Following a beaver dam breach that caused significant flooding along Steenburg Lake North Road at McGeachie Conservation area on August 11, 2024, SLCA president Joanne Burghardt reached out to Crowe Valley Conservation Authority General Manager Tim Pidduck to ask questions about the incident.
Tim Pidduck, General Manager
Crowe Valley Conservation
“The Crowe Valley Conservation Authority (CVCA) was notified of a beaver dam break north of Steenburg Lake early on the 12th of August 2024 resulting in a deluge of water entering the lake.
“These natural events do occur throughout our watershed at various times of the year and are relatively common, especially during periods of high water in the spring when a number of factors determine when or if a beaver dam break will occur.
“This dam break occurred during the summer season during a storm event that swept through most of Eastern Ontario. Although the total amount of precipitation was considerably less than expected, in all likelihood, other conditions leading up to the failure were a factor as well. This could include any one of or a combination of the age of the dam, its height, water pressure exerting on the structure, wave action due to the storm wind, high water levels prior to the storm, maintenance issues (was the dam abandoned due to predation or other causes such as old age, illness, injury or even territorial dispute) or was it already in a weakened state due to other natural causes or even human intervention. Without any evidence, the cause of the dam failure will never be known, unlike structures built by humans who must find out why a structure failed.
“CVCA staff have estimated the amount of water released into Steenburg Lake was approximately 2.3 – 2.5 million cubic feet of stored water behind the dam. There would have been additional water from the flow of the creek itself, which is virtually impossible to measure without an hydraulic analysis of the creek. Suffice to say, it was a large volume of water that unexpectedly occurred without any warning causing damage and disruption at the point it entered Steenburg Lake.
“The level is certainly high and CVCA staff have confirmed the lake rose approximately 17.5 cm (7 inches) due to the flow from the dam and the recent rainfall on the weekend. The lake is dropping and should start to resemble normal conditions within 7 to 10 days. However, this will depend on how much additional rainfall is received in the area during this post beaver dam break and when it occurs. Approximately 30 to 35 mm is expected this weekend, therefore it may reduce the lowering of the lake than what staff have estimated.
“Presumably there was a significant amount of silt, potentially some natural detritus material and likely some human garbage (hopefully very little) from the sudden surge of water. Depending on what contaminants were being stored in the silt and the volume released into the lake will determine if there are any environmental concerns. Testing and monitoring conducted for a period of time would likely be required to gauge what the effects would be on the ecosystem. Unfortunately, the CVCA does not have the staff or resources to complete this type of work to determine if there is any risk to the lake’s ecosystem.
“The CVCA has owned the McGeachie Conservation Area since the mid- 1990’s. The dam break at this location has happened twice in the approximately 30 years of ownership, which may or may not coincide with the natural beaver pond/dam break/beaver meadow cycle.”
Note: The SLCA Board will continue its regular water testing routine, and will reach out to the CVCA to determine if there is further testing we should do to monitor the effect of the dam breach on the lake’s ecosystem. – Joanne Burghardt, President SLCA, Aug. 16, 2024.