Flood Watch Issued for Maitland and Nine Mile River Watersheds
Unseasonably warm temperatures, approaching double digits, are expected today (Monday, February 19, 2018) and continuing overnight into Tuesday. In addition to the warm weather, forecasts are calling for 60-80 millimetres (mm) of rain over today and Tuesday before temperatures drop below freezing on Wednesday.
Snowpack water equivalents were measured this past week, and across the watersheds showed values of between 40 – 70 mm of water content on average. After last week’s warmup, the snowpack has ripened to the point where it has no capacity to absorb rainfall before running off. The warm temperatures and rain are expected to melt the snowpack, resulting in rapid runoff. The rate of runoff and impacts on stream flows will be dependent on the actual amount of rain that the watersheds receive. Watercourses will begin to rise through the day today. Levels will continue to rise on Tuesday, with flows not peaking until Wednesday.
Depending on the rainfall, this event has the potential to reach levels experienced in December 2008. Based on the current weather forecast and streamflow models, large creeks and rivers are expected to exceed bankfull conditions, with riverine flooding beyond traditional low-lying floodplain areas. Some local roads are likely to be affected by rising water levels as well.
There is a risk of ice jams with this event, as river flows are expected to rise quickly and move river ice. Ice jamming in the Lower Maitland River from Wingham through to Goderich should be expected.
Residents are reminded that due to warmer temperatures and accompanying rainfall, all ice should be considered unsafe. In addition, please use caution near all watercourses. Slippery and unstable streambanks, streambanks hidden by drifted snow, and extremely cold water temperatures will create additional hazards.
This message will remain in effect until 9:00 p.m. Tuesday, February 20, 2018, unless local conditions warrant an earlier update. Maitland Conservation will continue to monitor watershed conditions and will provide an update once actual rainfall amounts are recorded.
Jayne Thompson Communications Coordinator
Flood Duty Officer:
Steve Jackson, Flood and Erosion Safety Services Coordinator
Types of Flood Messages:
Watershed Conditions Statement – Water Safety – General watershed conditions are being assessed for high runoff potential that could lead to flooding, and to remind the public of general river safety issues.
Watershed Conditions Statement – Flood Outlook – Early notice of the potential for flooding based on weather forecasts calling for heavy rain, snow melt, high wind or other conditions that could lead to high runoff, cause ice jams, lakeshore flooding or erosion
Flood Watch – Flooding is possible in specific watercourses or municipalities. Municipalities, emergency services and individual landowners in flood-prone areas should prepare.
Flood Warning – Flooding is imminent or already occurring in specific watercourses or municipalities. Municipalities and individuals should take action to deal with flood conditions. This may include road closures and evacuations.