Flooding can occur at any time in Calgary, although the period between May 15 and July 15 is when we are most likely to experience flooding. Historically, this is when we experience our largest rainfalls.
Flooding in Calgary can happen in several ways:
- Rivers and streams cannot contain excessive rainfall within their banks.
- Rain and snowmelt cannot be absorbed into the ground.
- Waterways or storm drains become blocked with debris or ice.
- Water containment systems, such as stormwater or sewage pipes, are overloaded or break, causing backup.
- Severe thunderstorms cause localized flooding of streets and property.
- Ice jams on rivers may cause elevated water levels and overland flooding.
The speed with which flooding is experienced varies. Calgary sits at the confluence of two large rivers, the Bow River and the Elbow River, and several small creeks. The Bow River has a large watershed drainage area and drops from the mountains to the city at a steep slope. The Elbow River also drops in elevation at a steep slope and has a relatively short trip from the mountains to where it meets with the Bow River in the heart of Calgary.
The consequence of having two short and steep river systems is that any impacts, such as fast and high flow rates, can reach Calgary at a rapid speed with little warning.
Weather conditions can also change rapidly. Calgary’s proximity to the Rocky Mountains makes accurate weather forecasting a challenge. Weather forecasters have a tough time predicting how weather systems will behave once they reach conditions surrounding the mountains.
Generally, winter storms follow a more predictable pattern, allowing more advance warning time so that you can take appropriate actions. Summer weather patterns can be much more volatile. When you are monitoring the weather, you may also hear alerts related to the river. If you live in the flood plain or in low-lying areas, it’s important to understand what the alerts mean so you can be prepared and take action.
The first step towards protecting yourself is knowing your flood risk and the sources of information available to you:
- Visit ca/floodinfo to determine your flood risk, and for detailed information on how you can be prepared for flood season. You can also download a copy of the Flood Readiness Guide.
- Prepare your 72-hour emergency kit. This kit holds supplies to support you and your family for three days in an emergency situation.
- Visit Alberta Environment’s river basin website and download the river monitoring app by searching for “Alberta Rivers” on your device.
- Listen for and sign up for Alberta Emergency Alerts (AEA). Alberta Emergency Alerts interrupt local broadcasting. As well, you can download the AEA app to a smart device to receive notifications.
The City of Calgary – Preparing for flood season
The City of Calgary’s priority when planning for and responding to flooding is to protect its citizens, critical infrastructure, civic property, the environment and the economy.
The City prepares annually for flooding by:
- Working with the Government of Alberta to monitor snow pack, rainfall and temperatures, as well as river flow levels in the mountains and foothills.
- Developing and maintaining emergency response plans.
- Conducting training sessions and exercises for City personnel.
- Identifying those areas of the city and critical infrastructure that are most vulnerable to flooding.
- Ensuring adequate emergency resources are in place.
- Sharing information with Calgarians, businesses, stakeholders and other municipalities.
- Operating existing infrastructure, such as dams, reservoirs and outfall gates, to reduce flow rates and mitigate flood damage.
The City strives to maintain all critical business functions and services to Calgarians during any emergency or disaster including flooding. The City does not typically protect individual private properties from flood risk. Property owners remain responsible for protecting their property. Please visitcalgary.ca/floodinfo for information on how you can be prepared for flood season.