Devastating flooding that's destroyed and damaged homes along a huge stretch of the Ottawa River is a "natural disaster" and not caused by hydroelectric companies mismanaging the dams, insists the agency that oversees the river.

Some 4,000 people have joined a Facebook group calling for an "independent public inquiry" into possible dam mismanagement during the second major flood on the river in two years.

In the Outaouais community of Mansfield-et-Pontefract, Que., council has passed a motion calling for an inquiry into whether reservoirs and dams along the Ottawa River are being used properly to prevent flooding.

On social media, the flash point focuses on the Ottawa River at the town of Deux Rivières, Ont., which is upstream from the Des Joachims generating dam, 200 kilometres northwest of Ottawa.

Sue Samson's cottage at L'Isle-aux-Allumettes is only accessible by boat because the road has washed away. Two of her sheds have also floated off. (Sue Samson)

Sue Samon's sister-in-law's cottage sits on the same road in L'Isle-aux-Allumettes as her own cottage. It's come off its supports. (Sue Samson )

'They made mistakes'

Photos have been shared hundreds of times showing dry river banks and a seemingly low river level. The images have outraged people whose homes and cottages downstream are submerged — including Sue Samson.

Samson owns a cottage on L'Isle-aux-Allumettes, and added her name to the petition because her dwelling is surrounded by water and only accessible by boat.

Her sister-in-law's cottage has also come loose from its supports, and one end is now tilted over into the cottage next door.

When the Ottawa River Regulation Planning Board (ORRPB) explained why the water level is being kept low upstream from the dam, however, she said she didn't believe it.

"I think it's mismanagement by dam operators and the ORRPB. They made mistakes," Samson said. "They should be able to compensate for all that snow and rain."

Sandbags and a dirt berm try to block the floodwaters from spilling onto a street in Mattawa, Ont., on May 11, 2019. (Michel Aspirot/CBC)

Protecting Mattawa

Manon Lalonde, executive engineer with the Ottawa River Regulation Secretariat, acknowledged the water level is low at Deux Rivières and for many kilometres upstream, but said that's necessary to control flooding elsewhere.

The Des Joachims dam, she said, is the most southern reservoir in the system and has very little capacity to store rising water thundering down from upstream.

Allowing it to fill would cause water to back up in Mattawa, Ont., where the situation is already bad, Lalonde said.

"If we raised the water level in the Des Joachims reservoir, that would increase the flooding upstream in Mattawa, which is already flooded by half a metre," she said.

"There would be such a small benefit for people downstream because it would only reduce the water level by 10 centimetres downstream — and it would only be for three days, because the reservoir would fill up again."

Manon Lalonde, executive engineer with the Ottawa River Regulation Secretariat, says her agency must do a better job of communicating how it manages the river during devastating floods — even if it's difficult to explain. (Jean Delisle/CBC )

An image of the Ottawa River near the Des Joachims dam taken on May 11, 2019. Lalonde says while water levels near the dam are low, the river itself is still flowing very swiftly. (Michel Aspirot/CBC)

'Not a dry river'

Lalonde said photos taken at Deux-Rivières only show the wide flat river banks and that the river, which isn't visible in the photos, is flowing at a very high rate.

"It's a perception problem, and not a technical one," she said. "It's not a dry river there."

Ottawa Riverkeeper executive director Patrick Nadeau said he agrees with that assessment.

"A lot of fingers have been pointed at dam operators, but the water coming down the river is unprecedented," he said. "They are doing what they can."

"There's no easy answer here, It's counter-intuitive," he added. "But [what] dam managers are trying to do is balance things out with low water levels in order to try and protect upstream communities from heavy flooding."

Ottawa Riverkeeper executive director Patrick Nadeau says while it may seem counter-intuitive, low water levels on certain stretches of the river show suggest that the dams and reservoirs are being managed properly. (Laurie Fagan CBC )

Communication could improve

Nadeau's group has been advocating for an Ottawa River watershed council to look at dam operations during flooding, along with climate change and land use planning along the waterway.

The council would serve as a hub for getting important information to the 200 municipalities along the waterway about their stretch of the river during spring flooding, he said.

"Communication is clearly not where it should be," Nadeau said.

Lalonde said the ORPPG is aware they have a public relations problem on their hands.

"We need to communicate in better ways with the public," she said, especially concerning the management of the Des Joachims dam.

"We need to do a lot better with videos and go out to more communities throughout the year, but it's a challenge to make it easily understandable."