Firemen are desperately trying to pump the water back into the River Rhone just by the bridge at Arles.
The river is extremely fast-flowing and it is just about one metre below its highest point where it would flood the entire city.
Roads in Provence have simply vanished
On Wednesday night it did burst its banks. The firemen here are wading up to it in about a foot or so of water and hundreds of people living by the river in Arles have had to be evacuated.
Fire chief Denis Perrier says it has been a tough fight:
"Our main task has been to protect the old quarter of Arles because some of the town has been built at a lower level than the river and the water has risen fast to 13,000 cubic metres per second.
"So we had to try and protect the people and their homes."
As the firemen do their job, a group of people are standing here looking at the level of the River Rhone, among them a group of teachers.
School has been shut for the past few days and most of them have been evacuated from their own homes next to this swollen river.
We drove from Arles to Avignon, normally a half-an-hour journey - it took us three and a half hours.
Almost all the small roads are blocked. Even the main roads are blocked and the tail-backs last for miles.
France's great mediaeval cities are at risk
Now Avignon, another ancient city here in the south of France, has also suffered from the Rhone bursting its banks.
Where I am standing now is normally a car park and a bus station but there are no cars and no buses - it is simply a sea of mud.
And by the river, which is also swollen to unusually high levels here, people are simply standing and looking in amazement and hoping that it does not get any higher.
"People in the small villages were all inundated with water inside their houses and that's crazy," said one woman.
A man added that the university had been closed because the rain meant the roads were impassable.
Avignon is not the only place now having to get rid of the swathes of mud and debris and wait for the waters to go down.
Across the south of France, 37,000 homes have been left without electricity. Many of the worst affected areas are still completely cut off.
A quarter of a million people are without drinking water and still the rivers remain at dangerously high levels even though the rains now seem to have stopped.
Many here are blaming the authorities for allowing homes to be built too near the flood plains - others shrug their shoulders and say it is simply global warming and there is not much they, here in France, believe they can do about that.