The Village of Lebret is located 70 kilometres northeast of Regina, along Mission Lake in the picturesque Qu’Appelle Valley. Popular with tourists and cottage owners, Lebret is also home to residents and commercial developments. Heavy spring runoffs present an annual flooding threat to communities in the valley. High water levels and accompanying wave effects (wave setup and run-up) can present a significant flood risk. The most recent flood occurred in 2011 – a 1:100-year flood event. 

Lebret had a flood hazard map in place, developed by the provincial Water Security Agency (WSA) in 2013 to mitigate risk to citizens and property. The map defines and regulates land which cannot be developed (the floodway) and which can be developed, provided that certain measures are taken (the flood fringe). The result was only a relatively small flood fringe area within the Village’s jurisdiction could ever be developed.

Although appropriate methods were used at the time for flood hazard mapping, the Village felt the map needed updating to better delineate the flood fringe, which would protect public safety and property, and could allow for greater land development. In 2021, Lebret engaged Associated Engineering to develop a revised flood hazard plan using today’s advanced analysis and methodologies. 

Using coastal modelling techniques and wave analysis expertise supported developing a reliable flood hazard map

The prime project challenge was the tight timeline. The plan required a detailed bathymetric survey of the lake depths to be completed using a boat in November 2021, before lake freeze-up. All work, which was half funded by the WSA, had to be completed by March 31. The team had to proactively plan, quickly act, acquire information, and identify possible solutions for analysis without delay. The project required a collaborative relationship between the Village of Lebret and the WSA (a key regulatory stakeholder and funding agent). The timeline required that the regulatory approval process be streamlined, so the Associated Engineering team obtained buy-in on the process and results at every project meeting.

To complete the work, we used bathymetric readings, a LiDAR survey, wind and wave analysis, and the 1:100 and 1:500-year flood levels from the WSA. Working in collaboration with WSA, we adapted advanced coastal modelling techniques and leveraged our expertise in wave analysis to develop detailed, reliable flood hazard mapping.

Project Manager, Daryl Brown, shares, “To our knowledge, adoption of coastal technology and models for flood mapping – combining wind and wave action – has not previously been undertaken in the Prairies. This process was key to completing the work on time, with the desired level of accuracy and reliability. This innovative model where wave action is a consideration for public safety and property development can also be applied to other Prairie communities.”

Completed on time and on budget, the new flood hazard map provides Lebret with assurance of the areas that the community can securely develop, while protecting public safety.

The post Revised Flood Hazard Map allows Village of Lebret to manage future land development and protect public safety first appeared on Associated Engineering.

November 2021 saw a series of atmospheric rivers (heavy rainfall events) in southwestern BC, which resulted in extreme flooding of many communities. Associated Engineering received numerous requests for flood management assistance from various provincial agencies and municipalities. Our specialists in water resources, transportation, environmental management, water quality, hydrogeology, community resilience, and emergency response and recovery responded to our clients’ urgent calls for support. 

Our staff responded swiftly, travelling to locations along Highways 1, 3, 5, and 7, as well as secondary roadways and other sites throughout the Fraser Valley and the BC Interior. They assessed major bridge and culvert washouts, channel avulsions, and general flooding and erosion issues. Our team also played a key coordination role with Emergency Management BC in their Emergency Operations Centre. These efforts have continued with recovery activities in early 2022, as permanent repairs are required for flood-damaged infrastructure.

Senior Water Resources Engineer, Geoffrey Cahill, led our emergency flood response efforts for the City of Merritt following the Coldwater River flood of November 15. This was a large event and is now the flood of record for the area. Flood extents in Merritt were vast, causing dike breaches, dike and bank overtopping, two avulsions, a bridge failure, and extensive overland flooding. The city’s wastewater treatment plant was compromised and the FortisBC gas main supplying the city was scoured and suspended in the new avulsion channel. This led to an evacuation order for the City of Merritt’s 7000 residents. 

“We provided an emergency channel assessment and design recommendation for a river diversion to put the Coldwater River flow back in the pre-event channel.” 

Our team then completed rapid dike inspections, with the threat of further atmospheric river events, and provided recommendations for emergency dike repairs, temporary works (HESCO Barriers and Tiger Dams), vehicle and trailer removals from the river, and a second river diversion. In addition, we provided hydrotechnical engineering guidance to the City’s Emergency Operations Centre, field reviews of all dike and bank repairs, and construction oversight at 12 sites, working in collaboration with ten contractors and the Canadian Armed Forces. 

On the weekend of November 28, Associated Engineering received a request from Emergency Management BC and the BC Ministry of Transportation and Infrastructure to assist in closing a gap in the flood protection infrastructure along Highway 1 at the Sumas River crossing in Abbotsford, BC. 

Jamie Fitzgerald, Manager, Water Resources, tells us, “Our staff immediately attended the site and identified the required flood protection measures.” We provided flood management and structural engineering advice and collaborated with the military, Ministry of Transportation and Infrastructure, Abbotsford Fire Department, and local contractors. A Tiger Dam representative was also on-site and provided assembly instructions to the team. As a result of their efforts, the Tiger Dam was successfully assembled by 5 am on November 29. 

The Associated Engineering team continues to support the City of Merritt and the BC Ministry of Transportation & Infrastructure with their flood recovery efforts 

Associated Engineering staff involved in the emergency response and recovery efforts on the engineering services include Jamie Fitzgerald, Trevor Friedmann, Nate Antonides, Michael MacLatchy, Kyle Eckart, Eric Finney, Geoffrey Cahill, Carly Davis, John van der Eerden, Chris Duncan, Andrew Wiens, Matt Bowen, Shawn Bidulka, Amr Mohamed, Pat Stancombe, Matt du Toit, Shane Cook, Katrin Habel, Mike Lumb, Ethan Wilkinson, David Harvey, Nik Cuperlovic, Marta Green, Matt Lozie, and several others active in the field monitoring ongoing construction activities.

The post Timely response and support for worst flooding in BC’s history helps accelerate community restoration and protect vital infrastructure from further damage first appeared on Associated Engineering.

In recent years, the City of Lethbridge has experienced several significant rainfall events, resulting in roadway flooding and damage to infrastructure in Alberta’s fourth largest city. Extreme rain events in 2020 further highlighted areas prone to flooding and the need for operational improvements to the City’s stormwater management system.

The City’s stormwater infrastructure consists of approximately 465 kilometres of stormwater pipe, 6,000 stormwater manholes, and many stormwater management facilities. To better understand and help plan for improvements to their stormwater management system, the City of Lethbridge wanted to develop a stormwater model of the system, and retained Associated Engineering to undertake this work. 

Our approach allows the team to focus additional effort on quality control and quality assurance of the models, as well as interpretation of model results

Project Manager, Adam McDonald, tells us, “The City sought the ability to evaluate their stormwater management system against design rainfall events to determine the conditions contributing to flooding. They also wanted to be able to confirm drainage capacities in new areas being developed, and where new areas will be connecting to the existing system.”

Our team’s tasks included data collection and review; development of a geographic information system (GIS) data model and model development templates; data quality control; design rainfall event selection and design; climate change rainfall forecast; development of existing system one-dimension by one-dimension drainage models; quality assurance and quality control reviews; existing system analysis and risk assessment; development of improvement concepts for five top-ranked locations; cost estimates; and reporting.

Model files are large in scope and incorporate all of the drainage infrastructure. As a result, the full City of Lethbridge model has been divided into separate models to streamline model run times. 

The development of detailed stormwater management models using traditional methods is an extremely labour intensive exercise. Associated Engineering’s approach uses GIS tools and programming to facilitate development of key parts of the model. Associated’s team developed one-dimension by one-dimension (1D-1D), dual drainage models of the City’s drainage system, analyzing stormwater flow in the storm sewer system as well as surface drainage. The models needed to cover all of Lethbridge and be sufficiently detailed to predict flooding due to minor system (e.g. gutters, catch basins, and storm sewers) surcharge and major system flows (e.g. streets, streams, channels, and ponds).

Adam explains, “The model development required significant data analysis and pre-processing to verify data.” As a value-added exercise, Associated Engineering committed to additional data input, feature digitization, and GIS quality control.

“Our project team developed automated custom queries for GIS data processing, comparing the data by proximity to help identify and flag any issues. Any missing data was interpolated and flagged for future identification.”

Throughout the project, the team looked for opportunities to further refine our standardized approach to model building and made significant improvements to the GIS programming that is used to streamline the process.

The model results were validated against anecdotal information of historical flooding, matched known flooding locations, and, in some cases, the results of other stormwater models which provided confidence in the accuracy of results produced.

Climate change adaptation was a key consideration on the project. The team provided the City with models that incorporate the design rain events, as well as historical return frequency events, and forecasted climate change events. The forecasted climate change rainfall events will enable the City to quantify the requirements to manage current and future flood risk affected by climate change impacts. 

The team also identified five areas for improvements to mitigate flooding. To assist the City with prioritizing improvements, we recommended that the City work with stakeholders to develop a customized definition of the preferred level of service for each area, based on a triple bottom line approach. The existing system models should then be used to develop a master drainage plan that takes a holistic look at flood risk and mitigation plans and thus inform investment in infrastructure and capital expenditures.

The project is in its final stages, and will be complete early in 2022. Our key personnel on this project included Adam McDonald, Andrew Rushworth, Carmen Janzen, and Laurel Richards. 

The post Predictive citywide stormwater models help protect Lethbridge’s infrastructure first appeared on Associated Engineering.

A series of heavy rainfall events in southwestern BC in November resulted in devastating flooding. Subsequently, Associated received many requests for assistance from provincial agencies and municipalities. Staff from several offices and diverse disciplines, including water resources, transportation, and environmental, responded to these urgent calls from our clients.

Members of our staff deployed to Highways 1, 3, 5, 7, secondary roadways, and other sites throughout the Fraser Valley and in the BC Interior to assess major bridge and culvert washouts, channel avulsions, and flooding and erosion issues. Associated also played a key coordination role supporting Emergency Management BC’s Emergency Operations Centre.

Associated provided emergency flood response for the City of Merritt following the Coldwater River flood that occurred on November 15, 2021. This event is now the flood of record and roughly doubled the previous 200-year estimate. Flood extents in the City were vast, causing dike breaches, dike and bank overtopping, two avulsions, a bridge failure, and extensive overland flooding. The City’s wastewater treatment plant was compromised and the FortisBC gas main supplying the City was scoured and suspended in the new avulsion channel. This all led to an evacuation order of the entire City.

Associated conducted an emergency channel assessment and recommended a design for a river diversion to put the Coldwater River flow back in the pre-event channel. Rapid dike inspections were then completed with the threat of further atmospheric river events, and recommendations were provided for emergency dike repairs, temporary works (HESCO Barriers and Tiger Dams), vehicle and trailer removals from the river, and a second river diversion. Associated provided hydrotechnical engineering guidance to the City’s Emergency Operations Centre, field reviews of all dike and bank repairs, and construction oversight at 12 sites with 10 contractors and the Canadian Armed Forces.

On Sunday, November 28, Associated received a request from Emergency Management BC and the BC Ministry of Transportation and Infrastructure to assist in closing a gap in the flood protection infrastructure along Highway 1 at the Sumas River crossing in Abbotsford, BC. Associated staff immediately attended the site and identified the required flood protection measures. We provided direction to the Military, the Ministry, Abbotsford Fire Department, and local contractors. A Tiger Dam representative provided assembly instructions to the team.

The team worked through the night to complete a 1.5 metre high Tiger Dam, approximately 100 metres long, to close the gap between the recently raised Sumas River dikes to the north and south of the highway. The Tiger Dam was assembled by 5 am on November 29. 

Thanks to our team who worked through the night/weekend to support the installation of flood protection measures.

The post BC Flood Protection Support first appeared on Associated Engineering.