Communities across much of Eastern Canada are bracing for more flooding today, with rain in the forecast from central Ontario to northern New Brunswick.

Officials in Quebec are keeping a close eye on a hydroelectric dam west that's at risk of failing, while Ottawa's mayor has declared an emergency and part of the Trans-Canada Highway has been closed in New Brunswick.

The Chute-Bell dam west of Montreal has reached "millennial" water levels, meaning a flood that happens once every 1,000 years, but Hydro-Quebec says it's confident the structure is solid.

Simon Racicot, the utility's director of production and maintenance, told reporters yesterday that "we are entering into an unknown zone right now — completely unknown."

Meantime, Ottawa has joined several smaller Ontario communities in declaring a state of emergency, with Mayor Jim Watson requesting help from the Canadian Forces.

Farther east, New Brunswick's Department of Transportation said the Trans-Canada Highway was fully closed from Oromocto to River Glade, and could remain closed for several days.

And there's not much relief in sight, with Environment Canada predicting rain for a large swath of Eastern Canada, from Georgian Bay to the Gaspe Peninsula.