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.