Thousands of people visited the blue flag beach over the weekend to enjoy the sunshine.
Independent Councillor Niamh Kennedy said there were only four bins on the 3km stretch of coastline and this created "mayhem".
The beach is a popular destination for visitors from Northern Ireland.
Local people collected the rubbish from the beach on Sunday and Monday after visitors had left.
The refuse left behind included deck chairs, barbecues, food waste, glass bottles and nappies.
Paul Diver, from the Sandhouse Hotel in Rossnowlagh, said the majority of people that visit the area "behave impeccably".
"A bigger issue is traffic and the lack of toilet facilities, there were three portaloos and our hotel became the public toilets for the weekend," he added.
Cllr Kennedy agreed that a lack of toilets and traffic management at the site were causing problems.
"Once the sun comes out it's bedlam," she said.
"Cars are allowed on the beach-but there is a safety issue."
"The cars were blocking the entrance, then the tide comes in and there's a big scramble, every year there are cars destroyed."
She added: "If there was something serious you would never get an ambulance down."
Last year cars got caught out by the tide at Rossnowlagh beach.
Cllr Kennedy said council resources were insufficient to properly look after the beach.
"The resources are not there," she said. "It will be a community effort to try and address the issues, but council will have to help and back them up."
She warned: "The beach could lose its blue flag status if this keeps up."
The council said the amount of litter left on the beach was "extremely disappointing".
"Donegal County Councils Litter Management team had a presence on Rossnowlagh beach over the weekend and they carried out clean ups on Tuesday and Wednesday," it said in a statement.
The council said that its traffic management plan had been reviewed and they are working with the local community."
A Donegal councillor has complained after visitors to Rossnowlagh beach last weekend left "huge amounts" of rubbish behind.