Wet Week in July
The Upper Thames River watershed has had an unusually wet July. On July 10, the remnants of Hurricane Beryl reached southwestern Ontario, dropping 40-90 mm of rain across the watershed. UTRCA staff operated the flood control dams at Fanshawe, Pittock, and Wildwood Conservation Areas to minimize downstream flooding by storing water in the reservoirs. At Fanshawe, the rising reservoir encroached on the campground. A few campers were moved to new sites and some unoccupied sites were closed for the weekend.
Harris Park, July 17, 2024
By July 15, when round two of the wet weather started, watercourses were returning to typical summer flows but the ground was still fairly saturated. That morning, the London area was hit with severe storm activity, with some City rain gauges measuring as much as 75 mm of rain in less than two hours. The intense rainfall overwhelmed urban drainage systems in many areas, leading to flooded streets and basements.
The severe weather continued the following day, triggering a heavy rainfall warning from Environment and Climate Change Canada. The storms were mostly in rural areas north and east of London, and the intense rainfall on saturated ground caused widespread flooding of agricultural fields and high runoff into streams and rivers.
UTRCA鈥檚 water management, conservation areas, and communications staff were kept busy, with round-the-clock monitoring of watershed conditions, frequent operations at the flood control structures, impacts at all three parks due to the high reservoir levels, and multiple flood bulletins going out to municipal flood coordinators and other partners.
By July 17, all three of the UTRCA鈥檚 flood storage reservoirs were filled to much higher levels than what is typical in the summer. Once again, campers were relocated at Fanshawe, the day-use and some overnight campsites were flooded at Pittock, and the boat docks at Wildwood were under water. While the dam operations greatly reduced flows downstream, there was minor downstream flooding in flood plain areas including Harris and Gibbons Parks in London. In Woodstock, Dundas Street was closed due to flooding, and part of the St. Marys Golf and Country Club was under water.
Discharges from the structures continued to be higher than normal for several days following the flood, as water management staff gradually brought the reservoirs back down to typical summer levels.
In total from July 10-17, the watershed received an average of 140 mm of rain, ranging from 76-197 mm. While a flood of this size would be pretty typical in the聽 early spring, it is quite rare in mid-summer when parks located in floodplains are being used for recreational purposes. As well, in the spring, the Pittock and Wildwood reservoirs are at their low, winter level and have ample flood storage, whereas in July, they are at their higher, summer level with less storage capacity and the conservation areas are busy with campers and day-use visitors.
Contact:
Mark Helsten, P. Eng., Senior Water Resources Engineer