Town of Canmore
Mountain Creek Hazard Mitigation Issue 4 l October 2014
A flood retention structure similar to this is proposed for long term mitigation in Cougar Creek. Photo courtesy of alpinfra consulting + engineering gmbh, current construction site in Austria.
Moving Forward... After the flooding last summer, the Town created a Mountain Creek Hazard Mitigation Program. One element of this program was to get short-term mitigation in place in time for 2014 spring run-off. This was completed in most of Canmore’s mountain creeks by May 2014. Another element of the program is to better understand the hazards and risks associated with debris floods and debris flows. The key results of the Mountain Creek Hazard Mitigation Program are: • Stakeholder Alignment
– Ongoing community communications and partnering with key stakeholders • Hazard Assessed
– Forensic study and hazard mapping and return period and magnitude analysis • Risks
Understood – Community wide safety risk analysis and infrastructure and property inventory • Successful Active
Mitigation – Funding, permitting, approvals for short and long term infrastructure
• Successful
Passive Mitigation – Emergency planning and preparedness and updating municipal and provincial policy Our focus now is turning to long-term mitigation. While significant work has been done on many creeks, Cougar Creek being the most dramatic, the work completed to date was meant to protect against an event of similar size of the 2013 event. So much good work was done that it might seem like the mitigation work is complete. However, we’ve learned in the last year that even larger events have occurred in the past and could occur again in the future, so we need to install infrastructure to protect our community against the risks associated with a larger event. Ultimately, our end goal is an acceptable level of protection against all hazards. Right now, our focus is on mountain creeks. We do have other risks in our community including wildfire, river flood, proximity to dangerous goods routes, and severe weather. Town staff are working to be prepared for and mitigate against all known community risks. This issue of the newsletter explains how we will work with the community to create long term mitigation to protect against future debris floods and debris flows on our steep mountain creeks.
canmore stands strong canmore stands strong
2 Town of Canmore Mountain Creek Hazard Mitigation
Cougar Creek Hazard Maps Our geo-hazard investigations after the 2013 flood taught us that much bigger events have occurred in Cougar Creek in the past. There is a 10%-30% chance that a debris flood event of any size, from small to large, will occur any given year.
The maps shown here were created by BGC Engineering Inc. For more information see the following reports located on the Town’s website:
We are starting our long-term mitigation work in Cougar Creek because the hazards in that area are the most significant of all the creeks in Canmore. Over 4,000 residents and 1/3 of our business community are located in Cougar Creek. It is incumbent upon the Town to provide the community with a complete understanding of the hazards we face and to address these to the very best of our ability.
BGC Engineering Ltd. (2014) Cougar Creek Debris-flood Risk Assessment
The current short-term mitigation will provide protection only for small to medium sized events. The debris nets and articulated mats will reduce the impact of larger events, such as the one that occurred in 2013, but will not fully contain it. Debris floods that overwhelm the existing mitigation pose a danger to large areas of the Cougar Creek fan. The resultant risk to safety and property is not acceptable. We are working with experts from Austria where government and industry have been successfully managing hazards from creeks similar to Cougar Creek for decades, using tested and proven designs. A long-term mitigation structure is being designed to bring the hazards in Cougar Creek to a more acceptable level (see map #3).
BGC Engineering Ltd. (2014) Cougar Creek Debris-flood Hazard Assessment
HAZARD ZONE CHARACTERISTICS Very fast flowing and deep water and debris. High likelihood of severe building structure damage and severe sediment and water damage. Extremely dangerous to people in buildings, on foot or in vehicles. Fast flowing and deep water and debris. High likelihood of moderate to major building structure damage and severe sediment and water damage. Very dangerous to people in buildings, on foot or in vehicles. Potentially fast flowing but mostly shallow water with debris. Moderate likelihood of building structure damage and high likelihood of major sediment and/or water damage. Potentially dangerous to people on the first floor or in the basement of buildings, on foot or in vehicles. Slow flowing shallow and deep water with little or no debris. High likelihood of water damage. Potentially dangerous to people in buildings, on foot or vehicles in areas with higher water depth.
HAZARD MAP FOR EVENT SIMILAR TO 2013 FLOOD (100-300 YEAR RETURN PERIOD) The probability of an event of this size happening in an average lifetime is approximately 70%
canmore stands strong canmore stands strong
Town of Canmore Mountain Creek Hazard Mitigation 3
HAZARD MAP FOR EXTREME EVENT (1,000-3,000 YEAR RETURN PERIOD) The probability of an event of this size happening in an average lifetime is approximately 7%
HAZARDS WITH PROPOSED LONG TERM MITIGATION INSTALLED
canmore stands strong canmore stands strong
4 Town of Canmore Mountain Creek Hazard Mitigation
Overview of Risk The terms hazard and risk are often used interchangeably. They are, however, two distinct things. In simple terms, a hazard is something that has the potential to cause harm or damage. Risk is a measure of the probability and severity of the hazard to cause harm. As we work toward long-term mitigation options, understanding the distinction between hazard and risk becomes important. The maps on the previous pages show the hazards, posed by Cougar Creek for two different return periods. In evaluating mitigation options, we clearly need to reduce the hazard in this area. To do that well, we also need to understand the risk. Due to the presence of development this hazard would result in major damage and likely loss of life.
As a society we are appropriately upset by incidents that cause many simultaneous fatalities. For example, think of the difference in media attention between loss of life in a car crash, where one individual or family is affected, and a plane crash were hundreds are affected. Anytime there is a risk where multiple lives could be lost, our risk tolerance is decreased. When possible, a community should reduce a known risk of multiple fatalities to “As Low As Reasonably Practicable” (ALARP). Many countries have developed systematic ways to address this risk to group life. Data is used to measure the frequency of events leading to loss of life and the expected number of lives lost. This system has been used in Canada, the United States, the UK, Australia, and Hong Kong. We are using the same systematic approach, the Canadian Standards Association Risk Management Guidelines, in our long term creek mitigation work in Canmore.
SOCIETAL RISK FREQUENCY (F) OF FATALITIES (per year)
How much risk an individual is willing to take is a personal choice. Investing in the stock market, skydiving, and driving a car are all examples of risks that some of us choose to take and others choose to avoid. For something like mountain creeks, it’s no longer a personal choice. We have to measure risks as a community. Generally, a community risk should be less significant when compared to the risks of average individuals in everyday life. One typical risk in average daily life includes the possibility of dying in a motor vehicle accident. This is a risk we choose to live with everyday. We are working to reduce the risk in Cougar Creek so that it is similar to the risks general society chooses to live with everyday.
1/1 1/10
UNACCEPTABLE
1/100 1/1,000 1/10,000
ALARP
1/100,000 1/1,000,000 1/10,000,000
1/1,000,000,000
INTENSE SCRUTINY REGION
BROADLY ACCEPTABLE
1/100,000,000 1
10
100
1,000
10,000
NUMBER (N) OF FATALITIES Cougar Creek currently fits into the Unacceptable portion of this chart.
canmore stands strong canmore stands strong
Town of Canmore Mountain Creek Hazard Mitigation 5
Risk Assessment Process in Canmore Government has an obligation to understand and mitigate as appropriate the risks to our community. The process we are using to do this is: Systematically identify Canmore’s mountain creek hazards, their likelihood and consequences (ongoing over the last year) •
•
Review risk tolerance criteria established by experts (ongoing over the last year) •
Estimate risks and compare against acceptance criteria (ongoing over the last year) •
Host public information sessions
•
Present council and stakeholders with recommendations for mitigating risks •
Work with partners on needed funding agreements, permitting and approvals In Canmore, we have determined that the greatest risk for an alpine torrent is in Cougar Creek and its alluvial fan, due to the significant amount of development in the area (see page 2-3). Our minimum goal
is to reduce the risk of death for any given individual in any given year to as low as reasonably possible (see page 4). We also need to reduce the potential economic risk. As we work through mitigation options, we are considering the cost/ benefit comparison to investment in mitigation infrastructure. Direct damage to property and infrastructure is estimated to be an average of $700,000/year without mitigation. The annualized costs of the current hazard will be compared to the costs of mitigation. Though cost won’t be the only factor considered in determining an appropriate mitigation scheme, it will be a significant consideration. This fall, we will be inviting the community to learn about how we are planning to reduce the risk in Cougar Creek to a more acceptable level. We have examined the implications of several built structures that provide options for capturing debris and sediment and possibly even capturing flood waters in Cougar Creek. An analysis of the options that determines the acceptable level of community risk along with other criteria including impacts on environment, cost, and safety will be presented to the community.
Risk Assessment Process Hazard Identified Affecting New or Existing Project
Cougar Creek Long Term Mitigation Tentative Time Line October 2014 Community consultation and finalize long term mitigation option November 2014 Mitigation option and capital project approval by Council
Characterize Hazard Estimate Risks
Are Risks Tolerable?
Revise Project Scope
NO
Develop Risk Control Options
YES Accept Risks
YES
Are Mitigated Risks Tolerable?
NO
Winter 2014 - 2015 Detailed design of long term structure(s) Spring 2015 Public Tender for construction Summer 2015 - Fall 2016 Construction of long term mitigation structure(s)
canmore stands strong canmore stands strong
6 Town of Canmore Mountain Creek Hazard Mitigation
Other Creeks and the Bow River
Stoneworks Creek
Stone Creek
Engine Bridge
Of course, Cougar Creek is not the only mountain creek or flood risk in Canmore. While it is the most developed creek, we have eight other mountain creeks in our community and the Bow River. We are beginning this systematic process of understanding and evaluating risk with Cougar Creek. Next, we will complete hazard and risk assessments for other creeks and work with our partners and the community to determine approaches to reducing risk where it is deemed unacceptable. A similar approach will be employed for the Bow River, where the system of dykes constructed by the Province is intended to provide protection for a 1:100 year return period flood event. Areas with significant development and possible social and economic impact are the main criteria for determining which creek is the next priority. From there, we will work through the very same process, until all developed creeks and the Bow River have been addressed.
Three Sisters Creek
On the Bow River, we have, in the last year, completed two inspections of the dykes with the Province of Alberta. High level modelling has been completed recently confirming the capacity of the Bow river has not decreased in the decades since the dyke system was created. A variety of ways to obtain data are being used to create models of the Bow River. In addition to traditional methods (physically surveying the river bottom) we have also worked with a company which uses unmanned aerial vehicles (drones) to fly the Bow River to collect aerial photographic topographic information as well as bathymetric elevations of the river bottom. Additional data includes bare earth elevation models of the river valley from the Province’s LIDAR images taken last September. All of this information is being used to establish the current geometry of the river and compare with the geometry of the river at the time the Province developed their hydraulic models of the river and built the protection dykes.
canmore stands strong canmore stands strong
Town of Canmore Mountain Creek Hazard Mitigation 7
Bow Valley Wellness, Recovery & Preparedness Helping each other in challenging times
Moving through recovery and onto wellness... Since the summer of 2013 The Bow Valley Wellness, Recovery and Preparedness Committee has strived to develop, coordinate and promote programming to support members of the Bow Valley community impacted by the flooding. Since its inception the following supports have been offered to the community, reaching well over a thousand residents in impacted neighborhoods, through workshops, information sessions, respite camps at Chief Hector, sharing health information, and on-going individual support through and Community Helpers program, the Red Cross door knocking campaigns and various counselling supports.
As a year has passed, the committee will begin to explore ways to promote ongoing wellness in new and innovative ways to build on our resilience as a community. Still, it is important we recognize aspects of recovery are very personal which we all move through in our own way and at our own pace. It is our hope this next year will bring with it new opportunities to create engagement at the community level, while offering ongoing programming to help all move through recovery and onto wellness.
Check us out on Facebook under “Bow Valley Wellness Committee�. If you need assistance, please contact us at 403.678.4696.
canmore stands strong canmore stands strong
8 Town of Canmore Mountain Creek Hazard Mitigation
One Local’s Story William “Bill” Cherak and living on the Bow River “ The water was so high in my yard that it came up over my bird bath which is 30 inches tall. My neighbours wood pile floated down to my house. Thank goodness for my good friends, they came over and helped me sandbag or things would have been much worse.” Born and raised in the Bow Valley, I’ve been around long enough to see some flooding and high water on the Bow River. I live right along the river and my house is located in a low spot, where the path and the berm don’t extend, so when the river starts to rise, my house is the first one at risk. During the flood of 2013, while everyone else was focused on Canmore’s creeks, I was watching the Bow. When the Canmore mine closed, a culvert that the old mine train track used was plugged. There used to be brown trout across from the old Cochrane mine, but with that plugged culvert, the trout weren’t there anymore. That changes the way the river flowed and caused a lake to form in front of my house. It’s been like that every year since. I was one of the founders of the Canmore golf course. We have had issues at the 5th hole with river flooding so we had a map drawn up of the high water level. The golf course, the berm and the path by my place are on Crown land, so there’s not much the Town can do, but at least we know where the high water marks are and when we should start to prepare. In past years, a friend would come and set up a tarp system in my yard every year. It helped to prevent water from coming into the house. Unfortunately for me, that person retired and moved away before the 2013 flood, so I didn’t have the tarp system in the year I needed it most.
Bill Cherak’s back yard. The bird feeder is barely visible to the right of the flag.
After watching the river rise year after year, I’ve gotten kind of used to it, so I don’t necessarily worry in the spring when the river comes up. 2013 was different though. That’s the highest it’s been in my memory and I was getting very concerned. The water was so high in my yard that it came up over my bird bath which is 30 inches tall. My neighbours wood pile floated down to my house. Thank goodness for my good friends, they came over and helped me sandbag or things would have been much worse. The water got as high as a 27 inch mark on my door. I had two inches of water in the house. We had to take everything up from the basement level. This is the 5th or 6th time we’ve had water in the basement, but it’s the worst damage we’ve had. We had to remove the parquet flooring and rip out walls and insulation. It took my friends and me about two and a half months, after the water receded, to get the house back in order. I know the Town and the Province are looking at ways to protect my property and everyone who lives on the river. I’m really thankful for these efforts.
www.canmore.ca
canmore stands strong canmore stands strong