Photo of the Puntledge River. (Vista Radio files)
BC Hydro is extending its public safety advisory to stay away from the Puntledge River through next Monday.
It says because the amount of weekend rain was heavier than forecast, flows will be high and dangerous.
Spokesperson Stephen (Steven) Watson says they recognized the evolving situation last Friday, and increased the discharge from the Comox Dam that night to 110 cubic metres per second.
It’s been held there ever since, and Watson says this is not an uncommon flow rate during storm events.
About 85 millimetres of rain has fallen in the upper watershed since yesterday.
This morning, seeing the significant rise in the downstream Browns River and the Tsolum River flows, as well as ocean storm surge from winds, Watson says they reduced the discharge from the dam to 65 cubic metres per second for four hours prior to the 10:25 am high tide.
“Only as of noon, due to ocean storm surge and downstream river flows, have we begun to increase flows from the dam,” Watson said.
“The water release will move to about 150 m3/s by this evening.”
The peak hourly flow rate into the Comox Lake Reservoir today from the rain was between 250 and 300 m3/s. That flow rate would fill an Olympic-sized swimming pool in about nine seconds.
For flood risk considerations, the water survey gauge located at the 5th Street Bridge hit a high of 3.93 metres this morning, Watson noted.
The river flow rate at the time was only about 310 metres per cecond, of which 65 metres per second was from the Comox Dam.
Watson says that is one of the key gauges in the watershed that BC Hydro monitors closely.
“The storm surge from the winds added another 0.8 metres to the tidal height. This is with the high ocean tide of 4.6 metres, which is at the low end of the tidal cycle. The potential for isolated flooding near this location may begin above 4.2 metres,” he added.
“It’s all about timing, as in early November the high tide will be 5.1 metres or 0.5 metres higher, and the king tides later on in December and January will reach 5.4 metres.”
The Comox Lake Reservoir is currently at 134.65 m and rising. The level may peak tonight or early tomorrow around 135 m, below the dam’s overflow spillway level of 135.3 m.
The weather forecast looks wet but getting slowly better tomorrow onward, Watson said.
“The reservoir level will begin to decline tomorrow and through to next Monday,” he added. “As to the ocean tides and the forecast, other than this morning, we will likely just hold the discharge rate from the dam at 150 m3/s or less.”
“With the high water conditions, we will be unable to target our weekly two-day salmon migration flow for Tuesday and Wednesday.”