Hundreds of Redbridge homes are in danger of being flooded with sewage if a project to control the River Roding is not funded.
A catastrophic flood in 2000 turned the Charlie Brown roundabout into a lake and inundated around 400 homes, causing damage that cost tens of thousands of pounds to repair.
Rising waters caused sewage to back up through the drains into people’s homes.
Cllr Linda Hugget (Con, Monkhams) was one of those hit by the “horrendous” flood two decades ago and damage to her home took about a year to repair at a cost of £20,000.
She said: “It was not water that came through the drains, it was sewage.
“You can’t even begin to describe the smell, it was like having an open sewer running through your house.
“A lot of those properties were not insured the last time round. For many that were affected it was probably the most horrendous experience one could wish for.”
The Environment Agency has warned that, due to the effects of climate change, the river could pose a threat to 2,600 homes by the year 2080.
The most recent flood warnings for the river were issued on December 21 last year, when water levels were the highest they had been since the 2000 flood.
The project would reduce the flood risk by creating a water storage area 50 miles upstream and improving flood embankments in Woodford and Ilford.
The agency does not yet know exactly how much the project will cost and was refused funding by the Greater London Authority but still hopes to start work in October next year.
Cllr Huggett added: “My concern is we have this amazing project but how realistic is it if we do not get the funding.
“I think there’s a grave risk it might not happen. The Environment Agency is struggling with the money but it has to lobby harder.”
The Environment Agency has applied for funding from the Department of Education, due to the risk of schools being flooded, and Highways England but is still waiting to hear back.
An Environment Agency spokesperson said: “The Environment Agency is committed to reducing the impact of flooding to over 600 homes in the Redbridge area as well as improve access and provision of green infrastructure including tree planting to reduce noise and air pollution for local communities and the removal of barriers to fish passage.
“Since 2000, the area has suffered eight times as a result of flooding from the River Roding with more flooding likely in the future due to climate change.
“In July, the Government announced £5.2bn of long-term investment to help protect 336,000 homes and businesses across England from flooding.”