An artist's rendering of what the Lansdowne redevelopment will look like once shops, offices and condos are built on the site. (Ottawa Sports and Entertainment Group)

Parks Canada is warning the Rideau Canal could lose its World Heritage Site status if it is altered to fit proposed redesign plans for Lansdowne Park.

The warning comes from Don Marrin, the Parks Canada official in charge of the canal.

Marrin said Parks Canada can't support any change to the "shape or alignment" of the canal, which would disqualify at least one of the design proposals unveiled last week.

"The form of the channels was part of the designation of the outstanding universal value in the first place, upon which UNESCO designated a world heritage site," Marrin said.

"So on that basis, we don't want to compromise the integrity of that."

Marrin said a substantial change in the canal could prompt the United Nations Educational, Scientific and Cultural Organization to rescind the site's heritage designation.

"There has been precedents where UNESCO has taken away designation of a world heritage status for areas where the reasons for the designation had been compromised," he said. "That is a risk."

Marrin said Parks Canada has no objection to building new bridges or docks on the canal.

Parks Canada will have a say in the selection of the winning design, along with city council and the National Capital Commission.

The news comes just one day after it was announced the Ontario Heritage Trust was concerned about how the development would impact the Horticulture Building on the property and said it was considering seeking heritage protection for the structure.

Three of the five design concepts unveiled last week would move the building to make way for a commercial complex.

No big changes to Lansdowne Community Park

Meanwhile, the head of Ottawa's planning committee is repeating his promise to preserve Lansdowne Community Park.

The 2.5-hectare green space, also known as Sylvia Holden Park, sits next to Lansdowne Park. It contains two baseball diamonds, a wading pool, a play structure and other amenities.

The park was included in the larger Lansdowne redevelopment.

Three of the five firms that submitted proposals last week suggested significant changes to the park.

Coun. Peter Hume, who sits on the review panel judging the designs, said on Wednesday the panel would ensure the park's amenities are kept.

He also said the park will remain in city hands.

Caroline Vanneste, president of the Glebe Community Association, called that a victory.

"It says that you can fight city hall and you can get a group of people together to fight the good fight and convince people that it is reasonable to ask our city staff to talk to us when they're going to make a change to a park in our community," she said.

Sports stadium plans to be unveiled Thursday

The five design proposals are part of a competition focusing on the section of the park bordering the Rideau Canal, toward the southeast. The competition area does not include the northwest section of the park along Bank Street.

City council voted last November to start negotiating a private-public partnership with the Ottawa Sports and Entertainment Group to redevelop Lansdowne Park.

The controversial development plan includes construction of a cluster of shops, cinemas, condominiums and townhouses, and the revamping of the existing stadium.

On Thursday, the city and business group behind the plan to redevelop Lansdowne Park will unveil the proposed design for a new sport stadium and commercial complex.