Owaka resident Jenny Kinley, whose son and family live opposite the new site, said people remained "angry" about the "invisible" council consultation process.
She said many now feared the consequences of freedom camping seeming to be "encouraged" in the town.
"We're terribly afraid that when it gets cranking it will be chaos. Already it was very noisy on Saturday night when I visited my son, and even with relatively small numbers of visitors there are signs traffic, litter and general behaviour could be a problem."
Both Hewson and Kinley emphasised the need for "effective" monitoring of the site by the council's responsible camping ranger, Scott Martin.
Hewson also wanted to see signage erected deterring campers from parking at undesignated sites in the town and district.
"I haven't seen Scott yet, but there needs to be someone here at peak times checking on self-containment, behaviour and noise.
"Otherwise it just won't work."
While acknowledging the project had "polarised" residents, Clutha Mayor Bryan Cadogan said the council was happy to see the trial begin.
"This will fulfil the need for the vast majority of people in the Catlins. We look forward to a successful trial."
The project had come in under its budget of $25,000, and would be reviewed at the end of the season.