The developer of the multimillion-dollar project, Port Otago, is keeping a watching brief on the situation.
Three rock groynes at Te Rauone Beach appear to have successfully retained sand and have helped to transform the area into a popular destination, but erosion has been happening just south of the southernmost groyne.
It is hoped beach nourishment will remedy the situation, but Graeme McLean is one Harington Point Rd resident worried this might not be enough.
He has gone as far as suggesting a fourth groyne could be required.
"We want a bit of action," Mr McLean said.
Nearby property owner Trisha Geraets said erosion in the area was a worry.
About $17,000 of work was done on her property last year, using rocks as a defence against erosion.
Harington Point Rd resident Amber Paterson said ongoing deterioration of the environment was troubling to witness.
"To see it washed away on a daily basis is really quite heart-wrenching," Mrs Paterson said.
Another resident, Des Grey, said waves were coming in at a different angle since the groynes were built, "causing accelerated erosion on [their] bank".
Port Otago has led the $3 million groynes project.
Port chief executive Kevin Winders said the beach was a fantastic asset, but there was more work to do.
"Clearly, we’re looking for a great result for everyone."
It was explained in the application document erosion south of the groynes had been anticipated, but it arose "earlier than expected" as it was "exacerbated by the inability to get the main sand renourishment work under way immediately following groyne construction".
Lack of availability of a pump for dredging had caused a seven-month delay.
Some nourishment was attempted south of the groynes late last year, but residents said sand quickly dispersed.
Mr Winders said engineering consultancy firm Beca would evaluate the environment and he expected it would take some time for the beach to settle.
In a letter to the port, Mr McLean said residents wished to compliment the port on the work to date.
However, he also raised a series of issues, ranging from responsibility for maintenance of rock revetments to doubt about sand staying in place.
