Recent rainfall forces dam closure in Chatham, Ont., creek to divert water around city

Recent heavy rainfall has caused a southwestern Ontario conversation authority to put one of its flood control plans into action.

The Chatham area has seen between 40 to 55 millimetres of precipitation in the past 24 hours or so, according to the Lower Thames Valley Conservation Authority (LTVCA).

Spokesperson Jason Wintermute says a rising McGregor Creek has forced them to close the gates on the dam to divert water around the city — and bypass homes and businesses to the south end of Chatham, in the Indian Creek area.

"The here's too much water coming toward the city down the McGregor Creek watershed," he said.

Wintermute says they closed the dam around 6 p.m. Sunday.

"Levels are still high all over. All over around town."

McGregor Creek is a large watershed that ends up halfway between Chatham and Highway 401. The diversion route was built in the early 1990s to help an area of the municipality that historically experienced flooding, according to Wintermute.

He says, at this point, the creek is still climbing, and it'll probably be some time before it recedes enough to reopen the dam.

"Last time I looked [it was rising] until about an inch an hour," Wintermute told CBC News around 10 a.m. Monday. 

"That's got to stabilize first before it starts dropping. But it probably needs to drop about a metre, actually."

What about the Thames?

As for the Thames River, Wintermute says levels aren't too high and they'll continue to monitor.

"I don't know that we'll get to the point that we have to operate that." 

"It's mostly rainfall," he said. "We've had pretty moderate snow compared to, let's say, the city of London has, and the warm temperatures, that's all really melted away." 

Wintermute says the Thames is expected to peak in the London area today — and that will give them a better indication of what to expect once the water makes its way west over the next few days.

"The early forecasts were that we really weren't going to see water getting into the over banks of the Thames down here. We're not really expecting the river to get out of its banks in any substantial way to effect any houses, it'll just get out into the farmlands and stuff like that."

Levels, conditions elsewhere

The St. Clair Conservation Authority (SCRCA), covering parts of Chatham-Kent and Sarnia-Lambton, says it's seen between 15 and 45 millimetres of rain over the past 48 hours.

Spokesperson Emily De Cloet says the Sydenham River has risen more than one metre during that time and they're receiving reports from municipalities of road closures due to flooding.

"The SCRCA will be upgrading its flood message from a watershed conditions statement — flood outlook to a flood watch," De Cloet said in an emailed statement.

Water levels are continuing to rise across the region, spilling into surrounding floodplain and onto roads. Lambton County road closures due to flooding have been confirmed for:

• Stanley Line from Kimball Road to Waubuno Road.
• Pretty Road. from Stanley Line to McCallum Line.
• Plowing Match Road from Petrolia Line to Rokeby Line.

Further flooding is anticipated as the influx of water continues to move through the watershed to the southern reaches of the Sydenham River.

James Bryant with the Essex Region Conservation Authority (ERCA) says some areas within their oversight have seen up to 50 millimetres of rain over a 36-hour period.

"As a result, major watercourses and tributaries have high water levels, with some areas in bank-full conditions," he said in an online statement. 

"Major watercourses have spill beyond their normal low-flow channels and into the adjacent low-lying floodplain. Water levels are expected to remain elevated throughout the next few days as the watercourses drain toward Lake St. Clair, the Detroit River and Lake Erie."

What's to come?

Bryant said with temperatures expected to remain above freezing for the next few days should help tributaries continue to drain.

"People are encouraged to take extra caution and avoid any areas where flooding may be occurring as well as rivers, streams, and shoreline areas during significant rainfall and wind events."

Barbara Napido with Environment Canada says the late December rainfall is because of a warm air mass making its way north from the U.S.

"The temperatures rise, so, we got the humidity," she said. 

"It's going to fall as a rain instead of snow." 

Napido says to expect a mix of precipitation later in the week as rain shifts to flurries as temperatures fall.

"The water that you can get in the atmosphere, it's not going to freeze."