Residents, cottage and business owners on some of the biggest lakes in Muskoka are launching a $900-million class-action suit against the Ontario government because of flooding caused by high water levels.

People living on Lakes Muskoka, Lake Joseph and Lake Rosseau say they suffered extensive damage during this year's spring thaw because of high water and drifting ice that wreaked havoc on docks, boat houses and their properties.

The Ministry of Natural Resources is responsible for controlling water levels in the lakes, and the residents blame poor management and negligence for allowing the levels to become dangerous.

The ministry issued a statement Thursday saying it was "sympathetic" to those who had property damage, but adding that severe weather conditions are out of its control and that the spring melt was earlier and faster than normal this year.

"Over 170 mm of precipitation fell over a very short period of time, combining with high winds and ice flows to cause severe spring flooding," it said. "We have lowered water levels in ministry dams when appropriate. Lowering water levels may provide limited relief from flooding, (ministry) dams were not designed to be flood control structures and don't have the capacity to store or hold back flood waters."

Lawyer Troy Lehman said the extent of the damage is "enormous" but the actual cost of repairs is still unknown, and most residents have not been successful in making insurance claims.

"We picked that number because we don't know the actual amount," he said. "Conservative estimates would say property damage could be in the hundreds of millions of dollars, and that's why that large number was picked, but we will gather that information as people come forward."

Peter Burgess, the representative plaintiff in the proposed class-action suit, which has not been certified by the courts, said it's frustrating to suffer widespread property damage and not be able to afford to fix it.

"It's a terrible feeling to have something crushed by the elements," he said.

The Burgess family waterfront property on Lake Rosseau was flooded twice in the past few years, and its two-storey boathouse collapsed this spring and could cost up to $700,000 to rebuild.

Insurance companies offer 'scraps'

"Insurance companies don't insure wharfs or docks due to flooding or ice damage, but they do insure due to wind damage, so I had to build the argument that it was due to all three elements," said Burgess. "So I still have no money from (the insurance company). They're throwing some scraps on the table."

Cassandra Ford, who operates a marina and restaurant in Bala, said she is looking at up to $400,000 to rebuild a damaged boathouse.

"Nobody seems to care," she said. "They don't care."

Ford wants the ministry to explain why there was no flooding for 60 years and then three major floods since 2010.

"Prior to the 2006 Muskoka Watershed Management Plan we had high water but we didn't have constant flooding," she said.

In addition to monetary damages, the suit also aims to secure a judge's order that would force the ministry to address the issue and maintain safe water levels.