By Miguel Pereira
COIMBRA, Portugal, Feb 11 (Reuters) - Part of Portugal's main motorway collapsed on Wednesday night after a levee broke underneath amid heavy rain and flooding that have been battering the country for weeks, as authorities evacuated about 3,000 residents in the northern area.
One of the levees on the River Mondego near the medieval city of Coimbra burst next to one of the pillars sustaining the A1 highway that connects the cities of Lisbon and Porto, causing a gap to form in the road that had been shut by police earlier, said Coimbra Mayor Ana Abrunhosa.
"Coimbra and surrounding towns have very serious problems due to floods, some are isolated... The situation is extremely unstable," she told national broadcaster RTP.
Prime Minister Luis Montenegro told reporters earlier authorities were "at the limit of our capacity to contain these waters".
A succession of deadly storms has hammered mostly central and southern parts of the country since late January, blowing roofs off houses, flooding several towns and leaving hundreds of thousands without electricity for days.
At least 15 people have died as a consequence of the storms, including indirect victims.
Montenegro was in Coimbra overseeing the emergency response after Interior Minister Maria Lucia Amaral resigned following criticism from opposition parties and local communities over what they described as the authorities' slow and failed response to devastating Storm Kristin two weeks ago.
As the storms let up this week, a weather phenomenon known as an "atmospheric river" - a wide corridor of concentrated water vapour carrying massive amounts of moisture from the tropics - brought new downpours, affecting the north to a greater extent.
RISK OF DAM OVERFLOWING
Municipal authorities in Coimbra ordered the precautionary evacuation late on Tuesday of around 3,000 people most at risk from the river bursting its banks. The operation was still under way on Wednesday, with police making door-to-door checks and bussing residents to shelters.
Regional Civil Protection official Carlos Tavares said the rain could cause the Aguieira dam, 35 km northeast of Coimbra, "to overflow, sweep away levees and trigger further flooding".
Portugal's environment agency APA expected an "exceptional period of peak flows" on the Mondego through Saturday.
Part of Coimbra's ancient city wall, on a hillside in one of Europe's oldest university towns and a UNESCO World Heritage Site, collapsed, shutting the road below and forcing the closure of the municipal market, the city hall said.
In central Portugal, just across the River Tagus from Lisbon, authorities evacuated the village of Porto Brandao due to the risk of landslides. Around 30 people were removed from their homes after a landslide in the neighbouring beachside area of Caparica.
(Additional reporting by Sergio Goncalves in Lisbon; writing by Andrei Khalip; Editing by Alex Richardson and Lincoln Feast.)
