws its data from an automated monitoring network operated by Hanoi Sewerage and Drainage Company Limited (HSDC). It continuously updates rainfall measured in millimetres and flood‑water depth measured in metres, displaying the information on a colour‑coded map.

When users tap any point on the map, a pop‑up shows the location name, address, current rainfall and water depth. The app also lets users switch between street, light, dark and satellite views and search by address, street name or monitoring station.

The system can push proactive alerts to a phone even if the app is closed. Users may set the alert radius from 1 km up to 100 km around their position and choose the times of day when they want to receive notifications.

By providing instant, location‑specific flood data, the mini‑app helps residents avoid flooded roads, plan safer routes and reduce travel disruptions. It is especially useful for commuters, ride‑hailing drivers and delivery workers who need to adjust their journeys quickly during heavy rain.