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All signs are pointing to widespread flooding this spring in traditionally flood-prone areas of Ottawa and the Valley, experts say.
Both the Rideau Valley and the Mississippi Valley conservation authorities issued advisories this week warning that conditions are ripe for flooding – though likely not until next month.
“It is very likely that overbank flooding will occur on most watercourses, affecting access to residences and potentially causing flood damage to buildings and their contents in some flood-prone areas,” the Rideau Valley authority’s advisory said.
Given current conditions, added the Mississippi Valley authority’s general manager, Paul Lehman, “we think it’s prudent for municipalities and residences that are traditionally prone to some flooding to take some precautions at this point.”
And, warned Dave McCartney, Ottawa’s manager of waste water and drainage services, if weather conditions are unfavourable or there’s an ice jam, “we’re going to have water all over the place, and it’s going to be a real mess. We could have flooding just about anywhere.”
If the worst happens, there isn’t much anyone will be able to do, Mr. McCartney said. “Mother Nature takes over.”
The water content of the snow pack in the Rideau and Mississippi watersheds is at or near record levels – a strong indication that spring floods are in the offing.
In the Mississippi watershed, water content in the snow averages 210 millimetres. That’s the highest since measurements began in 1980.
Before this week’s rain, the Rideau Valley authority measured 154 millimetres of water equivalent – second only to 1976, when the watershed had its worst flooding on record.
Patrick Larson is the senior water resources technician with the Rideau Valley authority.
Mr. Larson said flooding is likely along the Rideau River in a zone stretching from Brewer Park in Ottawa South through Sandy Hill as far as Stanley Avenue in New Edinburgh. Britannia, on the Ottawa River, is also a “prime area,” he said.
Richmond, on the Jock River, and North Gower, along Stevens Creek, are vulnerable, he said, while residents along the Rideau River near Kemptville “will definitely” experience some degree of flooding.
Perth, which is bisected by the Tay River, is also at risk. There’s actually more snow in the Tay basin than there is in the Jock River, Mr. Larson said.
Mr. Lehman said Constance Bay and areas along the Carp River, including Kinburn and Carp, could well see flooding. Other at-risk areas include Pakenham, Dalhousie Lake and Mississippi Lake, where year-round residents are slowly supplanting seasonal cottagers.
Mr. McCartney expects the spring melt will test the drains in the Glen Cairn section of Kanata, which was flooded by summer rains a few years ago.
“We’ve done a lot of work out there improving the system,” he said.
“Hopefully it will perform as advertised.”
The dangers posed by the spring melt prompted the Children’s Hospital of Eastern Ontario to issue a warning to parents on Thursday to keep their children away from ditches, creeks, ponds, rivers and lakes.
Mona Jabbour, medical director of CHEO’s emergency department, said parents “need to be aware that these risks are real,” adding that a child can drown in as little as five centimetres of water.
The Ottawa OPP also reminded motorists to avoid driving into water pooled on the road that might conceal holes or debris.
With below-seasonal temperatures forecast for the rest of March, flooding is unlikely to occur before April, Mr. Larson said. But the longer cool weather persists, the greater the likelihood of rapid warming that would quickly melt the snow pack.
Both conservation authorities advise people in flood-prone areas to make sure their sump pumps are in good order and remove or secure anything on their property that could be affected by flooding.
Mr. McCartney said the most important thing people can do is make sure catch basins on their street are clear. He also advised homeowners to dig snow away from their foundations to reduce the risk of water seeping into basements.
Sandbagging is the ultimate defensive measure. While it’s too early to start deploying bags, Mr. Larson said people concerned about flooding should be checking where they can get them.
Areas at greatest risk of flooding this spring: