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A road to the world-famous Icelandic attraction was also damaged, as a nearby volcano erupted for the seventh time in less than a year.
Official Giorgi Kalandarishvili was doused during the confirmation of a controversial poll.
The man and four children, including his daughter, were trapped inside at a English language school.
Video shows people in Calle Alcazabilla struggling to cross a road as flood water surges through it.
A general election in the Republic of Ireland has officially been called for Friday 29 November.
People are angry at the authorities' handling of floods which killed more than 200 people.
There were no immediate reports of casualties after heavy rain on Thursday.
Video shows a flooded terminal inside El Prat airport and partially submerged cars on a highway.
As anger flared in the stricken town of Paiporta, the Queen of Spain, with mud smeared on her face, was seen crying.
The BBC's Mark Lowen in Paiporta: "People are picking up mud, throwing it at the king"
Spain's King Felipe VI is visiting the Valencia region, which has been hit by unprecedented floods.
There has been a growing outpouring of solidarity in and around Valencia to help those affected by catastrophic flooding.
Several people have died, with dozens of rescue workers searching for survivors under the rubble.
Cars were still driving along streets when the Valencian town of Paiporta was hit by devastating floods.
The BBC's Nicky Schiller says the La Torre area of the city has been completely devastated.
The BBC has visited Paiporta, Valencia, where dozens of people have been confirmed dead.
At least 158 people were killed following flash floods in southern Spain.
The BBC's Nicky Schiller reports from the scene of Spanish flooding where cars are piled up.
At least 95 people have died and more are missing after torrential rain caused devastating flash floods.
