A dam partially burst on Wednesday following days of heavy rain that triggered landslides and flooding in mountainous southern Norway, a police official said. Communities downstream already had been evacuated.

The Glomma, Norway’s longest and most voluminous river, is dammed at the Braskereidfoss hydroelectric power plant, which was under water and out of operation.

Authorities initially considered blowing up part of the dam to prevent communities from getting deluged. But the idea was scrapped since water later broke through the dam, police spokesman Fredrik Thomson told reporters.

“We hope that we will get a gradual leveling of the water and that we will get an even leveling,” he said.

Huge volumes of water were pouring over the western parts of the dam, Thomson said.

“The water has gradually begun to seep through the side of the dam, and as of now it is not appropriate to take any measures at the power plant,” Thomson said, adding that the situation is being assessed continuously.

At least 1,000 people live in communities close to the river in the area, and authorities said that all had been evacuated before the dam partially burst.

Hatches in the hydroelectric power plant failed to open automatically as they are supposed to when there is more water in the dam, according to Alexandra Bech Gjorv, chair of the board at operator Hafslund Eco. The reasons for the failure are unknown, she said.

Separately, a Norwegian woman in her 70s died early Wednesday after falling into a stream the day before. She managed to crawl up onto the banks, but because of the floods, it took several hours before rescue teams could take her to the hospital, where she died, police said.

Police in southern Norway said more than 600 people were evacuated in a region north of Oslo overnight and said the situation there was “unclear and chaotic.” The Norwegian Public Roads Administration said Wednesday that all main roads between Oslo and Trondheim, Norway’s third-largest city, were closed.

“We are in a crisis situation of national dimensions,” Innlandet country Mayor Aud Hove said. “People are isolated in several local communities, and the emergency services risk not being able to reach people who need help.”

Storm Hans has battered parts of Scandinavia and the Baltics for several days, causing rivers to overflow, damaging roads and injuring people with falling branches.

More heavy rain was expected over southern Norway and central Sweden Wednesday, as sheds, small houses and mobile homes floated in rivers or were carried away by strong currents.

Norwegian meteorologists said that up to 30 millimeters (1.2 inches) of rain could be expected by Wednesday evening, saying “the quantities are not extreme, but given the conditions in the area, the consequences may be.”

In Goteborg, Sweden’s second-largest city, large parts of the harbor were under water.

The meteorological institutes for both countries issued extreme weather warnings Wednesday.

“This is a very serious situation that can lead to extensive consequences and damage,” the Norwegian Meteorological Institute said. Its Swedish counterpart issued a red warning for the west coast, saying “very large amounts of rain causing extremely high flows in streams” could be expected. 

Erik Hojgard-Olsen, a meteorologist with the Swedish Meteorological and Hydrological Institute, was quoted as saying by the Aftonbladet newspaper that the weather was unusual for this time of year.

“It is exceptional to have such a low pressure (system) as Hans, which has brought so much rain for several days in a row,” he said. “Especially for being a summer month, it has lasted a long time.”

The Norwegian Water Resources and Energy Directorate upgraded its warning for floods and landslides from orange to red for parts of southern Norway. The directorate said record-high flood levels were recorded in several places in the Drammensvassdraget, a drainage basin west of Oslo, the capital.

Erik Holmqvist, a senior engineer at the agency, said four lakes, including the Randsfjorden, the fourth-largest in Norway, were particularly vulnerable to flooding.

“We have to go all the way back to 1910 to get the same forecasts for the Randsfjorden,” Holmqvist told the VG newspaper.

Norwegian Prime Minister Jonas Gahr Store visited the affected areas of southern Norway. “When the rain stops, another challenge begins: the water needs to get out,” he said.
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