High water levels prompt hazard mapping update
With Erie and St. Clair at all-time highs, strong winds elevate risk of flooding
Updates to 43-year-old shoreline flood and hazard land mapping are in the works for Essex County as a response to record-high lake levels recorded last month.
Essex Region Conservation Authority board members Thursday evening approved the completion of watershed-based flood-risk assessments, a first step towards revisiting hazard land mapping created in 1976.
“Our current static lake levels are almost at the peak of some of the severe events that occurred in April,” James Bryant, ERCA’S water resources engineer, told the board. He presented to them a report on recent and historic flooding and lake levels. “If those same events occurred now, the impact would be critical.”
Water levels in both Lake Erie and Lake St. Clair set a new record with their May monthly averages, which surpassed previous records from 1986 by about 12 centimetres. From April to May, Lake St. Clair has risen by 19 cm, and Lake Erie by 22 cm.
Current lake levels are exceeding all-time highs. Lake Erie sits 6 cm higher than the June 1986 high of 175.04 metres.
“It’s crucial to understand the level of risk at stake for some of these municipalities,” said Bryant.
Although ERCA continues to monitor conditions and issue flood advisories, Bryant’s report concluded current water trends indicate a need to further investigate and complete watershed-based flood-risk assessments in collaboration with municipal partners in the area. From Jan. 1 to May 31, ERCA issued a total of 29 advisories — those include watershed condition statements, flood watches and flood warnings. In the same five-month period in 2015, only three advisories were issued.
“We essentially have to remain in that long-term flood watch until conditions improve,” Bryant said, noting that, at the time of the meeting, a flood watch had been in effect for four days.
The area most impacted by lake levels has been east Leamington, and, more specifically, the shoreline between Point Pelee National Park and Wheatley. Because of high water levels, flood events are occurring and have the potential to occur from much lower wind speeds from any direction, Bryant’s report stated. This, combined with shoreline infrastructure that has been weakened from multiple years of wave action and high waters, results in greater risks to shoreline communities.
Flood events and elevated lake levels have caused “significant” erosion, which has damaged infrastructure in Leamington and Pelee, the report said. Cotterie Park in Leamington experienced a “complete washout” in April 2018, and, although repairs were completed there, was further damaged by shoreline flooding in May of 2019.
Pelee Island was able to make emergency repairs to its affected areas, but the severity of erosion now surpasses the capabilities of repair and maintenance equipment.
“There’s no question that this spring has been challenging all around,” said board chair Irek Kusmierczyk, also a Windsor city councillor. He noted high water levels have prompted the closure of Amherstburg’s Holiday Beach. Flooding has delayed ERCA’S tree planting initiatives in places where machines are needed to do the job.
Boat slips at Windsor’s Lakeview Park marina were closed for the season due to high water levels in mid-may.
All of the flood events so far this year have been caused by an initial elevated lake level, followed by wind and wave action overtopping breakwalls, Bryant’s report found.
ERCA has ben assisting the municipalities with flood planning and repair. In Leamington and Lakeshore, the organization has helped prepare reference guides to address flooding risks in the area. It plans to complete hazard mapping along the shoreline there. ERCA has also helped the City of Windsor prepare terms of reference for the Sandwich South Master Services and Little River Watershed Flood Plain Mapping project.
As for the coming months, Bryant indicated to board members that other organizations, like Climate Change Canada, are underestimating future water levels in their forecasts.
“What we’re seeing now are potentially record setting levels into fall.”