Satellite Flood Prediction Could Save Lives

A powerful new tool to help predict devastating floods may prevent the deaths of thousands.

By Michael Reilly | Fri Nov 13, 2009 02:45 PM ET

A house is pounded by flood waves.
Getty Images

Floods are among the most common natural disasters on the planet. Over one billion people are at risk, and thousands of people die in floods each year. Those numbers are projected to climb as the effects of global warming speeds up the water cycle, causing more extreme storms, rainfall and flooding.

However, a powerful new tool that uses satellite measurements that track the amount of water coursing on and beneath Earth's surface could help scientists predict devastating floods.

WATCH VIDEO: Predicting the height of a flood in important when lives are at stake.

Flood forecasting is full of uncertainty -- more art than science. Current methods rely on a compilation of recent rainfall figures coupled with surveys of local landowners and authorities, often drawing conclusions based on the inexact question: "How wet is the ground where you are?"

The Gravity Recovery and Climate Experiment (GRACE) satellite is changing all that. GRACE measures fluctuations in Earth's gravitational field as water mass courses around the planet's surface and seeps through its soils, providing the first concrete tally of how wet or dry a region really is.

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J.T. Reager and James Famiglietti of the University of California, Irvine found that amid all the sloshing about, a reliable yearly cycle of groundwater water storage emerged in most regions around the world.

For example, in Africa's Niger River Basin, water levels quickly rose from an annual low of just a few inches stored in soils up to around 30 centimeters (1 foot) of water in early spring. After that, the land could hold no more. Any additional rains would swell the mighty Niger, the third-longest river in Africa after the Congo and Nile, and cause flooding.

"We see certain areas of the Earth becoming swollen with water mass, and we have to assume that there will be a point where these ecosystems cannot hold any more water," Reager said. "This is our tip off that flooding may soon occur in these places."

When the researchers compared GRACE data from 2003 through 2008 to known floods during the same time period, they matched up well. The researchers are hopeful that their new method could dramatically improve flood prediction times, allowing authorities to issue an advisory that there is a high risk of flooding up to a month in advance of any disaster.

Their work is due to be published in the journal Geophysical Research Letters.

"You can use GRACE to say that water storage is reaching a maximum capacity," Matthew Rodell of NASA's Goddard Spaceflight Center in Greenbelt, Md., said. "It has a nice predictive capability for flooding."

Rodell was not involved in the study, but added that he is working on using GRACE measurements for predicting and monitoring droughts.