Southwestern Ontario is currently experiencing a warm spell with a large amount of rainfall. Temperatures yesterday were around 5 C during the day and are expected to reach 15 C today. Temperatures aren’t expected to fall beneath freezing until overnight tomorrow. Since the rainfall began yesterday, the watershed has received between 20 and 40 mm of rainfall. Weather forecasts are predicting that as much as 35 mm of additional rainfall may appear before the rain ends. There is also the chance of thunderstorms with this weather system. Before this warm up, there was approximately 40 mm of water stored in the snowpack in the Upper Thames watershed and around 25 mm in the Lower Thames watershed. With the warm temperatures and rain, almost all the snow is expected to melt and add to the runoff.
The heavy rains alone may lead to localized flooding in areas with poor drainage. Water levels on the smaller local watercourses in the Lower Thames rose rapidly yesterday and many are near bank full conditions or have spilled their banks. Water levels on some of the larger systems, such as McGregor Creek are still rising and will continue to rise with today’s additional rain. The prolonged rains will keep water levels high through Thursday. Some local watercourses still have snow and ice accumulations that could block flows causing water to back up and leading to greater flooding. The Lower Thames Valley Conservation Authority is currently operating the Indian-McGregor Creek Diversion Channel to protect the south end of the City of Chatham from flooding.
The Thames River will also rise and is expected to reach levels not seen in a decade. Peak water levels in the City of London are expected late Wednesday and will work their way downstream over the next few days reaching the Thamesville and Chatham areas late Friday or early Saturday. All along the Thames River from Delaware to Chatham, the low lying river flats will be flooded and in some areas could reach the upper table lands. Through Middlesex and Elgin Counties there could be flooding issues around bridge crossings and water will back up local watercourses. Revised forecasts suggest that flooding in the community of Thamesville is quite possible. In the City of Chatham basement flooding for those businesses backing onto the Thames River along King St. is expected. There is also expected to be flooding on some of the low roads adjacent to the Thames such as Siskind Court, the area around William and Water, Salter and the low portion of Thames St along the river. Water levels in the downstream areas can be expected to remain high all through next weekend. Currently water levels are expected to be similar to those observed during the 2008/2009 flood of the Thames River. If the higher rainfall amounts appear, there is a chance that Thames River water levels in the City of Chatham could be even higher, closer to those observed in 1985. The Lower Thames Valley Conservation Authority will be operating the 6th Street Backwater Dam and Pumping Station in downtown Chatham to protect the low lying portions of the city upstream on McGregor Creek.
Ice cover on the Thames River has degraded and the river is largely open upstream of Little John Road in Chatham-Kent and through the City of Chatham down to nearly Prairie Siding. The remaining ice cover will melt, break up and move downstream. With the warm conditions and rain, the remaining ice isn’t expected to have enough strength to cause any significant ice jams. However, it could cause flow restrictions leading to elevated water levels in the areas of accumulation. This was happening around Thamesville earlier today but that ice has now moved down to the Kent Bridge Area.
Residents with properties that back onto watercourses and the river should secure their properties and remove any items that could be damaged by flooding or get loose and become floating debris. Attempts should also be made to ensure that catch basins and other drainage works are free of debris and can function properly.
People should take extra caution and avoid the river, ditches, and streams. The combination of slippery banks, broken up or degraded ice, and fast moving cold water can be dangerous. Standing water can also present its own unseen hazards. Children, pets and livestock should be kept away from the water.
Officials will continue to monitor the situation and update this advisory if necessary.
This message will be in effect until February 22nd, 2018.
Contact: Jason Wintermute (email@example.com, 519-354-7310 x227) regarding this message.