Flood Warnings and Advisories
Category: Latest News
Published: Saturday, 23 April 2016 02:47
Written by Nooaitch Communications
UPDATE - High Streamflow Advisory: South Interior
ISSUED: April 22 2016 12:00 PM
The BC River Forecast Centre is maintaining a High Streamflow Advisory for the South Interior including:
- Okanagan – small tributary river systems in the Vernon, Kelowna and Penticton and surrounding areas, including Mission Creek
- Similkameen River and tributaries
- Boundary Region including the Kettle, West Kettle Rivers and Granby Rivers (ADDED)
- South Thompson including the Salmon River and other small tributary systems
- Thompson region including the Nicola River upstream of Nicola Lake and small tributary rivers in the Merritt and surrounding areas
An unseasonably strong high pressure ridge has brought record hot temperatures across much of British Columbia this week. Daily high temperatures have been in the 20 to 30°C range throughout the week. These temperatures are 10 degrees or more above normal for this time of year. Hot temperatures have led to rapid melt of high elevation snow packs. Snowmelt rates have been increasing throughout the week, with daily melt rates in the 15 mm to 40 mm range.
Streams have been responding to this rapid snowmelt, with many smaller streams in the South Interior seeing a 150-300% increase in flow over the past 5 days. Flows in many smaller rivers are near or above record levels for this time of year, with many streams at 2-year to 5-year return period flows. As of 8:30 AM Friday morning a summary of streamflow conditions at Water Survey of Canada hydrometric gauges include:
- Mission Creek near East Kelowna (08NM116) is flowing at 56 m3/s (approximately 2-year flow)
- Coldstream Creek above Municipal Intake (08NM142 ) is flowing at 1.4 m3/s (between a 2-year and 5-year flow)
- Whiteman Creek above Bouleau Creek (08NM174) is flowing at 15.5 m3/s (10-year flow)
- Similkameen River near Hedley (08NL038) is flowing at 423 m3/s (2-year flow)
- West Kettle River at Westbridge (08NN003) is flowing at 113 m3/s (2-year flow)
- Granby River near Grand Forks (08NN002) is flowing at 247 m3/s (2-year flow)
- Salmon River near Falkland (08LE020) is flowing at 31.5 m3/s (between 5-year and 10-year flow) and near Salmon Arm (08LE021) is flowing at 41.5 m3/s (approaching 5-year flow)
- Nicola River above Nicola Lake (08LG049) is flowing at 54.8 m3/s (approaching a 10-year flow)
While temperatures are easing slightly compared with earlier in the week, they are forecast to remain seasonally high (up to 20˚C) on Friday and into Saturday, before cooling occurs into Sunday.
Snowmelt rates are expected to remain elevated on Friday and Saturday, with additional rises in river levels expected. With cooling weather through the weekend Sunday, river levels are expected to recede into Sunday.
Current weather forecasts for next week indicate either additional warming or unsettled weather. River levels are expected to remain stable Sunday through to the early part of next week.
The public is cautioned to stay clear of rivers during high streamflow events due to quickly flowing water and potentially unstable riverbanks.
The River Forecast Centre will continue to monitor conditions and will provide updates as conditions warrant.
A High Streamflow Advisory means that river levels are rising or expected to rise rapidly, but that no major flooding is expected. Minor flooding in low-lying areas is possible.
A Flood Watch means that river levels are rising and will approach or may exceed bankfull. Flooding of areas adjacent to affected rivers may occur.
A Flood Warning means that river levels have exceeded bankfull or will exceed bankfull imminently, and that flooding of areas adjacent to the rivers affected will result.