Flooding narrowly averted in Courtenay

The absence of weekend flooding does not mean the danger did not exist, says City of Courtenay administrator Sandy Gray.

The absence of weekend flooding does not mean the danger did not exist or that the City of Courtenay should not have taken it seriously, says administrator Sandy Gray.

“It was no practice for us,” he said Monday in an interview. It was very close.”

The City issued a joint warning with BC Hydro on Thursday that alerted people to the danger of flooding in low-lying parts of the city near the Courtenay River.

“We got to (river) bank level,” Gray noted. “We were just inches from flooding.”

“It was a very intense storm, but of short duration,” Stephen Watson of BC Hydro said Monday in an interview. “The river (Puntledge) came up quickly … and immediately came down.”

In a statement Sunday, Watson said a high tide occurred Sunday at 7:44 a.m. simultaneous with peak river flows.

Flooding was prevented, he said, by decreased wind, which lessened the storm surge influences at the mouth of the Courtenay River, and BC Hydro’s ability, given the low reservoir level in Comox Lake, to prevent as much water as possible from being released below the Comox Dam.

BC Hydro also held off on restarting the generating station by two hours to 11 a.m. on Sunday given the high river flows, mainly in the Tsolum.

Even so, he said Comox Lake, the reservoir from which Hydro draws water to generate power from its dam high on the Puntledge River, rose 1.6 metres from Saturday night to Monday morning.

Water flowing from the lake into the Puntledge was 1.3 metres from free-spilling over the dam, he said Monday.

The Browns and Tsolum rivers peaked almost in tandem with the high tide Sunday, Watson said in the statement.

The Browns River hit a peak of 78 m3/s at 6:20 a.m., and with the water travel time once it hits the Puntledge River and eventually the Courtenay River, would have arrived close to high tide mark.

The Tsolum River that flows almost directly into the Courtenay River, was flowing at 216 m3/s during the high tide, and peaked at 234 m3/s at 11:30 a.m. That amount of river flow is about 43 m3/s off its historical record peak.

Hydro’s gauge 10 at the Fifth Street Bridge hit 4.05 metres at the high tide mark. Localized flooding can begin only about 15 centimetres above that level.

All river and tributary flows into the Courtenay River totalled around 360 m3/s at high tide, with BC Hydro’s contribution just 20 m3/s. 400 m3/s has been the historical threshold level that caused the floods in 2009 and 2010, though high tides and storm surges create uncertainties.

During the day BC Hydro will hold its water releases to typical seasonal levels (45 cubic metres per second), he said, while warning people to stay away from Comox Valley river systems due to floating debris and continued seasonally high river flows.

Hydro might release extra water this weekend to create room in the lake for future storms as well as giving kayakers a chance to have a thrilling ride down the Puntledge.

Hydro and the City of Courtenay were in close contact during the weekend, Watson said.

“Given our ability to help and the need for co-ordination, BC Hydro participated in Vancouver Island Regional Provincial Emergency Preparedness calls, and communicated with the City of Courtenay throughout Saturday and Sunday, sharing information and situational awareness.”

“Kudos to BC Hydro,” Gray said. “They just shut everything off.

“I can’t say enough about the co-operation wioth those guys. there was nothing coming out of the dam.”

editor@comoxvalleyrecord.com