Snowmelt And Rain To Cause Risk Of Minor Flooding And Ice Jams In Ausable Bayfield Watershed

by Bob Montgomery

Snowmelt and rain are expected to cause the risk of minor flooding and ice jams in the Ausable Bayfield Watershed.

Residents are reminded to stay away from waterways. A low-pressure system, approaching the Great Lakes region, will bring rain into the Ausable Bayfield watershed beginning Tuesday, March 4th. Expected rainfall amounts of 15 to 25 millimetres are forecast to fall Tuesday through Wednesday. Temperatures will remain positive during the rain event, reaching up to 9 degrees Celsius on Wednesday.

The forecast rain and temperatures remaining above freezing over the next two days will melt most of the snowpack. Snow survey data from February 28th shows the water equivalent in the current snowpack ranges between 46-82 mm. This puts most locations above the typical snow water equivalent of 50 mm for this time of year. With a combination of rainfall and snowmelt on saturated soils, a relatively quick runoff is expected.

With water levels in streams already slightly elevated due to last week’s snow melt, the forecast rain is expected to cause a further rise in levels. This could create minor flooding in low-lying areas and close some secondary roads with traditional flooding problems.

This cold winter has led to the formation of thick ice on local streams and rivers, which is now beginning to thaw and break apart. While staff continue to monitor ice conditions, the unpredictable nature of ice jams makes it difficult to predict where and when they will form. Historically, ice jam flooding potential is highest in the lower Ausable River between Ailsa Craig and Port Franks. Minor ice jams have also been observed in the Bayfield River. However, ice jams can occur anywhere when ice is present and lead to unpredictable flooding. In addition to flooding impacts, structures located in, or adjacent to, the water are vulnerable to damage from moving ice. 

Municipal staff should monitor local drainage problem areas where snow conditions may have covered catch basins. Residents are reminded that any ice on local water bodies should be considered unsafe. In addition, use caution near all watercourses as waters may be fast-moving and higher than normal. Slippery and unstable stream banks and extremely cold water temperatures will create additional hazards.

This message will remain in effect until 9:00 a.m. on Monday, March 10th, unless otherwise updated. 

Details also available at www.abca.ca.