Ministry of FLNRO

Flood Warnings and Advisories

High Streamflow Advisory - Somass River (MAINTAINED), South Vancouver Island (MAINTAINED)
ENDED - High Streamflow Advisory – East Vancouver Island
ISSUED: November 23, 2017 11:30 AM

The River Forecast Centre is maintaining a High Streamflow Advisory for:

  • Somass River including Sproat River, Stamp River and tributaries
  • Southern Vancouver Island including the Nanaimo River, Chemainus River, Cowichan River, Koksilah River and surrounding areas

The River Forecast Centre is ending a High Streamflow Advisories for:

  • Eastern Vancouver Island including the Englishman River, Tsolum River, Oyster River and tributaries around Campbell River, Comox, Parksville and surrounding areas

A series of storms has passed over Vancouver Island over the past two days. Rainfall totals over the past 2 days have been in the 100-250 mm range in the western portions of the Vancouver Island, 50-120 mm in the Sproat/Somass watershed, and 30-80 mm on the eastern side of the Island. Warm temperatures have also led to snow melt, particularly at mid-elevation, with 25-40mm of melt observed at automated snow weather stations across Vancouver Island (Jump Creek, Heather Mountain, Mount Arrowsmith). Rainfall rates have now eased.


River levels have peaked from this rainfall. Levels remain elevated in the Sproat River, and are slowly receding downstream on the Somass River. Flows are expected to continue to recede on Thursday and into Friday, however additional rainfall later in the week (Friday to Sunday) may lead to additional rises along the Sproat and Somass Rivers.


On Southern Vancouver Island, river levels on the Cowichan River and Nanaimo River, are approaching or at peak levels from this rainfall. Flows are expected to remain high through Thursday, and recede into Friday.


The River Forecast Centre will continue to monitor conditions and update this advisory 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.