North Shuswap Kicker May 2022

Spring Flood Risk (Freshet)

By Jo Anne Malpass Flooding is a provincial risk every spring due to a combination of snowmelt and/or rainfall (also known as freshet). Every region is at risk for flooding, even if the snowpack is below normal, says the BC River Forecast Centre.

Spring weather conditions play a critical role in the rate at which the snow melts. For example, a gradual warming under dry conditions is ideal to lessen the flood risk. A lengthy cold period with high amounts of precipitation followed by a sudden extreme heat wave could lead to catastrophic conditions, especially if additional rain follows.

Typically, regions with above normal snowpack have a higher risk for flooding. As of April 15, the provincial average increased to 107% of normal. Most regions have remained level or measured modest increases of +1 to +3 percentage points. The April 18 storm provided additional snowpack with many regions bumping up further.

By April 15, on average, approximately 100% of the total seasonal snowpack accumulates. “Based on current weather patterns, this year is likely to continue adding mountain snowpack beyond April 15 as opposed to 2021 which began melting in mid-April from a heat wave event.”

The April 1 Snow Survey and Water Supply Bulletin showed the North Thompson measured 119% of normal, which is the highest index since 1999.

“Additionally, Shuswap Lake levels have been above average this year and were at historic highs over the winter due to the extreme rainfall from the atmospheric rivers in November 2021.”

The most likely cause for major flooding would be a period of persistent cool temperatures and wet weather into the late spring, followed by a sudden heat wave lasting at least five days. There is evidence that the 1948 and 1894 floods on the Fraser River were caused by this scenario. The snow conditions for April 1 in 1948 were considered slightly above average (based on current snow stations that had measurements in 1948), showing the importance of spring weather to flooding. A secondary risky scenario is a widespread heavy rainfall event that occurs during the high flows from snowmelt. Spring weather is impossible to predict with accuracy in advance, says the River Forecast Centre, and so communities and residents vulnerable to flooding should prepare accordingly; information for Be Prepared for Floods is available from

Here are some tips from the BC Public Safety Ministry to help prepare for flooding:

Clear debris from gutters and downspouts, and have a household plan ready.

Elevate and anchor utilities, such as heating systems, electrical panels and sockets.

Keep clear of eroded banks as they may result in unstable ground. Keep children and pets away from stream banks.

With higher water levels, boaters and water users can expect increased debris. Boaters should be aware of the impact that their wake can have on shorelines and reduce speed accordingly. Wave action can cause erosion or flooding.

Never drive or walk through flooded streets. Water can be deeper than it appears, and levels can rise very quickly.

Stay alert for changing conditions, particularly if you live in low-lying areas or near waterways.

The Flood Preparedness Guide is available online: www.preparedbc.ca/floods