Mrs Harris said while children love the playground, an absence of boundaries meant a stressful time for parents keeping an eye out on their children.
"I want to emphasise that I don't want a battle. I want to inspire the council to be proactive and creative in their thinking.
"Imagine a space where families can relax and enjoy time with their children without worrying about the danger of the water and carpark. We can look at this positively and use our creative thinking.
"Whangarei was one of the first cities to sign up to the Child Friendly Cities Initiative in 2014 but I feel the council is not putting children first in their decision making," she said.
Mrs Harris moved to Ruawai from Whangarei two years ago but has been taking her children to the playground for nine years.
Although Lower Dent St was not as busy as state highways, she said the road was still very busy, with a bus stop and a major roundabout in the vicinity.
Her petition was signed by 1016 people by 3pm yesterday. Whangarei mother Jade Waiti brought her daughter and a niece to the playground yesterday and supported Mrs Harris' call for the site to be fenced.
"A fence would be ideal because I worry about children standing at the water's edge and running on to the road. You have to always watch them.
"Fencing would make it easier for parents to relax and enjoy the atmosphere," she said.
Another parent, Cicilia Muzembe, also favoured fencing and said it became especially difficult to supervise children during the school holidays.
"The other day I came with a friend whose child ran to the river's edge so fencing will prevent that sort of thing happening," she said.
But another mum Helen Firth felt the beauty of the site would be spoilt if the playground was fenced.
"I think the council is doing an amazing job. Kids have so many things to do here. There's a good flow of amenities where people can come to the playground, hop on to a cafe and go around the loop," she said.
In his response to Mrs Harris, council's parks technical officer Spencer Jellyman said the council received a similar petition in early 2015 for the playgrounds at the Town Basin and at Mander Park to be fenced.
The petition, he said, did not succeed for two reasons.
First, the council felt parents needed to supervise their children at not only playgrounds but also in all public areas.
If they had safety concerns at a site, Mr Jellyman said parents should take their children elsewhere.
The second reason was the council did not want to spoil the attractiveness of the playgrounds by fencing them.
The petition would be eventually presented to council. Council staff would write a report for councillors to consider whether the playground should be fenced.
Those wishing to sign the petition can do so on www.change.org.