There is no "quick fix" to prevent flooding which has hit some north Wales homes twice in under a year, the Environment Agency has said.
Many roads were closed or had speed restrictions
Some householders in the Conwy Valley have said they are facing financial ruin.
Many of those swamped by torrential rain at the weekend were made homeless after last February's floods.
The railway between Llandudno Junction and Blaenau Ffestiniog has been closed indefinitely because of flood damage.
A spokeswoman for Network Rail said the line would be closed "until further notice" and replacement buses were being put on.
Phil Jones, from Environment Agency Wales, said two of the biggest floods in living memory had happened in 11 months.
"We might not have another one for another 50 years - these are extreme events and they are rare," he said.
"We have been carrying out a computer model of the Conwy Valley and our defences within the valley.
Flooding in the Conwy Valley on Sunday
"We want to direct our resources and our energies towards defending the properties as best we can. Unfortunately there is no quick fix solution here."
Villagers saw their possessions destroyed on Saturday when the Conwy River burst its banks.
Many were hit by severe flooding last February and some had been back in their newly-refurbished homes just a few months.
Elizabeth Aylward, who lives in Trefriw, told BBC Radio Wales she expected the cost of repairing her property and replacing possessions to reach as much as £80,000.
"We had only really just settled back in, " she said.
"Last time, it cost about £80,000 to put right, and we are looking at about the same again. It's going to ruin us, basically."
Fellow villager Winston McCarthy had to have £34,000-worth of repairs done after last year's floods.
"We get the flood warnings, but what can you do?," he said.
Local MP Elfyn Llwyd said the situation was "heartbreaking and totally unacceptable".
He said he would be meeting Environment Minister Elliott Morley later this week.
"We will have to prioritise the Conwy Valley - it cannot happen again," he said.
"It happened in February, exactly the same thing again now. It simply is not on.
"Urgent attention is needed to deal with this matter so that we can alleviate this problem."
Environment Minister Carwyn Jones said his thoughts were with those who had been hit by the severe weather.
He said the assembly was doing all it could to help the Environment Agency and local authorities "to carry out the necessary work to prevent further misery as far as possible".