Since last week, BC Hydro has been tracking the two sub-tropical storms forecasted to hit the region this week. Unfortunatel,y the storms are now much stronger and may hit the Comox watershed hard. BC Hydro’s weather forecasting and hydrology modelling, as of today, has seen a large increase in rainfall and forecasted inflows.
The Monday-Tuesday storm is the strongest. Precipitation will peak tonight at a rate of about 10 mm per hour.
With the high ocean tides taking place in the morning each day this week, there is a risk of flooding in isolated areas of Courtenay on Tuesday and potentially each morning thereafter through Thursday. BC Hydro is concerned about these storms and the potential for flooding.
BC Hydro is forecasting daily water inflow averages into the reservoir to be 350 m3/s and 320 m3/s on Tuesday and Wednesday. That means hourly peaks may hit 600-700 m3/s. It also means the uncontrolled Tsolum and Browns river flows will be high. Flooding along the river can begin at around 400 m3/s but is dependent on tide and storm surge from wind. There are winds from these storms that will cause some surge up the estuary.
Since the weekend, BC Hydro is spilling water at maximum rates and that continues through today to lower the reservoir level. The reservoir has come down about half a metre the past two days. It is currently at 133.3 metres, and provides BC Hydro with about 2 metres of storage room to try to take in these forecasted water inflows. However, that storage may be taken up fast in the next few days, and with it, BC Hydro’s flexibility to back off during high ocean tides
BC Hydro will operate the Comox dam by releasing high flows at low tide and low flows at high tide. The flow discharge from the dam may be from 30 m3/s at high tide to 200 m3/s or more at low tide. The public is advised to stay away from the Puntledge River through the week.