Satellite images make it possible to monitor ice break-up in Torne River

SMHI has used high-resolution satellite images for the first time to monitor ice break-up in Torne River, one of Sweden’s largest unregulated rivers.

The CryoLand research project has developed a method of identifying ice jams in the Torne River and flooded areas around the river using high-resolution satellite images.

“Radar satellite images with a resolution of 1-3 metres can be used to distinguish between water and ice. They provide a good picture of where Torne River has open water and where it is covered in ice. If ice jams are formed during the ice break-up they can be seen, along with their size and how large an area is affected,” says David Gustafsson, a hydrology scientist at SMHI.

New monitoring opportunity with satellite

This year the ice break-up has been monitored in an area from the river delta and 40 km upstream on a level with Matkakoski.

“If a serious situation had developed with a lot of ice jams and flooding, we were on stand-by to use a type of emergency service whereby high-resolution satellite images can be ordered at short notice. The ice break-up has been very quiet since it began, so we have only used satellite images from regular passovers by radar satellite TerraSAR-X.”

“We hope that in future the images will be a natural part of the information material used by the warning service,” says Gustafsson.

Radarsatellitbild från TerraSAR-X den 6 maj 2013, islossning
Left, radar satellite image from TerraSAR-X on 6 May 2013, with preliminary results which show the Torne River and the large areas where the ice has already broken up (pink highlighting). Grey areas at sea and in Torne River’s wider section show areas covered in ice. The image to the right shows the area covered by TerraSAR-X on Google Earth. Source: CryoLand. Enlarge Image

Problems with ice jams in Torne River

Torne River is one of Sweden’s largest unregulated rivers. The ice is often thick and because the river varies in width it is not unusual for the ice to clump together on its way out to sea, forming ice jams in narrower passages.

The most serious problems arise when the sea ice outside of the river delta blocks the ice from the river. This can cause flooding in Haparanda-Tornio itself. However, ice jams further up the river can cause problems on their way down to the river mouth.