Floods

Flooding is considered the most significant natural hazard in Ontario in terms of death, damage and civil disruption. Ontario has a history of severe flood events, including 1954 with the devastating Hurricane Hazel flood that caused 81 deaths and estimated to have caused $133 million in damages.View the current Flood Monitoring message.

In response to flooding, Ontario enacted legislation to create Conservation Authorities who were charged in part with the responsibility for mitigating the impact of flooding and for protecting human life and property from flood damage.

A flood is an overflowing or influx of water beyond its normal confines. Floods can occur at any time of the year and are caused by heavy rains, excess snowmelt, spring break-up and ice jams, wind related storm surges across large lakes, or the failure of dams. Areas that are vulnerable to flooding are called flood plains or hazard lands.

Flooding can cause death and devastating losses to communities including homes, property and infrastructure. Flood warnings reduce the risk of these losses.

MNR provides a Flood Forecasting service through the Surface Water Monitoring Centre (S.W.M.C).MNR and conservation authorities use streamgauges, weather stations, snow conditions, meteorological forecasts and computer models to determine the potential for flooding. This is called flood forecasting. When an agency has determined a flood is possible, the warning process begins.
 

FLOOD ADVISORIES

Advance warning of an impending flood allows municipalities and other government agencies to put emergency response plans into operation, to evacuate communities and remove portable property from floodplains and flood-susceptible areas. Advance warning notifies the public of developing or ongoing unsafe river and lake conditions, and allows them to take precautions.

Conservation authorities and MNR District offices (in areas where conservation authorities do not exist) issue the following flood messages to local municipalities and the media. Local governments are then responsible for communicating messages to the public and for first-line emergency response. These messages may be issued at any time of the year.

FLOOD ADVISORY: notifies that the potential for flooding exists within specific watercourses and municipalities.
FLOOD WARNING: notifies that flooding is imminent or occurring within specific watercourses and municipalities.
FLOOD SAFETY BULLETIN: notifies that unsafe lake, river and channel conditions exist.
WATERSHED CONDITIONS BULLETINS: notifies of anticipated watershed conditions.