Watershed Conditions Update (flood bulletin, April 6-11, 2023)
WATERSHED CONDITIONS STATEMENT – WATER SAFETY
Issued April 6 at 15:30; Valid until April 11, 2023
Water levels in upstream areas of the Upper Thames River watershed are receding but will remain above normal over the holiday weekend. Water levels in London will peak later today before receding over the weekend. Current forecasts are for generally warm, dry weather over the next seven days, which will dry out the currently saturated ground.
The UTRCA’s flood control reservoirs at Fanshawe, Wildwood, and Pittock Conservation Areas are still being operated to reduce downstream flooding.
Parents are reminded to keep children and pets away from all watercourses. Banks adjacent to rivers and creeks are very slippery and, when combined with cold, fast-moving water, pose a serious hazard. Standing water can also present dangers. It is not safe to take shelter along riverbanks or in low lying areas that are prone to flooding.
Summary of Recent Events
Since March 16, the Upper Thames River basin has received approximately 115 mm of rain, resulting in four separate flooding events. On March 16, there was also approximately 75 mm of water content in the snow. The combined 21-day rain / snowmelt total of 190 mm has made this spring particularly wet. Of that 190 mm of water, approximately 140 mm made its way into the Thames River system.
Looking at historic data, 140 mm of runoff over a 21-day period corresponds to a 1:10 year event, which has a 10% chance of occurring each year. The last 1:10 year flood was in February 2018, which had less runoff but occurred over a much shorter time span and, therefore, resulted in higher peak flows and more flood damages.