The Ganaraska Region Conservation Authority maintains a flood forecasting and warning system. The purpose of the system is to reduce risk to life and damage to property by providing local agencies and the public with advanced notice, information and advice so that they can respond to potential flooding and flood emergencies.

A flood is defined as a situation where water levels in a watercourse exceed the channel banks. Flooding in Ontario is a fairly common occurrence. The greatest flood in recent memory hit the Port Hope area in March of 1980 when the Ganaraska River flowed over its banks as a result of heavy rainfall on a dense snow pack.

Rain on snow is not the only type of event that can cause flooding. Hurricanes moving north from the tropics can carry heavy rainfall into Ontario commonly resulting in flooding, particularly in larger watersheds. High local rainfall associated with severe thunderstorms can cause flooding usually associated with smaller watersheds.

Winter ice jams associated with spring break up have also resulted in severe flooding situations. High lake levels and/or storm surges on Lake Ontario can also result in flooding along the lakeshore.

Forecasting
The Ganaraska Region Conservation Authority operates its daily planning cycle to monitor, on an ongoing basis, weather forecasts, radar and watershed conditions at locations across the watershed. Water level and related information is remotely collected through an extensive network of stream gauges, precipitation gauges, snow course sites and staff gauges (monitoring network). Our extensive knowledge and historic data on the watershed's responses to extreme weather and conditions in our watersheds is used to develop a flood forecast.

When conditions warrant, GRCA will communicate with local agencies (municipalities, emergency services, local media, school boards and government agencies) issuing flood messages following a standard format used by all Conservation Authorities.

During spring snowmelt or severe storms, the Conservation Authority estimates the severity, location, and timing of possible flooding, and provides these forecasts to local agencies using one of the following message formats:

Watershed Conditions Statement  - Water Safety

Water Safety - High flows, unsafe banks, melting ice or other factors that could be dangerous for recreational users such as anglers, canoeists, hikers, children, pets, etc. Flooding is not expected.

Watershed Conditions Statement - Flood Outlook

Flood Outlook - Early notice of the potential for flooding based on weather forecasts calling for heavy rain, snow melt, high wind or other conditions that could lead to high runoff, cause ice jams, lakeshore flooding or erosion.

Flood Watch

Flooding is possible in specific watercourses or municipalities. Municipalities, emergency services and individual landowners in flood-prone areas should prepare.

Flood Warning

Flooding is imminent or already occurring in specific watercourses or municipalities.

Flood Event
Defined as a sudden increase in watercourse levels resulting from the occurrence of precipitation, snowmelt, or a combination of the two. The severity of flood events can range from minor increases in creek levels (resulting in “hazardous creek conditions”), to extreme flood conditions (posing a risk to life and property). These various types of events, and the corresponding flood response activities, are described in the Ganaraska Region Conservation Authority’s Flood Contingency Plan.

Flood Forecasting & Monitoring Stations

Station Name | Measured Parameters
Wilmot Creek (3rd Concession, Clarington) | Water Level, Rainfall and Water Temperature
Wilmot Creek (7th Concession, Clarington) | Water Level, Water and Air Temperature
Graham Creek (Newcastle) | Water Level and Water and Air Temperature
Ganaraska River (Sylvan Glen) | Water Level and Water Temperature
Ganaraska River (Osaca) | Water Level, Water and Air Temperature
Northwest Ganaraska River (Osaca) | Water Level, Water Temperature
Cobourg Creek (Cobourg) | Water Level, Rainfall, Water and Air Temperature
Cobourg Creek West Branch (Telephone Rd.) | Water Level, Water and Air Temperature
Baltimore Creek (Baltimore) | Water Level, Rainfall,  Water and Air Temperature
Ganaraska Forest Centre | Rainfall, Snowfall and Air Temperature, Soil Moisture and Temperature
GRCA Main Office | Rainfall, Relative Humidity, Wind Speed and Direction, Air Temperature, Soil Moisture and Temperature
Canton | Rainfall, Air Temperature, Snow Depth, Soil Moisture and Temperature