The floods that hit Dublin and Wicklow resulted from 'monster rain' a phenomenon that is increasing in Europe, according to city council officials.
A council meeting heard this evening that much of Dublin's drainage infrastructure is 200 years old and could not cope with the amount of rain that fell.
Council executive manager Tom Leahy said further investment and planning controls will be required.
The use of porous surfaces on roads and driveways may be required in future developments.
He said that €120m had been spent on flood works in the city area over the past ten years and where works had been carried out such as the Liffey, Tolka and upper reaches of the Dodder, they held the water.
Mr Leahy also said there is no national flood warning system in this country.
Met Éireann had predicted between 40mm-70 mm of water over 24 hours, which was a level that had caused only localised flooding on 1 October.
There had been a severe weather alert on Sunday but he said these are issued every two weeks on average.
The city council said in the event over 100mm of rain fell in just a few hours.
The fire brigade received 774 emergency calls, while the drainage department received over 600. "Every switchboard was jammed" he said.
Defending the council's response, he said it was physically impossible to deliver sandbags to every house in an emergency.
He admitted that there had been a "malfunction" with the lock of floodgates on the Dodder and the fire brigade had to break padlocks to close them.
Meanwhile, City Manager John Tierney warned that funding for the Clontarf flood defences will be lost if a contract is not signed by the end of the year.
This evening councillors agreed to a further period of public consultation on proposals to lower the planned defences by around 45cm (1.5ft) on average.
Mr Leahy said most of the barriers consisted of grass mounds with walls only being used at four carparks.
He said only 400m of the 3,000m involved would obscure the sea view.
A final decision on the works estimated to cost nearly €10m will be made at the council's December meeting.
