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Scientists endeavour to better predict the locations and impact of floods

With a State of Emergency declared in both Saskatchewan and Manitoba this week, the flooding situation in those provinces has gone from bad to worse. The military has joined volunteers to set up sand bag barriers while countless homeowners build fortifications in advance of flooding — knowing full well their efforts may not be enough to hold back the rush of water.

According to Public Safety Canada , most floods in Canada are caused by winter snow runoff in spring. Rising temperatures can bring a quick melt of snow and ice, and ice jams and seasonal storms like we saw this week also contribute to the problem. Flooding remains the costliest of all natural disasters when it comes to property damage.

Hydrologists are saying the levels seen this past week in the overflowing rivers in central Canada are unprecedented, but it's not all that surprising considering the moisture-laden storms that have been rolling through and inadequate flood forecasting. And while heartbreaking scenes like we are seeing play out now are becoming all too familiar, science can try to help wage the battle against flooding.

We may not be able to stop Mother Nature, but we can use technology to help mitigate these disasters. Canada has been using Earth observation satellites to help in flood mitigation for years now.

Since 1995, the Canadian Space Agency has had at least one Radarsat satellite keeping a constant eye on the Earth, peering through clouds and the darkness with advanced radar.

Orbiting at an altitude of 800 km, the second generation Radarsat 2 is equipped with a powerful microwave instrument called a Synthetic Aperture Radar (SAR) which is able to see through clouds, smoke, haze and even night skies. And despite being in space, its electronic eye can see objects down to one metre is size.

With this kind of radar, data hydrologists can get a good idea of how rivers and streams ebb and flow with an eye toward flood control.

And because we know water follows gravity, scientists can measure the topography of flood prone regions and predict the path the rainfall will follow and know when local conditions might become unsafe.

In recent floods from Alberta to New Brunswick, Radarsat has been used to help assess the impact of flooding damage, predict the extent and duration of floodwaters, analyze the environmental impact of water diversion projects, and develop flood mitigation measures.

And while being able to follow up with reams of scientific data following a flood is valuable — how about predicting them months before they happen?

Now new research shows that we can look at subtle changes in Earth's gravity as an early flood warning system.

Hydrologists just published a new study in this week's issue of Nature Geoscience that analyzed data coming from NASA's twin Gravity Recovery and Climate Experiment (GRACE) satellites that show that a waterlogged river basin produces a stronger gravitational pull. Ground already saturated with water is prone to flooding by additional rains.

"These data can show us when river basins have been filling with water over several months,” said senior author Jay Famiglietti, a scientist at University of California at Irvine, in a press statement. “We’re not talking about actual flooding but about the saturation level of the ground and its predisposition to flooding. When it finally rains and the basin is full, there is nowhere else for the water to go.”

While detecting these gravity signals from space holds promise in making predictions out to a half year, this technique would still fall short in predicting flash floods caused by rainstorms — like in monsoon-linked floods in Pakistan or even the back-to-back summer storms that hit central Canada this year.

But a more immediate problem of using gravity measurements from the GRACE satellites is that it has very low resolution and it can take upwards of three months to get the data all streamed down — by which time it may be too late to put out a warning.

However, scientists have a plan, hoping to launch a follow-up mission to GRACE in 2017 that could download much higher-resolution flood warnings every two weeks.

This eye in the sky would be designed specifically to warn us of impending floods a full season before they hit.

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