The president of the Alouette River Management Society said the river was another eight hours of intense rainfall away from creating a disastrous flood.
Record rainfall saw 178 mm measured at the Pitt Meadows weather station from Nov. 13-15. It filled the Alouette Lake reservoir, and water was flowing over top the BC Hydro dam there. There was nowhere for more water to go, except down the swelling river. Hydro issued a flood alert notice on Monday, and told Maple Ridge Search and Rescue to be prepared to hand out evacuation notices.
At 1 p.m. on Monday, the water level had crested the dam.
Then, fortunately, the deluge of rain stopped at 2 p.m.. If it had continued until about 10 p.m., the situation would have been dire, said Ken Stewart.
“If we had another eight hours of rain, Maple Ridge and Pitt Meadows would probably be looking like Sumas right now,” said Stewart, referring to the farmland in east Abbotsford that is flooded and had to be evacuated.
He explained the Alouette Lake drains a large watershed, and if all that water could not be contained behind the dam, it would all come down the narrow riverway, slowed only by bridges at 232nd Street, 224th Street and 216th Street, where large lakes would form.
“We would have had real problems,” he said. “We just got lucky.”
BC Hydro watched rising water levels, and opened the flood gates to allow more water out of Alouette Lake. Stewart is suggesting that should likely have happened earlier, to keep the reservoir from filling up. ARMS will be making that recommendation to Hydro.
“It should also be a wake-up call to cities not to build in flood plains.”
Coun. Gordy Robson agreed with Stewart’s assessment. Robson was mayor from 2005-2008, and recalled a similar event in 2007. He was summoned to city hall to make decisions about emergency action, if the river continued to rise.
“We were just waiting to make announcements,” he said.
Then, the rain stopped, and the crisis was averted.
He was reminded of that event, and knows of the worst Alouette River flood in 1955, when homes were damaged beyond repair in Maple Ridge, cattle drowned in Pitt Meadows, fields flooded and roads washed out.
Robson was watching the BC Hydro website showing the water level rising consistently as the rain poured on Sunday night and Monday. Just as it rose above the dam, the rain stopped.
“We just dodged a bullet again,” he said.
Stewart said the old ways of trying to manage the flood plain are no longer relevant with the changing weather. He said the city and Hydro should discuss operations during future rainfall events brought by atmospheric rivers.
READ ALSO: ‘Atmospheric river’ drenches Lower Mainland, leading to flash flooding
“We know this was an extreme event, given how far this went, but this is what we’re predicting now, with climate change,” he said. “This is going to happen more often.”
READ ALSO: Levee to be built in Abbotsford to hold back surging floodwaters from Highway 1
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