Direct rail services between north and south Wales could be cancelled for more than a week due to flood damage.
Network Rail said flash floods washed away parts of the track at Pontrilas, Herefordshire, affecting services between Hereford and Abergavenny.
Some roads remain shut and there are flood warnings in places across Wales.
The Met Office said more than 4in (100mm) of rain fell in 24 hours in some places.
Emergency crews rescued people from cars stuck in floods and people were evacuated from homes on Saturday.
About 25 homes were evacuated in Skenfrith, Monmouthshire, following flooding and a power cut, according to South Wales Fire and Rescue Service.
People were also evacuated from Monmouth Caravan Park while the council's emergency response staff deployed sand bags through the night.
Teams from South Wales Fire and Rescue Service were also on hand in the town to help families who found roads blocked by flood water.
Monmouthshire council leader Peter Fox said the authority was hoping the situation would improve given the immediate danger had passed.
"I would like to send my thoughts to residents and businesses impacted by the flooding," he added.
"Nobody ever wants to be forced from their home but in these circumstances I'm glad we are able to help.
People were also rescued by firefighters from seven properties at Mill Green near the River Teme in Knighton, Powys, where several roads remain blocked, as in other areas.
There are no direct trains between north and south Wales with the line out at Pontrilas, Herefordshire.
No trains will run between Hereford and Abergavenny due to several sections of track, ballast and embankment being eroded or washed away.
The line is expected to remain closed until Monday 4 November, according to Network Rail.
"We understand how disruptive the closure of the Marches line will be to passengers and we'll work as fast as we can to get it back up and running again," said a spokesperson.
Flooding has also led to line closures between Shrewsbury and Welshpool.
The Cambrian and Heart of Wales lines have been hit with Transport for Wales (TfW) advising people to check journeys before travelling.
Heart of Wales services are terminating at Llanwrtyd Wells and Llandrindod Wells coming from Swansea direction, and the Fishguard Harbour line has also been affected.