SURFF - Operational flood warning system, Copenhagen

Multiple heavy rainfall events have struck the region of Copenhagen in 2010, 2011 and 2014. Particularly, in July 2011 Copenhagen experienced the worst rainfall ever resulting in damages and in a cost of around 1 billion €.

A modelling and management tool has been developed in order to minimize damages during stormy weather and the flooding created by these extreme events. The earlier the warning, the better protection of citizens, buildings and infrastructure is achieved. SURFF, Surface Flood Forecast, is an operational prediction tool based on hydraulic real-time simulations using 1D-2D model, numerical weather prediction nowcasts and radar nowcasts. 

Components installed in the solution

SURFF, it is a real time monitoring tool to control wastewater networks and treatment plants based on weather conditions. The SURFF System is structured as a number of modules which provides storage and quality control of time series data, activated the hydraulic simulation module and sends alerts to the users.

The necessary information which has to be available for the forecast of the flooded areas are: weather forecast provided from the local meteorological institute, measurement of seawater level, model of the city and of the pipe system. 

SURFF was developed by Veolia, through its Danish subsidiary Kruger. A project group consisting of Krüger A/S, the Danish Meteorological Institute (DMI) and the utility companies HOFOR, BIOFOS and Nordvand decided to develop an early warning system for urban flooding to support the deployment of standby and emergency services, and ultimately to inform citizens


Solution provider

Operational mode

SURFF is set up to provide flood warnings for 3 areas in Copenhagen. The project includes areas of high and low building density both combine and separate sewer systems.

The tool is based on weather prognosis and a terrain model combined with a model of the pipe flow. This online tool is able to warn about the risk of heavy rainfall 6 to 12 hours ahead. The system gives the local authorities enough time to implement the necessary security measures. The software switches the wastewater treatment plants to heavy rainfall mode, which temporarily increases their treatment capacity to avoid blockages and overflows.

The result of the SURFF is a map showing any forecasted flooding. This map is updated every hour and published on a website. The results may also be communicated through text messages, e-mail or social media.

After installing this tool, the number of wastewater overflows in Copenhagen decreased by 90% between 2013 and 2014. It also reduced the energy needed for wastewater treatment by 10-15% and the greenhouse gas emission by 10-12%.

The flood warning tool SURFF would be highly beneficial for most cities in order to protect themselves from the potential damages from flooding. Warning systems based on the combination of weather forecasts and hydraulic simulations are expected to yield the most accurate flood forecasts and are easiest to adapt if the urban water infrastructure changes.

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