Flood watch in Hamilton issued with rain expected in 2 days

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Published January 10, 2023 at 6:16 pm

Feb. 9 Weather: It will be the hottest day ever recorded in southern Ontario

The prospect of Hamilton receiving its third significant rainstorm in under two weeks has triggered a flood watch.

Hamilton Conservation Authority (HCA) notes that some forecasts say somewhere in the range of 20 to 26 millimetres of rain could fall on Thursday (Jan. 12), when showers are in the forecast. As such, rising water levels could pose a safety risk, especially to children and family pets.

“Water levels and flows in area watercourses are expected to increase significantly, as a result of the forecasted rain on January 12,” HCA says. “Localized watercourse flooding of low-lying areas that typically flood during higher water levels is also anticipated.

“In addition, there is some potential for significant watercourse flooding, as increased amounts of rain runoff may occur given the frozen soil conditions within the watershed.

“A close watch on local conditions is recommended. Also, HCA wishes to remind residents to exercise caution near all water bodies and structures such as bridges, culverts and dams during this time. Elevated water levels, faster moving water, rapidly changing levels and flows, and slippery banks may pose a significant hazard. Adults are advised to keep children and pets away from water bodies at this time.”

The forecast for Thursday in Hamilton from Environment and Climate Change Canada (ECCC) says, “Cloudy with 60 per cent chance of showers. High plus 5.”

The conservation authority emphasized there is “considerable uncertainty” about how much storm runoff could occur due to the anticipated rains.

Per ECCC, Hamilton has had two significant rain days within the past two weeks. A week ago Wednesday, on Jan. 4, 16.6 mm of rain fell on the city, accompanied by maximum wind gusts of up to 60 km/h. Four days earlier, on New Year’s Eve (Dec. 31), there was 16.3 mm of total rainfall.

That means the city’s water levels and area watercourses are, in HCA phrasing, “elevated above baseflows… there are no flooding concerns or public safety concerns at current conditions.”

Already this month, 22.4 mm of rain has fallen in Hamilton, and the daytime high temperature has been above freezing (OC) every day. But the city is not too far removed from a very rain-soaked January. In the first month of 2020, the city received 80.8 mm of rain. More than half of that, 41.2 mm, fell on Jan. 11 of that year.

The wet weather comes amid Hamilton Water working to identify and repair incorrect “cross connections” between sewage pipes and storm sewers. Two instances of improperly connected pipes, which caused untreated wastewater to flow directly into Hamilton Harbour for over a quarter-century, have been found by the city in the last seven weeks.

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