Tuesday, May 16, 2017

Flood season: understand, be prepared and stay informed

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 widespread rainfalls.

How does flooding occur?

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.

Calgary sits at the confluence of two small rivers, the Bow River and the Elbow River, and several smaller 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 so it is a relatively short trip from the mountains to where it meets with the Bow River in the heart of Calgary.

Having two short and steep river systems means that fast changes to high flow rates can reach Calgary rapidly 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.

What we’re doing to prepare

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:
  • 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 cannot prevent or mitigate all flood risk to all private properties. Property owners remain responsible for protecting their property.

What you can do to prepare

The first step towards protecting yourself is to know your flood risk and the sources of information available to you:
  • Visit calgary.ca/floodinfo to understand 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.

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