A Watershed Moment: the November 15, 2021 flood in the Coldwater River

An atmospheric river (AR) brought two days of intense rainfall to southwestern British Columbia (BC) on November 14, 2021. This rainfall resulted in extreme streamflow the following day on November 15 and extensive flooding and river planform changes in watersheds across numerous rivers in the lower Fraser River watershed, including the Coldwater River at Merritt. Numerous infrastructures, notably roads and bridges, were destroyed or inoperable. This destruction led to a near complete isolation of the Lower Mainland from road and rail access.

ARs are long, conveyor belts of warm, moist air that typically result in intense rainfall during the late fall and early winter. AR-related floods are generally larger than non-AR-related floods in coastal watersheds in BC. During the November 14, 2021 AR, the streamflow generated by rainfall was augmented by melting snow, associated with a rapid rise in temperature.

Following the November 15, 2021 flood, an urgent need emerged to estimate the peak flow of the Coldwater River to inform long-term reconstruction and mitigation efforts. In support of ongoing programs and recovery from November 15, 2021 flood, BGC was retained by several interested parties to complete hydrotechnical hazard and risk assessments and flood hazard mapping in the Coldwater River and Nicola River watersheds.

Time series of Nasa satellite images over the November 12 to 16, 2021 with Merritt, BC labels with the red pin. The Coldwater River watershed considered in this study is located upstream of Merritt.

We developed a flood frequency-magnitude relationship for the Coldwater River at Merritt by combining statistical models for AR-related and snowmelt-related peak flows. BGC’s current best estimate of the 200-year (0.5% Annual Exceedance Probability [AEP]) flood event is 445 m3/s (90% confidence interval 240 m3/s to 980 m3/s) calculated using peak flows recorded over the 1965 to 2021 period at the Coldwater River at Brookmere (08LG048) hydrometric station. To account for climate change, the peak flow distributions (AR-related and snowmelt-related) in the Coldwater River were scaled to account for the trends in rainfall-related (AR and non-AR) and snowmelt-related peak flows as projected by the Pacific Climate Impacts Consortium (PCIC). The climate-adjusted 200-year (0.5% AEP) flood event was estimated to be 730 m3/s (400 m3/s to 1600 m3/s for the 90% confidence interval) assuming a 75-year future time horizon from present. This estimate corresponds to a 64% increase compared to the stationary case (445 m3/s).

These findings show that climate change effects are profound and will influence the design of flood protection structures, flood construction levels (FCLs), and the design of infrastructure alongside or crossing watercourses.

Click here to view a copy of the draft report for this work.

Melissa Hairabedian, M.Sc., P.Geo. (BC, ON)

Hydrologist

Melissa is a senior hydrologist with expertise in hydrotechnical hazard identification, assessment, and management. Her interdisciplinary academic background and professional consulting experience reinforce her comprehensive set of technical skills including statistical hydrology, hydrological modelling, and climate change assessments. Melissa has experience in a wide range of climate and geographical contexts underpinning her practical professional judgement. 

Using lidar change detection to support the flooding recovery efforts in British Columbia

In November of 2021, southwestern British Columbia, Canada and northwestern Washington State were affected by a series of atmospheric rivers that caused widespread geohazards and destruction of critical infrastructure. This weather event resulted in massive precipitation leading to flooding, landslides, and debris slides that impacted many communities. Highways, pipelines, energy transmission lines, and railways all experienced damage and were inoperable – at the date of writing, some still are.

In the immediate aftermath of the event, BGC worked collaboratively with our clients to develop an understanding of the damage and chart a path to recovery. One of the many techniques we deployed was regional scale three-dimensional lidar change detection. Numerical processing can be used to quickly identify and visualize areas of topographic change where multiple lidar datasets are available for the same areas. In the case of the British Columbia atmospheric river events, BGC used airborne lidar scanning change detection to find and quantify the resulting geohazard activity, which took the form of landslides, flooding, bank erosion, and debris slides.

Working closely with our partners at McElhanney, we collected over 500 square kilometres of airborne lidar scanning data between Hope, BC and Merritt, BC. The post- atmospheric rivers data was compared to earlier datasets available from prior work for clients in the area. BGC was able to deliver digital change detection results within hours of receiving the lidar data from McElhanney using our patent processing method (patent has been allowed and is currently in the process of being granted). Results were immediately available to our clients and their partners through Cambio, our secure online platform, to support in recovery efforts. The resulting data was used to identify impacts on assets, prioritize field inspections, develop new designs, and understand future risks.

In the past year we have processed over 50,000 square kilometres of lidar change detection data, serving up tens of billions of lidar change detection points in Cambio to clients globally. We are proud that this work has been able to rapidly deliver high-value information used to save lives, reduce costs, and protect the environment.

Matthew Lato, PD.D., Eng., P.Eng. (AB, BC, ON, SK)

Innovation Lead

Matthew Lato is a Senior Engineer at BGC. His technical expertise is in the application of 3-dimensional remote sensing, specifically LiDAR and photogrammetry, for geotechnical mapping, change detection monitoring, and stability assessment and geohazard risk management. He is the lead author of the Site Investigation, Analysis, Monitoring and Treatment chapter of the Canadian Technical Guidelines and Best Practices related to Landslides, the recipient of the 2018 Canadian Geotechnical Colloquium Award, and an author or co-author of over 31 journal papers and 90 conference papers.

Supporting tailings monitoring with Cambio

Over the past few years, the ICMM has engaged with vendors and research institutions to understand systems and technology capable of supporting responsible tailings management. Click here to read the summary report produced by ICMM. One of the platforms leading in this field is BGC’s enterprise software platform, CambioTM.

The Cambio platform allows mine developers and operators to see potential problem areas before they result in serious, costly consequences. Cambio combines a cloud-based centralized knowledge base, industry leading field data collection tools and state of the art visualization to support safe tailings management and inform decisions throughout tailings facility lifecycle. Cambio directly supports TSF monitoring through integration of remote sensing (lidar, InSAR, satellite) monitoring data with in-situ (live and manual) instrumentation, lab testing data, field observations, and action tracking. Cambio is currently in use supporting day to day operations at numerous active mine sites.

  • Cambio improves understanding of the facility by bringing all data into a centralized, geospatial view.
  • Cambio reduces risk and improves accountability by making the reporting more effective and transparent.
  • 2D map based and 3D interactive collaborative environments.

Using lidar data to inform risk management decisions

In August 2020, the Grizzly Creek Fire ignited in the rugged Glenwood Canyon of central Colorado. Glenwood Canyon is considered one of the most scenic corridors on the U.S. Interstate Highway System and is a critical route for road and rail traffic across the state as well as providing recreation opportunities for hiking, biking, hunting, and river rafting. Over an approximate four-month period the fire altered forest lands along the steep canyon walls and forested connecting drainages above Interstate 70 (I-70) and the Colorado River.

The following winter provided a quiet recovery period for the canyon, but this was only temporary as the summer months in this region of Colorado generate intense thunderstorms with runoff that can overwhelm heathy drainages. Unfortunately following a forest fire, the storm runoff on burned and bare soils can be orders of magnitude more destructive. The summer monsoon season of 2021 was no exception, with several storms generating sediment laden post-wildfire debris flows that covered and damaged I-70 and the nearby Amtrak railway, deposited sediment in the Colorado River, and also stranded travelers in the canyon at times. The events resulted in weeks of highway closure for this critical corridor during the summer travel season, causing adverse economic impacts to nearby communities and measurable disruptions to interstate commerce.

Post-fire debris flow blocking the Colorado River.

To reduce the potential for future disruptions, the Colorado Department of Transportation (CDOT) engaged with BGC to understand how ground conditions are changing following the wildfire and 2021 post-fire debris flows. Through this additional understanding, CDOT can prioritize mitigation projects on the basis of greatest need and cost-benefit, while also advancing predictive models that consider the relationship between burned conditions, slope, changes in terrain, and precipitation thresholds that can lead to disruptive debris flows.

Debris flow deposition on I-70 bridge approach.

To measure continuous ground change over the entire burn area, BGC contracted with an aerial survey firm to collect and process airborne lidar for over 100 square miles (260 square kilometers) of the Glenwood Canyon and Grizzly Creek Fire area. This newly collected lidar data was processed against existing public lidar data collected in 2016. These two sets of lidar data were entered into Cambio, BGC’s software platform, to deliver an interactive lidar change detection layer across the entire burn area. This processing of change between two different lidar data sets uses a patent-pending change detection algorithm to calculate positive and negative change over this entire area. Using Cambio, this type of change detection processing can be turned around within 24 hours.

Cambio screenshot showing the ground movements following storms in the Grizzly Burn Area.

BGC continues to work with CDOT and other partner agencies, such as the United States Geological Survey, to understand how the Canyon slopes have changed after the fire and 2021 debris flow season, and to plan mitigation efforts that can be implemented in the summer of 2022 and beyond. A better understanding of the post-fire debris flow events in Glenwood Canyon may also help CDOT and other stakeholders understand their risk exposure to debris flow impacts from future burn scars.

The Geohazards paradigm is so different to what a lot of the other members of CDOT are used to being exposed to. It is often difficult to convey the severity of an event to people outside of the response, but Cambio is such a great tool to do this alongside the other utility it provides.

BEAU Taylor
Colorado Department of Transportation
Close-up Cambio screenshot showing measurement of sediment loss and deposition in the Blue Gulch Basin of Glenwood Canyon.

Mark Vessely, M.Sc., PE.

Principal Geotechnical Engineer

Mark Vessely has over 25 years of experience in geologic hazard and risk assessment, emergency response to slope and other ground movements, and design for bridge foundations, retaining walls, pavements, and slope stabilization projects.

Employee Spotlight – Kerri Bascom

Kerri Bascom was born and raised in the Bahamas. Growing up surrounded by the Atlantic Ocean Kerri has always been fascinated by the dynamic nature of coastal and riverine environments and its ability to transform the surrounding landscape. In high school she participated in the Technical Cadets Corps Program which provided a pathway to encourage students to move into the technical sector. With support from a number of people along the way, this program help set her on the path to a scholarship at Queen’s University in Kingston, Ontario where she completed her Bachelors and Masters degrees in Civil Engineering. The move from the sunny Bahamas to Eastern Canada was a huge change for her as she got to experience a true Canadian winter for the first time. Despite the cold weather, after completing her undergraduate and graduate studies, she decided to make Canada her permanent home and started her career with BGC directly out of school and is currently working towards her permanent residency.

How long have you been with BGC and what do you do here?
I’ve been with BGC for 1 year and 2 months and am currently part of the Surface Water & Pipeline teams as a Junior Civil Engineer.

How would you describe your job to a class of Kindergartners?
I work in a team which focuses on making sure that the structures we put in place years ago are ok to use now and potentially in the future.

What is your favourite thing about working at BGC?
The company culture. BGC really feels like a community. Besides connecting at work, I’ve had the opportunity to hang out outside of the office with my coworkers through activities like book club and that helps build the sense of community we have here.

What is the one piece of advice you’d give to new hires at BGC?
Don’t hesitate to reach out. Nobody knows everything so when you don’t know the answer to something, reach out and ask. When I first started here at BGC I was hesitant to reach out for help but I’ve quickly realized that seeking others’ perspective and hearing about their approach to solve a problem has really helped me do my job better.

If you could switch jobs with someone in BGC, who would it be and why?
Someone from our Data Sciences team. In university I had the chance to learn a bit about coding and really enjoyed it. The opportunity to use scripting programs like Python has always interested me.

If you could have an unlimited supply of one thing, what would it be?
Time, sometimes I feel like there’s not enough time in the day to do all the things I want to do. And this is not a matter of being overworked; I really would love more time to explore other activities and interests that I haven’t had the chance to yet like obstacle course racing.

What is the weirdest food you’ve ever eaten?
When I first moved to Canada my friends took me to try deep fried ice cream. I was confused at first, how is it possible to deep fry ice cream? It’s now become one of my favourite deserts.

What fictional place would you like to visit?
I’m a proud to say I’m a nerd and I love anime. I’d love to visit the Avatar universe specifically from The Legend of Korra.

If you had to listen to one song for the rest of your life what would it be?
Tightrope by Janelle Monae. I also really love soca music.

What is the best advice you’ve ever been given?
Don’t doubt yourself. You might not be right but don’t second guess every decision you make. Trust your gut and make an effort to be more decisive

BGC project takes home Award of Merit at the 2021 ACEC-BC Awards for Engineering Excellence

Nominated in the Soft Engineering category for our Integrated Provincial Flood and Steep Creek Assessments project, BGC was proudly awarded the 2021 Award of Merit at the April 29th ACEC-BC virtual gala. The Association of Consulting Engineering Companies British Columbia annually recognizes the outstanding accomplishments of consulting engineering companies across BC at their Awards of Engineering Excellence. We are proud to be among the 6 nominees in the Soft Engineering category this year and thrilled to have won the Award of Merit.

A winning project

Many communities in British Columbia and beyond have long histories of living with geohazards, which have led to economic loss, interruption of transportation corridors and sometimes loss of life. Despite the high cost of responding to such disasters, siloed local funding structures, knowledge gaps, and divisions of government responsibility have created challenges for pro-active risk management that, if resolved, could transform how we reduce risk in places where people live and work.

Over the past three years, BGC has been working with local governments and partners to assess geohazards across 300,000 km2 of BC. By integrating knowledge, tools, multiple funding sources, and approaches across jurisdictions, our goal is to create a stronger path to risk reduction than any single authority could accomplish in isolation. Our integrated flood and steep creek assessments, delivered via Cambio™ and through the efforts of over 60 team members, helped support proactive geohazard risk management in southern BC communities.

We prioritize hazards areas using the principles of risk assessment, considering how often a damaging event can occur and what the likely damage would be. To support a long-term vision for natural hazard risk reduction planning, implementation and monitoring, BGC also completes detailed follow-up assessments. This work is backed by our unique web-based solution, Cambio™, that provides data organization, prioritization analysis, results communication and on-going geohazard management.

With over 10,000 prioritized geohazard areas and hazard susceptibility modelling completed across tens of thousands of watersheds, this work is BC’s most extensive flood and steep creek geohazards assessment to date. Our study results and supporting software will help government partners tasked with long-term geohazard risk-informed development planning, bylaw enforcement, flood resiliency and emergency response planning.