Understanding Flood Forecasting
- Why does flooding happen?
- The effects of climate change
- Types of Flood Warnings
- Understanding Watershed Conditions Statements
Why does Flooding happen?
The majority of flooding happens when excess water events occur in low-lying areas, such as much of the Essex region. Flooding events occur from a variety of overlapping factors.
Over the last two winters, snowmelt from the upper great lakes has caused the levels of Lake St. Clair and Lake Erie to rise to record levels. Strong winds can push lake waters against the shoreline, preventing rivers and watercourses from draining. This is especially true of old, low-lying watercourses close to buildings and other structures, such as those that were built prior to ERCA’s regulations. Such activity also increases erosion. Impermeable construction (buildings, pavement, etc) prevents water from draining into the ground. This rapid runoff can overwhelm rivers, watercourses, and municipal drainage systems.
When these events occur simultaneously or over an extended period of time, long-term flooding can occur.
Climate change has exacerbated high water levels and flooding effects.
While modelling and future predictions are uncertain, the evidence points to increasing variability and unpredictability of lake levels. In other words, heavy rain is likely to get heavier.
While climate change may not increase the overall number of storms, there will be a rise in the number of intense storms as well as how often these intense storms happen, particularly in the winter and spring. Extreme weather is costly. Storm cleanup costs, insurance rates, and business disruption are expected to increase with the wilder weather, with less time between storms for effected areas to recover.
Types of Flood Warnings
Watershed Conditions/Safety Bulletin
Factors could be dangerous, but flooding is not expected.
Early notice of flooding potential based on weather forecasts.
Potential for flooding within specific watercourses or municipalities. Municipalities, EMS and landowners in flood-prone areas should be prepared.
Flooding is imminent or is occurring in specific watercourses or municipalities.
Understanding Watershed Conditions Statements
- Watershed Conditions –
- 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 –
- 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 Bulletins:
- Flooding is possible in specific watercourses or municipalities. Municipalities, emergency services and individual landowners in flood-prone areas should prepare.
- Flood Warning Bulletins:
- Flooding is imminent or already occurring in specific watercourses or municipalities.