Find out about the science and technology we use in flood detection and forecasting.
Our flood detection and forecasting service uses the latest science and technology. We are among the world leaders in this field. We currently provide flood forecasts for over 1000 places on our rivers and about 650 places around our coasts in England and Wales.
Considerations
There are many things that need to be considered when detecting and forecasting flooding. We have a wide range of rivers with different types of catchment areas. A river catchment is an area where water will collect and contribute to the flow of a river.
Some rivers respond very quickly to an increase in water level. These are usually found in upland areas and in towns and cities, such as Cumbria, Sheffield and London. Rivers that flow through larger and flatter areas can be found in more rural locations where the response to an increase in water level will be slower, for example like the Severn, Trent and Ouse.
Our industrial past also makes our river systems even more complex. Some of our major rivers, like the Thames, have locks and sluices that need to be taken into account in our forecasting models.
How do we detect where flooding may happen?
Our extensive network of rain and river gauges allows our flood forecasting officers to monitor weather and catchment conditions around the clock. The network consists of over 750 rain gauges, more than 1500 river level and river flow sensors and 100 coastal gauges, all of which transmit information via our Telemetry System. Every river level site can provide advanced warning of potential flooding.
How do we use rain gauges to measure rainfall?
Our rainfall telemetry sites are installed and maintained to high standards. Some of these sites are located in remote or harsh environments and need to work when the weather is at its worst.
We use tipping bucket rain gauges which are calibrated and validated regularly. This ensures that we have accurate rainfall information to use in the flood forecasting models.
Using RADAR to detect rainfall
Weather radar is used to monitor areas of rainfall that are moving towards or currently affecting a particular region. 
The UK radar network is jointly owned by the Environment Agency and the Met Office. We are working together to improve the accuracy, coverage and range of the radar and make it more user friendly.
A number of Met Office products can provide rainfall forecasts for up to 36 hours in advance. We use this information to forecast the water level in rivers.
There are 10 radar sites across England and Wales that provide radar coverage at three resolutions: 5km, 2km, 1km.
The most recent addition to the radar newtwork is at Thurnham, near Maidstone, and future developments will include the construction of two more radar sites in Bury-St-Edmunds and in Northumbria. We aim to complete these within the next two years. Building these new sites will extend radar coverage across East Anglia and the North East.
Our forecasting teams use the amount of rain forecast, the intensity of the rain and the area it will fall in our flood forecasting models. Radar images show precipitation movement, patterns and intensities and are helpful in learning how catchments react to certain rain profiles. These products are displayed on our HYRAD system as shown.
