Children face having to wade through raw sewage on their way to school along a busy Brighton road.
Foul water has been filmed pouring out through manhole covers in Winfield Avenue, by Patcham High School, this week.
The road is also used by some children going to Patcham Infant School and Patcham Junior School.
Parents and residents are urging councillors to take up their complaints with Southern Water and Brighton and Hove City Council.
The council has been in talks with Royal Mail about the possible siting of a new distribution centre at Patcham Court Farm.
Neighbours fear that floods would be more frequent and worse if the planned depot goes ahead and that foul water would pollute the local aquifer which supplies drinking water to more than 100,000 people.
One resident said: “This week, residents in Patcham have been reporting lakes of raw sewage engulfing Winfield Avenue opposite Patcham High School in north Brighton.
“Residents say they have reported this problem to Southern Water and the council for many years but it is still a recurring issue.”
Councillor Anne Meadows has called for action and said that she would raise the flooding problem at the council’s City, Environment, South Downs and the Sea Committee next Tuesday (14 November).
Councillor Meadows said: “It is totally shocking that in 2023 the residents of Patcham are regularly exposed to flooding and school children have to battle with raw sewage on their way to class.
“It is ridiculous that Royal Mail has been able to put in an application to build an industrial site that will directly increase the flooding risks in the area.
“I am concerned that the flooding issue here has never been taken seriously enough and that is why I am taking it to committee.”
The Patcham Against Royal Mail campaign said that the Royal Mail’s application to build on Patcham Court Farm would exacerbate flooding incidents that have already plagued the area.
Residents said that they had seen raw sewage and dislodged manhole covers this week after heavy downpours of rain.
They are worried about the considerable health risks associated with raw sewage such as e.coli, as well as the expensive cost of damage caused by floods.
The council’s flood mitigation team and Southern Water have recommended that the Royal Mail’s plans are refused but the controversial proposals are currently still in contention.
Patcham Against Royal Mail co-lead Mike Howard said: “We are concerned that Royal Mail has been able to submit an application for Patcham Court Farm based on inaccurate information and desk research.
“They are trying to mislead the public about a number of important issues and fail to acknowledge that their proposals will impact the flood risk in Patcham and may overspill on the critical A23 and A27 road network near by.
“Royal Mail must drop their plans for Patcham and pursue their alternative and safer plan around Shoreham.”
Campaigners said that the Royal Mail’s plans to pave over the ground at Patcham Court Farm would effectively block the aquifer and cut off the water filtration process on the site near Southern Water’s Waterhall pumping station.
As a result, rainfall in the area would be diverted to sewers and wasted. Residents are concerned that overloading the sewers may also further increase the frequency and severity of flooding.
Campaigners said that Patcham Court Farm played an important role in the area’s flood defences. The chalky terrain where the farm is situated has a capacity to absorb water and replenish the underlying aquifer.
This land, comprising of Seaford chalk, acts as a natural filter for groundwater, contributing to the tap water supply for approximately 116,000 people living in Brighton and Hove.