A developer's consultant made a significant error while predicting the potential for flooding at a proposed development along the Carp River in Kanata West, and that discovery has prompted the City of Ottawa to put the project on hold.

"No development will occur in this flood plain until the city is satisfied that this matter has been properly addressed," Rob Mackay, acting director of the city's economic and environmental sustainability branch, said Monday.

City engineer and stormwater expert Ted Cooper, who has been fighting the development, estimated the error could change flood level predictions by as much as a metre for the proposed 700-hectare development, along Highway 417, near Scotiabank Place.

Mackay said the error was enough to "warrant us to be concerned" and could require plans for the project to be revised.

The mistake in question was a coding error in a computer model, and as a result, the model failed to account for runoff from the development itself, said Mackay.

The model was part of an environmental assessment prepared by Totten Sims Hubicki Associates, consultants hired by landowners who want to narrow the flood plain to build on 28 hectares of land reclaimed in the process. Its predictions would be used to decide how to do that, and design the placement and elevation of roads and infrastructure.

Mackay said the city is hiring an independent third party to examine the project.

In addition, Alain Lalonde, the city's auditor general, has told staff he is investigating the project for his upcoming annual report.

The project had already been approved by two levels of government.

However, it has been slowed down by provincial challenges against it.

Error noticed

Cooper, who was suspended and reassigned after he raised concerns about developing the Carp River flood plain years ago, is fighting plans for the development before the Ontario Municipal Board, and is also appealing to the Ministry of the Environment.

He said without his complaints and others, there might already be shovels in the ground.

"Basically in this case, when you've had all the provincial agencies and municipal departments sign off on it, the only line of defence have been the appeals that I've initiated and others have initiated on this project," he said.

Cooper received a copy of the computer model last week after requesting it in November to prepare for an upcoming municipal board hearing. He said he noticed the error within a day.

Kanata South Coun. Peggy Feltmate, who heard about the error on Jan. 24, said she wonders how the city, two provincial ministries and the local conservation authority, which all approved the plan to narrow the flood plain, could have missed it for so long.

She added it may be time to reconsider the practice of allowing developers to hire their own environmental consultants.

"Often at this point there's a distrust in the public because they feel that the consultants are paid for by the developers, by the proponents who have the money and he who pays the piper calls the tune," she said.