The damage and disruption caused by the recent storms is being discussed at a Welsh Government summit.
Representatives from councils, emergency services, businesses and voluntary groups are taking part.
First Minister Mark Drakeford has promised up to £10m for the 800 flood-hit homes and businesses.
However Rhondda Cynon Taf council believes more money will be needed, with the repair bill set to “run into millions and millions” of pounds.
Council leader Andrew Morgan said the number of properties affected was likely to be far greater than official figures say, with 800 affected in his local authority alone.
The Rhondda MP Chris Bryant called for people affected by floods in the area to be exempt from council tax.
There is a further warning of rain – including in south Wales, which saw most of the damage from Storm Dennis.
It will be in place from 15:00 GMT on Wednesday until 14:00 on Thursday.
There are five flood warnings in force in Wales, four of those in Monmouthshire, meaning flooding is expected and immediate action required. The fifth is in Llangollen, Denbighshire.
As cleaning-up continues, people are being warned not to risk their safety.
South Wales Fire and Rescue said some people had been using gas-powered heaters to dry out their flooded homes and businesses, which could cause carbon monoxide poisoning if not used correctly.
Water bottle stations were set up in Monmouth, after fears hundreds of homes could be left without supply after Welsh Water’s treatment site was flooded on Tuesday.
On Wednesday, engineers gained access to the Mayhill site to access the damage.
Managing director Peter Perry said engineers would be working “around the clock” to fix the damage but it could take up to 48 hours to get the plant up and running.
Announcing funding for flood victims on Tuesday, the first minister said he would consult councils to find the best way to assist both insured and uninsured residents.
Mr Drakeford said: “It’s going to be rough and ready because we want to do it quickly, and if you’re doing it quickly there’s bound to be a bit of rough justice in it.
“We’ve got a pretty good idea of the number of houses that were flooded across Wales. We’re looking to see the cut between those people who have got insurance and who haven’t got insurance.
“We hope to be able to offer some help to everybody because even if you’ve got insurance there is a delay in getting it and we want to be able to help families who need it now.”
He said more than 800 homes and businesses had been affected. However, not all the damage has been accounted for, and that figure is set to rise.
Mr Morgan called for a financial support package and raised concerns about potential job losses on the Treforest Industrial Estate where up to 400 businesses were affected.
“We also have to consider homelessness because some houses will not be able to be lived in for some time,” said Mr Morgan.
“That £10m is the initial amount for householders and businesses and we have released £1m from our own reserves. No doubt we will have to release more in the coming weeks.
“But the repair bill is going to run into millions and millions of pounds.”
He defended the council’s preparations ahead of the bad weather but admitted they had been “simply overwhelmed”.
The council is bringing extra staff with more rain forecast.
Mr Morgan added: “We’ve done as much as we possibly could, but we need to look at it again as these storms seem to be happening more frequently.”
The summit comes after Plaid Cymru accused the Welsh Government of not spending enough on flood defence.
Mr Drakeford accused Plaid leader Adam Price of trying to make “political capital out of misery”.
The first minister is being joined at the summit by Environment Minister Lesley Griffiths, Local Government Minister Julie James, and council leaders at the Welsh Government offices in Cardiff’s Cathays Park.
Natural Resources Wales (NRW), emergency services, the Federation of Small Businesses, Wales Council for Voluntary Action and trade union representatives are also taking part.
NRW said 163mm (6.5in) of rain had fallen in the 48 hours between lunchtime on Friday and Sunday and described the scale of flooding as “unprecedented”.
Chris Bryant estimated that a 100% council tax relief scheme for people hit by floods in Rhondda Cynon Taf would cost around £500,000.
“I think that in the end that bill should be paid by Westminster because this is one of the poorest communities in Britain,” he said.
The situation in Monmouthshire
Hundreds of properties, both residential and commercial, have been flooded, according to Monmouthshire council.
That has left several hundred people relocated or limited to living upstairs in their homes and a rest centre is in operation in Shire Hall, Monmouth.
Water levels on the River Usk remain high with standing flood water still posing a potential danger, the council said.
Tom Payne, of NRW, said it would be pumping water out of the town “24/7 for the next couple of days”.
The storms caused cancellations and delays with transport, and roads were blocked by floods and landslips.
A number of roads around Wales remain closed this morning because of flooding or landslips.
- In Monmouthshire, the A466 is closed between Wyesham and Llandogo
- In Powys, the A479 between the junctions with B4560 (Talgarth) and A40, as well as the A4077 Crickhowell Bridge
- The A4046 is shut between A467 (Aberbeeg Roundabout) and Railway Terrace (Cwm Roundabout) in Blaenau Gwent
- In Wrexham, the A525 both directions between B5426 (Bangor-on-Dee) and Pickhill Lane (Cross Lanes) Wrexham.
Train services are also being seriously affected with a number of lines closed due to track damage.
- Valley Line between Aberdare and Abercynon likely to be closed for a “number of days”
- Valley Line between Treherbert and Pontypridd to remain closed on Wednesday
- Ebbw Vale line closed following a landslip at Aberbeeg
- The Abergavenny to Hereford line
- Conwy Valley line closed with bus replacement service between Llandudno Junction and Blaenau Ffestiniog
Transport for Wales has also warned journeys may take “significantly longer” with bus replacement services also affected by flooding.
“The rail network is significantly damaged in places and with additional damage to roads and limited replacement road transport available to us, it’s inevitable that some services will be subject to disruption which will result in delays and cancellations,” said customer delivery director, Bethan Jelfs.
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