Satellites help find reasons for floods

Prague was one of the cities hit by recent floods

Scientists can now monitor river levels globally by satellite, helping them see if floods like those recently seen in Europe are due to climate change, or if they are a one-off disaster.

A computer programme devised by researchers at Leicester's De Montfort University could also help predict how global warming will change the world's climate.

Satellites measure the height of the sea by timing how long it takes a beam to bounce back.

But for rivers the beam is too wide - and there is interference from echoes either side. This has meant it has been impossible to make accurate predictions from the data recorded over land.

Satellite images of the Amazon - red areas show where it is deepest

Now, the De Montfort researchers have been able to filter out the interference and monitor the world's lakes and rivers.

The programme uses data collected by satellites over the last 10 years using an instrument called a radar altimeter.

The De Montfort team studied patterns in the land readings and found a way to recognise similar shapes.

Using these, they devised a computer system which can interpret the data collected over rivers and lakes.

It means climate experts can track river level changes due to global warming, and could help predict areas at high risk of flooding.

Predicting floods

In a separate development, the European Space Agency sent images from its satellites to Switzerland, Austria and Germany of areas at risk during the recent floods.

These satellites take detailed images of specific areas, so experts were able to see if different parts of a river were affected. The technology may also help them be better prepared in the future.

Dr Urs Frei of the remote sensing laboratories at the University of Zurich, said: "The elevation model could help to simulate different scenarios - which areas would be flooded depending on water level."

This data will be particularly useful for rivers in remote areas

Professor Philippa Berry, De Montfort University

The scientists from De Montfort University say their programme can help on a more global scale.

Philippa Berry, professor of geomatics in the school of computer sciences at the university told BBC News Online: "We realised we kept seeing the same kind of echo shapes occurring, so we built up a library. We gradually developed this fully automated system."

One of their first rivers they have tracked is the Amazon. Researches have been able to show the water flowing off the Andes, down into the tributaries into the river and eventually to the sea.

Climate information

Professor Berry said: "The 10 year time series will allow climatologists to discriminate between events that are a result of climate change, or that are a one-off occasion."

She added: "We are starting with the major rivers because they are most important for climate experts, Then we will move to smaller rivers.

"This data will be particularly useful for rivers in remote areas , such as the Amazon or the Congo."