GETTING FLOOD READY BY MAY 2019
Thank you for registering for our dedicated flood readiness newsletter that will provide regular updates about our bold and sustainable climate adaptation plan to protect Drumheller from future flooding. We have begun working through the five phases of our Flood Mitigation and Climate Change Adaptation System and are seeing some significant progress. We are in the process of building a dedicated flood readiness website, updating our municipal response plan, and creating a comprehensive structural mitigation plan to determine the best permanent flood-mitigation solution for Drumheller. Experts are guiding us through this process over the coming months. Our aim is to be flood ready by May 2019, which doesn’t mean all structural changes will be completed (such as berms), but we are on the right track to take action as a community as early as this flood season.
The area at risk of future flooding in Drumheller is 100 km of riverbank which includes our neighbourhoods of Nacmine, Newcastle, Midland, North Drumheller, Central, Riverview, Rosedale, Wayne, Aerial, Cambria, Lehigh, East Coulee and Western Monarch, which can all be impacted by the Red Deer River, the Rosebud River and Michichi Creek. Over the coming months, this newsletter will inform residents about flooding and how to plan ahead and prepare for a flood, and how to take action when flooding occurs. This month, it is important to understand our history of flooding in Drumheller, the types of flooding that typically occur and the main causes of flooding in our community. If you havent’t yet registered for this newsletter you can do so by clicking here or call us at 403-823-6300.
Implementing our Flood Mitigation and Climate Adaptation System requires the engagement of the entire community including residents, local businesses and organizations. We are hosting our first flood readiness booth at the Sports, Recreation & Arts Expo on March 6 from 4pm to 7pm at the Badlands Community Facility. We hope that parents and kids will stop by to learn about flooding in Drumheller and participate in some flood-related activities. Please join us to see how we are changing the channel on flood readiness.
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OUR HISTORY OF FLOODING
The Town of Drumheller, like no other town in Canada, can tell tales of flooding and climate change since the ice age. The most serious flood we have experienced in the more recent past was on June 27, 1915 due to rain on snowmelt. We have since had significant floods in April 1948 (ice jam), in August 1954 (rainfall), in April 1997 (ice jam), in June 2005 (rain on snowmelt) and in June 2013 (rain on snowmelt). Many of these floods resulted in declaring States of Local Emergency (SOLE). Just recently, in the Spring of 2018, we had another SOLE due to an ice jam and high flow. The ice jam on the Red Deer River released without consequence. The high flow on the Rosebud River caused overland flooding in Wayne.
These historic flows causing flooding from rain on snowmelt typically occur the third week of June with ice jams often occurring in April. While Drumheller has braved many floods, we have luckily sustained little damage to our land and our core cultural heritage as the Dinosaur Capital of the World. That being said, science tells us very clearly that Drumheller will be subjected to more frequent increases in temperatures, higher amounts of precipitation, and an increased risk of extreme climates as a result of warmer temperatures, resulting in more seasonal floods from April through to June.
Below you will see a graph depicting the historic flow rates and height of flooding in the Drumheller Valley.
TYPES OF FLOODING
Overland flooding happens when water overflows the Red Deer River, Rosebud River or Michichi Creek banks due to rain or extensive volumes of melted snow. This is a type of flood that results from the level of water outside of your dwelling rising, allowing water to enter your home.
When the Red Deer River, Rosebud River or Michichi Creek rise, water can flow back into the stormwater pipe system. Water may spill back onto streets or basements through stormwater drains.
Water on flooded streets or high groundwater may drain into the sanitary sewer system. This overloads the sanitary sewer pipes and can force sewage back through the sewer line and into your basement.
MAIN CAUSES OF FLOODING
ICE JAMS (Frozen Water)
These result from accumulation of ice fragments that build up to restrict the flow of water causing a temporary obstruction. They form during the freeze-up and break-up periods, the latter having the greater flooding potential in Drumheller valley.
RAIN ON SNOWMELT (Flowing Water)
Most of the precipitation in winter is stored as snow or ice on the ground. During the spring melt, huge quantities of water are released causing a freshet, which is heavy spring runoff and flooding. When the ground is frozen, melting snow is unable to penetrate and runs off over the ground surface into the Red Deer and Rosebud Rivers and Michichi Creek. Flooding is a greater concern when rising snowmelt is compounded by runoff from heavy rainfall. The later the thaw, the more likely flooding can occur. This type of flooding in Drumheller typically occurs in late June.
RAINFALL (Falling Water)
Flash floods usually happen on small watersheds as a result of a torrential downpour, often caused by heavy thunderstorm activity. They are characterized by the occurrence of the peak of the flood within six hours of the onset of rainfall and can be extremely dangerous. The flood conditions develop rapidly because the rainfall is so heavy the ground is incapable of absorbing the water quickly enough, resulting in a very high runoff rate.