Toronto and Region Conservation Authority (TRCA) issued a Shoreline Hazard Warning on April 30, 2019 in response to rising water levels in Lake Ontario. Later the same day it issued a Watershed Conditions Statement in advance of the anticipated rainfall that is expected in the GTA over the next few days.
Water levels in Lake Ontario are rising quickly and are expected to continue rising until late May or early June. Properties along the Lake Ontario shoreline and on the Toronto Islands could begin to experience the effects of flooding. Large waves may exacerbate erosion and flooding.
TRCA has been working with City of Toronto staff since last week to address potential impacts, providing assistance and guidance by forecasting and updating local conditions, identifying and monitoring at-risk shoreline areas and providing risk mapping. TRCA is also deploying staff and resources to prepare for high water levels on Toronto Islands by setting up pumps and sandbags, and monitoring other shoreline areas. Staff will be deployed as needed, over the coming weeks to assist with response operations. Our collective response to this event is benefitting from the lessons learned and plans developed in response to the 2017 high water event.
Lake Ontario water levels are influenced by several factors, including water flowing in from Lake Erie and runoff from the watersheds that drain into Lake Ontario. Water flowing out of the lake is controlled at Moses-Saunders Dam near Cornwall, by the International Lake Ontario-St. Lawrence River Board (ILOSRB). In regulating water flowing out of Lake Ontario, the ILOSRB must balance risks associated with areas downstream of the lake. The ILOSRB has decreased flows from Lake Ontario to minimize flood risks along the St. Lawrence River. The combination of reduced outflows from Lake Ontario, high inflows from Lake Erie, and continued runoff from surrounding watersheds is the reason Lake Ontario levels are expected to continue rising.
Residents are reminded to avoid and/or exercise caution around all Lake Ontario shoreline areas. Use extra caution when around any water bodies, and stay away from any areas experiencing erosion or any areas that are flooded.