The blocked drains on a Northampton street 'were not the difference' that led to a flashflood damaging dozens of homes and businesses last year.
In May 2018, filthy floodwater poured into the homes, businesses and takeaways of St Leonard's road when a sudden thunderstorm unleashed a month's worth of rain in two hours.
Now, a report says although blocked drains made the floods worse, it would have happened 'regardless' as the street's drains were not fit to handle the sudden downpour.
The report - which was commissioned by Northamptonshire County Council as the lead local flood authority - also suggests bin bags left out for collection the night before were swept along in the flood water and partially blocked drains.
It comes after the Chronicle & Echo reported in July 2018 that some drains in St Leonard's had not been cleaned in two years.
Pictures of the drains after the floods showed them packed with silt and mud. The Chron videoed contractors working on their hands and knees with crowbars to remove the built-up silt.
The report reads: "Even in a fully cleansed condition, the system of private drainage, road gullies and public sewers throughout the catchment ... would have been at capacity and ineffective very soon after the start of the storm.
"The flood incident was a result of an exceedance event with rainfall in excess of design capacity of drainage systems. The extent and peak depth of flooding would have occurred regardless of the state of maintenance of drainage systems."
The report reveals how fire and rescue services received over 160 emergency calls in Northampton at the time of the flood.
St Leonard's could have been hit by over 64mm of rainfall, but because of the street's natural 'bowl' shape surface water collected and reached a depth of up to 900mm in places.
At least 73 properties in St Leonards, Euston Road, Towcester Road and Alton Street were flooded, but there could have been more.
Councillor Ian Morris, county council cabinet member for transport, highways and environment, said: “This is important so that lessons can be learned to try and minimise the risk of this sort of thing happening again.
“What we have discovered here though is that this was a freak storm that deposited up to twice the monthly rainfall over the period of one hour and very little, if anything, could have been done to prevent it."